Contents
Section 1: Introduction - Rational of Mammographic
Screening
Section 2: Physical Principles of Mammography and Basic
Limitations
Section 3: Evaluation of Masses
Section 4: Evaluation of Calcifications
Section 5: Evaluation of associated structural changes
Section 6: Location of lesions in the breast
Section 1:
Introduction - Rational of Mammographic Screening
Breast cancer is
among the most common and deadly of all cancers, occurring in nearly one
in ten women. Mammography is a uniquely important type of medical imaging
used to screen healthy women for small curable breast cancers. Controlled
medical studies have shown that mammography can lead to decreases in death
due to breast cancer sufficient to measurably lengthen life. The reported
cancer free 5 year survival for cancer detected by mammography is 92%,
with 96% overall 5 year survival.
Rational for
Standardized interpretation, and reporting:
Because mammographic
screening procedures are applied to all persons at risk, millions of
mammograms, and hundreds of thousands of biopsies must be preformed. To
minimize the natural anxiety and inconvenience, mammographic procedures
must be quick and accessable, and every effort must be made to inform,
council and support women undergoing the procedure.
Breast care involves
many physicians, personal physicians who order mammograms, radiologists
who interpret mammograms and do needle biopsies, surgeons who preform
incisional biopsies and curative cancer operations, pathologists who
interpret biopsies, and radiotherpists who deliver radiation treatment.
Patients often must function under great stress, in evaluating several
physician recommendations to make important treatment decisions.
Since breast care involves so many people, clear and accurate
communication is almost as important as technical competence. To
facilitate communication, the America College of Radiology (ACR) has
created a standardized system reporting the results of mammography. We
feel this system provides a clear and accurate approach to mammographic
interpretation. The system is called ACR - Breast Imaging Reporting and
Data System, or BIRADS. It includes standard interpretation and reporting
formats, a standard dictionary of terms, and standard disease
classifications used in checking program effectiveness.
This presentation will cover the basic principals of mammographic
interpretation, described in the terms defined by ACR - BIRADS.
Section 2:
Physical Principles of Mammography and Basic Limitations
Basic
Physics of Mammography:
X-ray images depend on differences in x-ray stopping power (attenuation)
to separate tissues. In general, a clear separation between normal
functioning tissue, and abnormal cancerous tissues is not possible since
their attenuation if very similar. However both functional tissue and
cancer can be separated from fatty storage tissues which normally surround
active breast tissue, even in lean persons. This is due to a substantially
lower attenuation caused by fat.
In older women, the functional glandular tissue diminishes, leaving only
thin supporting tissues clearly outlined by fatty tissues. Mammography in
these "mature" breasts is very effective, since even small cancers are
well outlined by fat. In addition, many cancers develop calcium deposits
which strongly stop X-rays and are easily seen on mammograms.
Basic
Limitations of Mammography:
Since mammography cannot separate normal gland tissue from tumors, it is
much more effective when gland tissue diminishes with age. Many women
retain glandular tissue as they "mature", and it camouflages tumors until
they are large. As you might expect, the young women's breast normally
contains more active tissue, which again interferes with detection of
small cancers.
Breast
Composition Determination:
The ACR-BIRAD system recognizes this limitation by reporting the
background composition of the breast in categories:
1.) Almost Entirely Fatty: Mammography very effective, sensitive to even
small tumors.
2.) Scattered Fibroglandular tissue: Minor decrease in sensitivity.
3.) Heterogeneously Dense tissue present: moderate decrease in
sensitivity.
4.) Extremely dense tissue present: marked decrease in sensitivity.
Mammography does retain some value even in dense breasts, by detecting
calcium deposits (which are so dense, surrounding tissue does not
interfere), but is not reliable in detecting small non-calcified cancers.
In general, women with "dense" breasts remain so from year to year, and it
is possible to let a women know when she cannot depend on mammography. In
dense breasts, more emphasis on self-examination may be appropriate,
particularly if there is a family history of breast cancer.
Examples:
In image 1, fatty replacement allows a tiny cancer to be seen, such a
small tumor would not be appreciated in Image 2, where dense glandular
tissue is present.
Image 1: Small 5mm Cancer in Fatty Breast Image 2: Dense Breast: tissue
obscures detail.
Section 3:
Evaluation of Masses
Definition
of mammographic masses:
The presence of a localized collection of tissue represents a mass. By
ACR-BIRAD definition, a mass is a space occupying lesion seen in 2
different projections (X-ray points of view). When an apparent collection
is seen in only one view, it is referred to as a mammographic "density".
Although the density may be a mass, prehaps obscured by overlying
glandular tissue on other views, it may be nothing more than several
overlapping more normal areas.
When a mass is seen (confirmed on two views), it is characterized to
determine if enough maligant features are present to justify biopsy or
removal.
When a density is seen (seen on only one view), additional views must be
done to confirm or exclude the presence of a mass. This may mean asking
the patient to return. If a mass is confirmed, further characterization to
decide about biopsy is indicated.
Mammography shows
three important characteristics of masses:
1.) Shape
Shape Analysis of
masses seen in mammography.
General shape of a mass is relatively non-specific since both benign and
malignant processes tend to arise from one spot and grow
circumferentially. Round and oval shapes are associated with benign
processes in part because they imply a well circumscribed margin, a benign
sign considered in the margins section.
Round, oval, and
lobular shape:
Masses in these
catagories imply a well defined smooth edge which is often benign. If
their margin is not smooth, their shape alone does not tend to exclude
malignancy.
On the left the oval mass is actually reniform (kidney bean shape) with
circumscribed margin of a benign node. On the right, an oval mass with an
finely irregular margin (microlobulated), is infilrating cancer, it is the
margin not the shape that differentiates these two masses.
Irregular
shape:
Irregular shapes are more concerning, in part because it implys indistinct
margins which are more often malignant (tumor infiltrating edges).
Processes that scar the breast are often irregular.
On the left, the
irregular shape (with indistinct margin) of a small infiltrating cancer.
The irregular shape implys extension into surrounding tissue, a common
means of cancer infiltration, although benign processes such as scarring
may show irregular borders.
Architectural Distortion:
In this class, the normal outline of tissues is distorted, sometimes with
no definable mass. It includes spiculations (lines radiating from a
center), retraction (puckering) of normal connective tissue lines.
It is important because cancer infiltration often occurs along normal
tissue planes, where is causes abnormal stiffness or contraction which can
sometimes be seen before an actual mass. It is important to do as many
special view as needed to establish the finding, as unexplained
architectural distortion usually merits biopsy even when no mass is
evident.
In addtion to cancer, architectual distortion occurs with healing after
injury including previous biopsy, so it is critical to determine if the
area has been injured.
Benign causes of architectual distortion such as scarring tend to remain
unchanged or improve, so whenever previous mammograms have been done, it
is most important to compare to see if changes have really occurred.
Examples of malignant architectural distortion. On left, a malignant mass
puckers the overlying skin as it invades. On the right a small cancer
draws adjacent tissue into concave or scalloped margins as it invades.
Special Shapes
(special cases):
Tubular
Density/Dilated Duct:
Branching tubular structures usually represent enlarged ducts (milk
ducts). If they are clearly identified as such, and no other findings are
evident, these densities are of little concern.
Intramammary Lymph Node:
Typical lymph nodes are circumscribed, reniform (kidny bean shape), and
often have a fatty notch and center (hilum area of lymph node). Usually
less than 1 cm, and usually seen in the outer, often upper part of the
breast. When these characteristics, particularly fatty center or notch are
well seen, the lesion is almost allways and benign and insignificant node.
Intramammary nodes: Circumscribed margins, fatty notch or fatty central
hilum. They may appear as small nodules clustered around the fatty center.
Asymmetric Breast Tissue:
Breast tissue is usually very similar from one side to the other. When a
greater volume or density of tissue is present on one side, concern arises
even if no mass is seen. Although asymmetry does occur as an occasional
normal finding, it is important to obtain detailed views, usually with
small "focal compression" devices to spread tissues out and exclude a
mass. Even if no mass is identified, accelerated follow-up mammogram in 6
months time is usual. If the area can be palpated (felt), biopsy must be
considered. Once asymmetry is identified, it tends to remain constant over
years, so comparison with previous mammograms can be reassuring in such
cases.
Focal Asymmetric Density:
This is an area of breast density (tissue) with similar shape on two
views, but completely lacking borders and conspicuity of a true mass. It
must be carefully evaluated with special views (usually "focal
compression" once again) to exclude finds of a true mass or architectural
distortion. If no specific findings are evident, it is managed as
asymmetric tissue, comparison to old mammograms if availible, short
interval follow-up if not. If special views show mass like character, or
if the area can be palpated (felt), biopsy must be considered.
Margins
Margin Analysis of
masses seen in mammography: Margin analysis is characterization of the
edge or transition between a mass and surrounding normal fatty tissue. Its
importance lies in the tendancy of invasive cancer to infiltrate adjacent
tissue, which results in an indistinct or frankly spiculated appearence.
The following types of margins are described in the BIRAD standard. The
usual interpretation is listed in parenthesis.
Circumscribed or well-defined or sharply-defined margin (probable benign
class): The margins are sharply demarcated with an abrupt transition
between the lesion and the surrounding tissue. There is nothing to suggest
infiltration. Because invasion may be microscopic in scale, the most
detailed mammograms are needed to fully characterize this margin. These
detailed views are called focal magnification, because they enlarge the
image of a small area of tissue.
Circumscribed margins are a very reassurring characteristic since if a
mass is circumscribed (as shown on two high quality focal magnification
views) and has no suspicious calcium deposits, 98% to 99% will be benign.
Examples of circumscribed masses. Even on highly magnified images, the
edges remain sharp all the way around the mass. These particular examples
are lymph nodes also showing the characteristic notched shape.
Management of circumscribed masses:
Since so few are cancer, it is usual to defer biopsy in favor of
rechecking mammography every 6 months for 2 years (watchful waiting). In
nearly 95% of cases, recheck shows no growth and biopsy is avoided. In 2-3
%, a benign process grows, and requires biopsy establish its nature. In
the 1-2 % that are cancer, growth is seen on follow-up, and biopsy
intiates treatment. Although some time is lost in the process, the cancers
found at follow-up are usually still small and curable.
Circumscibed masses are very common, seen in about 10% of mammograms.
Stratagies to avoid biopsy of such masses are important to prevent a very
large number of biopsies.
Circumscibed masses are most often either fibroadenoma (benign tumor),
lymph node, or simple cysts (thin walled fluid collections). When a
circumscribed mass is first noted, an ultrasound test may be ordered which
can identify simple cysts. This is helpful because simple cysts (as
diagnosed by ultrasound) are almost never cancer, and may not even need
special follow-up mammograms. If the ultrasound shows a solid (fleshy)
circumscribed mass, follow-up is required.
Another option used with circumscibed masses is stereotactic core needle
biopsy. In this procedure special x-ray systems guide a needle passed
through the skin into the mass to remove several small biopsy samples.
This biopsy is safe, fairly quick, and causes little pain. It has been
shown to be as accurate as surgical biopsy in finding cancer. At this time
there are no controlled studies to prove these biopsies in the tumor site
do not spread cancer cells, though this risk is widely believed to be
insignificant. Needle biopsy is often the choice of patients who are
unwilling to accept any risk related to waiting.
Microlobulated
margin (suspicous class):
In these masses the edge undulates with short, fine cycles producing small
undulations. The unmagnified image often appears circumscribed, but
carefull magnification shows the undulation. This is important because
microlobulated margins are often associated with invasive cancer and are
suspicious enough to merit biopsy.
.
On the left, magnified image of microlobulated mass (suspicious) caused by
infiltrating ductal carcinoma, compare to circumscribed margin of benign
lymph node on right. Carefull magnification views are need to see the
difference, and should be done before a circumscribed (probable benign)
description is made.
Obscured Margins
(indeterminate, need further views): In this case, a part of a mass is
seen, part of the mass has a circumscribed margin, but some or perhaps
most of the margin is covered by overlying tissue, creating an indistinct
margin. In this case, is is frequently possible to move the extraneous
tissue using special views (focal compression view, tissue roll view),
which allow a completely circumscribed (probable benign-watchful waiting)
margin to be seen. If a complete circumscribed margin cannot be found, the
massmust be considered suspicious (consider biopsy).
Above left, the right and left margin are circumscribed, but the upper and
lower margin are obscured. Above right, lower and right margins
circumscribed, left and upper margins obscured. Further views were used to
show these benign fibroadenomas was circumscribed (probable benign). These
particular patients decided to have biopsies. Indistinct or Ill-defined
Margins (suspicous, consider biopsy):
In these masses at
least part of the margin is indistinct, but the cause cannot be shown to
be overlying tissue. Masses in this group may be benign, but there are
enough cancers to make it worthwhile to do a biopsy. The benign masses in
this group may be ill-defined because of inflammation, scarring, or
obscurring tissue. The cancers are ill-defined due to the process of
infiltrating cancer spread.
Above, a small (5mm)
infiltrating ductal cancer with indistinct margins, particularly at the
right and lower margin.
Spiculated margins
(suggestive of malignancy, biopsy should be considered):
These masses are
characterized by lines radiating from the margins of the mass. In cancer,
these represent small fingers of cancer spreading outward along the normal
fascial planes of the breast. Although many of these lesions are cancer,
some will be found to be scars (from old injury or surgery) or inflamation
such as sclerosing adenosis.
When this finding is seen without an appreciable mass, it is called
archituctual distortion, and is still a justification for biopsy.
Above left, spiculated and indistinct margin in a small infitrating
lobular carcinoma. Above right, spiculated and indistinct margin of
infiltrating ductal carcinoma. This appearence is very suspicous, and
biopsy must be done. If previous biopsy has been done, a sequence of
mammograms showing the developement of a scar with progressive decrease in
size can obviate biopsy.
3) Density
Density Analysis
of masses seen at mammography:
The density or
degree of X-ray attenuation is defined relative to the expected
attenuation of an equal volume of normal glanular tissue of the breast. It
is important because most breast cancers that form a mass appear to have
attenuation equal to or greater thatn the surrounding fibroglandular
tissue.
Cancer shows high density because the cancer is firm and resists being
compressed as thinly as normal tissue, and thus remains thicker and denser
than surroundings, even with focal compression views.
The tendancy to stand-out is may be helpful in finding the tumor in a
dense breast.
It is rare (though not impossible) for breast cancers to appear as lower
density. Breast cancers are never fatty (radiolucent) in character, though
they may trap fat. Central lucency is a particularly useful sign or benign
lymph nodes.
Density can be very helpful, but can be confusing when a large amount of
background tissue is present. It must be used carefully in combination
with margin analysis.
The density
catagories used are:
High density: clearly higher than surrounding, suspicious.
Equal density: density not appreaciably different, neutral significance.
Low density: density lower, but not fat containing, neutral significance.
Fat containing:
Radiolucent. This includes all lesions containing fat such as oil cyst,
lipoma, galactocele, hamartoma or fibrolipoma. This is a benign finding
unless other characteristics are suspicous.
This image of an
intramammary node is clearly less dense in its center then at its margin.
The central lucency arises from the fibro-fatty core of the node and is a
reassuring observation.
Section 4:
Evaluation of Calcifications
Introduction to
analysis of mammographic calcifications:
Suspicious
calcifcations occur in about one-third of breast cancers, and may develop
prior to the invasive phase of tumor growth (in situ cancer) when cancers
are most curable. Calcium deposits are easy to see by x-ray because they
are much denser (higher x-ray stopping power) then all types of soft
tissues in the breast. They can be seen even when large amounts of normal
glanduar tissue is present ("dense breasts").
However
calcifications also commonly occur in benign breast processes, where they
may be confused with cancer. Benign calcifications are usually larger that
calcifications associated with malignancy. They are usually coarser, often
round with smooth margins and are much more easily seen.
Calcifications
associated with cancer are usually very small and often require the use of
a magnifying glass to see well. It is also helpful to preform special
mammographic magnification view to obtain the best possible view of the
shape the the deposits.
The distribution and
number of calcifications is often helpful and should be carefully noted.
Although some
calcifications are quite typically benign, and some are quite typically
malignant, intermediate forms are common. When the specific disease
causing the calcification is not evident, the morphology (shape) and
distribution should be carefully described. Although description of benign
calcifications may not always be nesseccary, any calcifications which
might
be misinterpreted should be described.
Types and
Distribution of calcification:
1.) Typically benign
forms:
a.) Skin
calcifications: These are typical lucent centered (less dense in
center than margin) that are pathognomonic (appearence is always benign).
Atypical forms may be confirmed by special tangential skin view which show
a
position in the skin.
Typical skin
calcifications, dense, smooth, with a donut like lucent center when viewed
with magnification. They are situated in the skin and result from calcium
deposits in hair follicles. They are more common in the center of the
chest at the inner edge of the breast.
b.) Vascular
calcifications: Parallel paired tracks, or linear tubular calcifications
that are clearly associated with calcification of small arteries.
Magnification may often be helpful to delineate the paired or railway
track appearence.
On the lower border
of the left image, the dense paired and tubular lines of cacification
represent arteriosclerotic calcification in the wall of a small artery.
Across the upper border of the right image, less dense parallel lines of
arterial calcification (in the center, a small skin calcification
is also seen.
c.) Coarse or
popcorn like calcification: Here classic rounded groups of course
calcifications develope in an involuting fibroadenoma. When completely
developed, the appearence is reliable, but during early phases of
development, calcifications in fibroadenomas may be suspicious.
d.) Large rod shaped calcification: These are benign calcifications
forming
continuous rods that may occasionally branch. They are usually more than 1
mm in diameter, may have lucent center, if calcium surrounds rather than
fills an enlarged duct. These kinds of calcifications are found in
secreatory disease, "plasma cell mastitis, and duct ectasia.
Large rod shaped
cacifications, multiple, sometimes branching and symetric in many cases.
Note the dense, smooth, thick character that distinguishs these from the
much softer, irregular, smaller calcifications of intraductal cancer.
e.) Round
Calcifications: When multiple, they may vary in size. They are usually
considered benign and when small ( under 1 mm.), the term punctate may be
used. They are smooth, dense and round.
Round calcifications, dense larger and smooth.
f.) Spherical or
lucent centered calcifications: There are benign calcifications that range
form under 1 mm to over a centimeter. These deposits have smooth surfaces,
are round or oval, and tend to have a lucent center. The wall is thicker
than "eggshell" forms. They arise from areas of fat necrosis, calcified
duct debris, and occasional fibroadenoma.
umen of a duct
involved irregularly by breast cancer.
Calcification Distribution Modifiers:
Because breast cancer frequently spreads locally in characteristic
patterns, the significance of groups is influenced by the pattern of
distribution. These patterns are used as modifiers of the basic
morphologic description and describe the arrangement of the
calcifications. Multiple similar groups may be indicated when there is
more than one group that show similar morphology and distribution.
a.) Grouped or Clustered:
(Historically, the term clustered has cannoted suspicion, the term shall
now be used as a neutral distribution modifier and may reflect benign or
malignant processes): The term is used when multiple small calcifications
occupy a small volume of tissue (less than two cc.).
b.) Linear:
Calcifications arrayed in a line that may have branch points.
c.) Segmental:
These are worrisome in that their distribution suggests deposits in a duct
and its branches raising the possiblity of multifocal breast cancer in a
lobe or segment of the breast. Although benign causes of segmental
calcifications exist such as "secreatory disease: this distribution is of
greater concern when the morphology of the calcifications is not
specifically benign.
d.) Regional:
These are calcifications scattered in a large volume of breast tissue not
necessarily conforming to a duct distribution that are likely benign, but
are not everywhere in the breast, and do not fit the other more suspicous
catagories.
e.) Diffuse/Scattered:
These are calcifications that are distributed randomly throughout the
breast.
f.)Multiple groups: Multiple groups may be indicated when there is more
than one group of calcifications that are similar in morphology and
distribution.
Evaluation of
Associated Structural Changes in the breast:
These are changes
that may occur alone or more commonly in the tissues surrounding masses or
calcifications. Many are suspicious in that they imply a process which is
infiltrating and altering the character of adjacent tissues (1-6).
Category 7 - Skin lesion is a benign finding.
1.) Skin retraction:
The skin appears to be pulled or tethered into an abnormality. This is a
common finding in more advanced infiltrative cancers, but can also occur
with scarring due to previous injury or biopsy. In addition to a careful
history to identify any previous injury, previous mammograms can be very
helpful if they demonstrate the skin retraction is a long standing finding
due to scarring, and not a recent result of infiltration.
2.) Nipple
retraction: The nipple is pulled in or inverted. This can be seen as
another sign of advanced cancer infiltration, but is also a fairly common
observation in otherwise normal patients. Previous studies documenting
stability, and the lack of an underlying mass are factors which can reduce
the concern regarding this finding. It is important to exam the underlying
area carefully however to look for architectural distortion which can
indicate a tumor even in the absence of a mass.
3.) Skin thickening:
When diffuse this is often related to other systemic problems. When
localized, it may result from direct infiltration, or tumor blockage of
local lymphatic drainage. As with 1 and 2, the absence of change, and the
absence of an associated mass reduce the importance of this finding.
4.) Trabecular
thickening: This is focal thickening of fibrous septae in the breast. It
raises question of infiltration particularly in association with mass.
5.) Axillary
Adenopathy: Enlarged non-fatty lymph nodes in the axilla may be commented
on. Because the enlargement may be due to inflammatory involvement in the
upper extremity or breast, attributing enlargement to breast malignancy is
often unreliable.
6.) Architectural
Distortion: When disturbance in the course and shape of the normal
trebecular architecture is seen, particularly if it persists with directed
focal compression views, the possibility of infiltration should be
entertained. This is a finding in itself if no mass is seen, and is a
associated finding when distorted or retracted tissues are seen
surrounding a mass or other finding.
7.) Skin Lesion:
This is a mammographic finding projects from skin over breast in two
views. It is almost never associated with breast cancer, but may simulate
a mass. Careful positioning with special tangential views are used to
prove the benign skin location.
To the right is a lucent centered calcification, smooth, thick and round.
(to the left is an eggshell calcification.
g.) Eggshell of rim
calcifications: These are very thin benign calcifications that appear as
thin circular rims.
An eggshell
calcification, with a fine rim of calcifcation around its edge. A typical
benign appearance.
h.) Milk of calcium
calcifications: These benign calcifications arise a sedimented calcium
containing fluid in small cysts. When view vertically (from the top) the
fluid creates a smudged and poorly defined appearence which may be
somewhat suspicious. When view with a horizontal x-ray beam however, the
fluid creats a flat fluid level like a partially filled teacup confirming
their benign nature.
On the left, vertical image shows smudged indistinct appearence. On the
right, well defined fluid levels prove the calcifications arise in calcium
containing fluid as a benign type.
i.) Punctate
calcifications: These are smooth, small, round, and less than 0.5mm in
size with well defined margins. When these forms are not well seen, or
vary in size, they may become "intermediate concern".
Intermediate concern calcifications:
In this group are calcifications which bear forms which can be associated
with both benign and malignant processes. In some cases, more detailed
views may place them into a benign catagory, however if an appreciable
risk of cancer remains, biopsy must be done to exclude cancer.
These are commonly amorphus (without well defined shape) or indistinct.
They may be round or flake shaped, sufficiently small or hazy in
appearence that a more specific morphologic classification cannot be
determined. These characteristics occur early in the development of either
benign and malignant forms before they acheive a charateristic appearence.
Intermediate
concern, a group of poorly defined cacifications, some round, others
irregular with a clustered distribution. These particular calcifications
were benign related to sclerosing adenosis, however similar appearences
are common enough in small cancers to merit biopsy. In looking at serial
mammograms, it can be seen that many benign and malignant calcifications
will pass thru an intermediate phase as they develop more characteristic
morphology.
Calcifications of
High probability of malignancy:
These classes are
often associated with cancer and clearly merit immediate biopsy.
a.) Pleomorphic or heterogeneous calcifications (Granular):
These are usually more conspicuous than amorphic forms, but are neither
characteristic of a benign calcification, nor typically malignant. They
are irregular calcifications of varying size and shape, usually less than
0.5 mm. in size.
Pleomorphic calcifications, on the left grouped irregular calcifications
were found to be benign (fibroadenoma). On the right, irregular
calcifications were associated with ductal carcinoma (cancer).
Close up (magnified) view of heterogeneous granular calcifications of
infiltrating ductal carcinoma.
b.) Fine and/or
branching (casting) calcifications: These are thin, irregular
calcifications that appear linear, but are discontinuous and under 0.5 mm.
in width. Their appearence suggests filling of the l
Section 5:
Evaluation of associated structural changes
Evaluation of
Associated Structural Changes in the breast:
These are changes
that may occur alone or more commonly in the tissues surrounding masses or
calcifications. Many are suspicious in that they imply a process which is
infiltrating and altering the character of adjacent tissues (1-6).
Category 7 - Skin lesion is a benign finding.
1.) Skin retraction:
The skin appears to be pulled or tethered into an abnormality. This is a
common finding in more advanced infiltrative cancers, but can also occur
with scarring due to previous injury or biopsy. In addition to a careful
history to identify any previous injury, previous mammograms can be very
helpful if they demonstrate the skin retraction is a long standing finding
due to scarring, and not a recent result of infiltration.
2.) Nipple
retraction: The nipple is pulled in or inverted. This can be seen as
another sign of advanced cancer infiltration, but is also a fairly common
observation in otherwise normal patients. Previous studies documenting
stability, and the lack of an underlying mass are factors which can reduce
the concern regarding this finding. It is important to exam the underlying
area carefully however to look for architectural distortion which can
indicate a tumor even in the absence of a mass.
3.) Skin thickening:
When diffuse this is often related to other systemic problems. When
localized, it may result from direct infiltration, or tumor blockage of
local lymphatic drainage. As with 1 and 2, the absence of change, and the
absence of an associated mass reduce the importance of this finding.
4.) Trabecular
thickening: This is focal thickening of fibrous septae in the breast. It
raises question of infiltration particularly in association with mass.
5.) Axillary
Adenopathy: Enlarged non-fatty lymph nodes in the axilla may be commented
on. Because the enlargement may be due to inflammatory involvement in the
upper extremity or breast, attributing enlargement to breast malignancy is
often unreliable.
6.) Architectural
Distortion: When disturbance in the course and shape of the normal
trebecular architecture is seen, particularly if it persists with directed
focal compression views, the possibility of infiltration should be
entertained. This is a finding in itself if no mass is seen, and is a
associated finding when distorted or retracted tissues are seen
surrounding a mass or other finding.
7.) Skin Lesion:
This is a mammographic finding projects from skin over breast in two
views. It is almost never associated with breast cancer, but may simulate
a mass. Careful positioning with special tangential views are used to
prove the benign skin location.
Section 6:
Location of lesions in the breast
Location of
Findings:
Every mammographic
finding must be carefully located within the breast to facilitate
correlation physical findings and further evaluations such at mammographic
follow-up or biopsy.
Significant lesions
are triangulated to determine the three dimensional location, using at
least 2 mammographic view. The simplest and most precise localization uses
two orthogonal views (views exactly perpedicular to each other).
The location of the
finding is described in terms of the clinical orientation used in physical
xamination. In this scheme, the breast is viewed as the face of a clock as
the patient faces the examiner. The location is expressed at the position
of the hour hand, such that straight up is 12:00, down is 6:00. The outer
margin of the right breast is 9:00, the outer margin of the left breast is
3:00 and so on. The use of quadrants is an option. Use of both quadrant
and clockface is encouraged. The finding is then localized in the
anterior, middle, or posterior thirds of the breast. Immediately below the
nipple is designated subareolar. It may be helpful to report how many
centimeters the finding is from the nipple.
The clockface
description should be preceded by the side and followed by the depth
Breast Imaging
Reporting and Data System (BI-RADS) Categories
The report system is
designed around a standard format which organizes the presentation of
general and specific mammographic findings. In addition, it categorizes
final assessment and recommendations into six defined categories. Since
each a the six categories carries a specific recommended course of action,
the next step is always clearly articulated between the interpreting
radiologist and the physician coordinating the patients care.
The format is:
1.) Description of
Breast Composition
2.) Description of Finding
3.) Final assessment and Recommendation.
Here is a
description of the contents of the three sections of the standard
report:
1.) Succinct
description of the overall breast composition:
This is an assessment of the amount and distribution of x-ray attenuating
tissues within the breast. As noted in the principles section, the greater
the amount of background tissues, the greater the chance that a tumor may
be
hidden by normal tissues.
Description of
composition uses the following four patterns:
a.) The breast is almost entirely fatty.
b.) There are scattered fibroglandular densities.
c.) The breast tissue is heterogeneously dense, this may lower sensitivity
of mammography.
d.) The breast tissue is extremely dense, which could obscure a lesion on
mammography.
In particular, the
mammographically "dense" breast offers very low
mammographic sensitivity for small masses, and the physical examination
using monthly manual (hands on) examination by the women herself and
yearly
physician examination, assumes greater importance.
There is an ongoing
search for improved imaging techniques to exam the
"dense" breast such as Nuclear Medicine scintomammography and Magnetic
Resonance Imaging, but these techniques are not yet established as
screening
tools.
2.) A clear
description of any significant findings:
For a mass:
size, shape, margins, associated findings and location.
The descriptive
terms used are:
Shape:
Typically benign: round, oval, lobular,
Suspicious: irregular, or architectural distortion.
Margin:
Typically benign: circumscribed, obscured,
Suspicious: indistinct, microlobulated, or spiculated
Density:
High density, equal density (isodense), low density and fat-containing
(radiolucent)
For
calcifications:
size, morphologic description, distribution.
The descriptive
terms used are:
Typically benign: skin, vascular, coarse(popcorn), large rod like, round,
spherical, eggshell, milk of calcium, suture, dystrophic, punctate
Suspicious: indistinct (intermediate suspicion), pleomorphic, fine
branching
(high suspicion).
Distribution:
Typically benign: regional, scattered, or diffuse.
Suspicious: grouped, linear, segmental.
Associated
findings:
Typically benign: skin lesion.
Suspicious: skin retraction, nipple retraction, trabecular thickening,
archtectural distortion, axillary adenopathy,
"Special" Cases:
Typical benign appearence:
Tubular density or solitary dilated duct.
Intramammary lymph node (circumscribed mass with notch or fatty center,
outer quadrant)
Asymmetric breast tissue, Focal asymmetric density
3.) Assessment
Categories
There are 6
categories of assessment and recommendation.
Assessment is incomplete
Category 0: Need Additional Imaging Evaluation
A finding may not be completely seen or defined and will need additional
evaluation including the use of spot compression, magnification views,
special mammographic views, ultrasound, etc. By bringing the patient back
for
additional studies, a firm decision and recommendation can be made.
Category 1: Negative
In this case, there is no appreciable abnormality to report. The breasts
are symmetrical without masses, architectural distortion or suspicious
calcifications
Recommendation: Routine screening mammography.
Category 2: Benign
Finding
This is also a negative mammogram, but the reporting
physician chooses to describe a finding known to be benign such as benign
calcifications, intramammary lymph nodes and calcified fibroadenomas. This
insures
that other individuals viewing the mammogram will not misinterpret a
benign
finding as suspicious, and documents the finding to use in future
mammogram
assessments. Recommendation: Routine screening mammography.
Category 3: Probably
Benign Finding - Short Interval Follow-up Suggested
A finding placed in this category should
have a very high probability of being benign. The finding is not expected
to change over a period of follow-up. Since it is not proven benign, we
wish to establish its stability. Interval
follow-up, usually 6 month intervals for 1 year and yearly follow-up for 2
years can prove benign character
in such lesions, while avoiding unnecessary biopsies. Those lesions that
are cancers will be detected within a reasonably short
period of time by their growth. These cancers will still be small enough
for
an acceptably high cure rate. It is critical to this strategy that
follow-up
be carried out faithfully to avoid incurable growth. Recommendation:
Follow-up in __ months
Category 4:
Suspicious Abnormality-Biopsy Should Be Considered
These findings that do not have characteristic cancer morphology, but have
a
definite substantial probability of being malignant, generally accepted to
be at least 10%, and ideally 30%. The radiologist has sufficient concern
to
recommend biopsy.
Category 5: Highly
Suggestive of Malignancy - Appropriate Action Should Be Taken
These findings are characteristic of cancers and have a high probability
of
malignancy. Biopsy is very strongly recommended.
Previous films: If
the patient has had previous mammograms, it is often possible to
verify that a particular finding has remain unchanged. Since growth is a
reliable characteristic of cancers, the lack of growth (stability) of a
finding over a substantial period of time is a powerful indicator of
benign
nature. If the comparison mammograms are not yet available, a radiologist
may issue an temporary report stating that a final report will be made
when old films are obtained.
It is essential in this case, that comparisons be tracked, and if the
previous mammogram is not found, final recommendations based on the
current
finding be made. The final report must be made within 30 days of the exam.
Wording of Reports:
When available the
present mammogram should be compared to previous
mammograms, and this should be indicated in the report.
Reports should be
organized with a brief description of the breast
COMPOSITION, pertinent FINDINGS, followed by an ASSESSMENT with any
recommendations. The report should be succinct using terminology from the
approved lexicon without embellishment.
Sample Reports:
1. Normal exam
Clinical history:
screening
Comparison exam
dated X/X/XX
The breast are almost entirely fat.
No significant finding is evident.
Impression: Stable
mammogram without radiographic evidence of malignancy.
Yearly mammograms are recommended routine screening.
BI-RADS CATEGORY 1:
Negative
2. Assessment
incomplete
Clinical history:
screening, baseline exam
The breasts are
heterogeneously dense, this may limit the sensitivity of mammography.
In the upper outer quadrant of the right breast in the anterior third
there is a cluster of pleomorphic calcifications.
Impression:
Pleomorphic calcifications in the right breast. Magnification mammmography
is recommended.
The patient will be notified regarding this recommendation and
arrangements will be made for her return.
BI-RADS CATEGORY O:
Needs additional imaging evaluation.
3. Suspicious
abnormality
Clinical history:
Screening, family history of breast cancer
Comparison exam from
General Hospital in Central City dated X/X/XX. There are scattered
fibroglandular densities.
There is a new 2cm spiculated mass in the 8:00 position of the left breast
in the posterior third.
Impression: New
spiculated mass in left breast for which biopsy is recommended. Dr. Smith
was
notified of this finding on X/X/XX. Findings and recommendations were
discussed with the patient
BI-RADS Category 5:
Highly suggestive of malignancy-Appropriate action should be taken
