There are about eight typical kinds of abnormalities revealed with a conventional mammogram. An experienced radiologist is highly tuned to the appearance of abnormalities in breast X-rays, and most of the time has a pretty good idea whether a suspicious abnormality is likely to be malignant or not. Typical mammographic findings from breast cancer screening mammograms would include asymmetrical breast tissue, asymmetric density, architectural distortion, mass, microcalcifications, interval changes compared with previous films, adenopathy, and other miscellaneous findings. Usually, a mammographic abnormality is followed up first by additional imaging studies, such as ultrasound, and if the lesion still appears suspicious it may be sent for biopsy.
Asymmetrical breast tissue is an observation made with respect to the same area on the other breast. It is a fairly vague finding in which there is no focal mass, no distorted architecture, no central density, and no associated breast calcifications. Usually about 3% of breast screening mammograms will show asymetrical breast tissue. Only a very small percentage of women with asymmetrical breast tissue will actually be sent for a biopsy, and typically only a very small percentage of these will ultimately be diagnosed as breast cancer. Asymmetrical breast density should really only be viewed as a concern when it is also associated with a clinically palpable breast asymmetry. Otherwise, a certain amount of asymmetrical breast tissue should be considered a normal variation which occurs in some women. In some cases, the asymmetrical breast density can be attributed to pseudoangiomatous stromal hyperplasia, which is mostly benign.
An asymmetric density in terms of the first mammographic finding usually refers to an 'opacity' (obscured view in part of the breast) which is visible on only one projection (or one 'view or angle' of the X-ray). Typically, additional views from other X-ray angles are requested as an immediate follow up. Asymmetric densities can be the result of benign causes such as post surgical scarring, breast cysts, fibrosis and sclerosing adenosis, or even focal fibroglandular tissue growth which may have developed as a result of hormone supplementation. But, an asymmetric density could also be caused by ductal or lobular breast carcinoma. In the absence of an actual 'mass', breast cancer is less likely, but follow-up imaging and probably biopsy are warranted.
An architectural distortions on a mammogram is basically a disruption of the normal 'random' pattern of curvilinear and fine linear radiopaque structures normally seen on a breast X-ray. There is no visible mass, but the distortion often appears as a 'stellate' shape or with radiating spiculations.
Patients who had architectural distortion on mammography were more likely to have positive margins than patients with masses or calcifications. This may be because architectural distortion on mammography is most commonly due to benign conditions, causing the surgeon to excise with minimal margins. Tumors presenting as architectural distortions on mammography were also significantly larger than tumors presenting with other mammographic abnormalities. Patients undergoing biopsy for nonpalpable architectural distortions should be excised more widely to reduce the risk of positive margins. It may be estimated that around 4% of women who undertake a screening mammogram present with an architectural distortion. The number of those women in which the architectural distortion would actually represent invasive breast cancer is very low, perhaps 5%-7%. Clearly, most architectural distortions found on mammography are due to benign causes. As a result, most biopsies of suspicious architectural distortions tend to be a little bit on the small side. But in the event it did represent invasive breast cancer, it would be important to excise the lesion with wider margins.
Architectural distortions often are an accompanying feature of breast cancer masses as well. Almost 80% of mammographically detected breast masses which also have architectural distortions turn out to be invasive breast cancers.
At a certain point, the radiologist interpreting the mammogram would be inclined to call a suspicious feature an actual 'mass'. A mass is a 'space-occupying' lesion seen on at least two projections or 'viewpoints'(CC, MLO), and most mammographically detected breast masses tend to have curved, convex borders. The mass itself is typically then described according to three features; the shape or contour, the margin, and the density. The mammographic image below shows a small nodule with suspicious indistinct margins, possibly invasive ductal carcinoma. (A nodule is a term used sometimes for a small, I'll-defined mass )
In terms of shape, if it is round, oval, or slightly lobular, the mass is probably benign. If the mass has a multi-lobular contour, or an irregular shape, then it is suggestive of malignancy. 'Margin' refers to the characteristics of the border of the mass image. When the margin is circumscribed and well-defined the mass is probably benign. If the margin is obscured more than 75% by adjacent tissue, it is moderately suspcicious of malignancy. Likewise, there is moderate suspicion if the margin is microlobulated ( i.e. having many small lobes ). If the margin is indistinct or spiculated ( consisting of many small 'needle-like' sections) then there is also high suspicion of malignancy.
'Density' is usually classified as either fatty, low, iso-dense, or high. The mass is probably benign for fatty and low densities, moderately suspicious of malignancy for an iso-density, and highly suspicious of malignancy at high densities. The mammographic characteristics of breast masses is quite a complex and detailed study.
Microcalcifications are on of the main ways breast cancer is mammographically detected when it is in the very early stages.(DCIS) Microcalcifications are actually tiny specks of mineral deposits (such as calcium) They can be distributed in various ways. Sometimes microcalcifications are found scattered throughout the breast tissue, and they often occur in clusters. Most of the time, microcalcification deposits are due to benign causes. However, certain features and presentations of microcalcifications are more likely to be associated with malignant breast cancer.
|Morphology||Popcorn egg shell with a dense center||x (adenofibroma)|
|curvilinear egg shell with a clear center||
x (calcified cyst,
|intra and peri-ductal bilateral||x (secretory disease)|
|smudgy on CC and fluid level on lateral||x (milk of calcium)|
|crushed stone/BIRADS: pleomorphic, heterogeneous||x|
|segmental/within a major system, wedge shaped, nipple oriented||x|
|clustered/usually grouped in less than 2 cubic centimetres||x|
|linear, branching within the galactophores||x|
|Size and number||size in mm||x ( >1 )||x ( < 0.2 to 1 )|
|number per cubic centimetre||x ( < 3.5 )||x ( > 3-5 )|
When microcalcifications are encountered on a mammogram, knowing that DCIS is common, the chances are good that it could be DCIS and less likely to be invasive cancer. It all depends on what the actual microcalcifications look like and how extensive they are.
If the microcalcifications are 'Powderish', with either a fine, indescernible, or 'cotton ball' appearance, then the probability of DCIS is about 47%, and most frequently results in a 'low-grade' cancer. When the microcalcifications have the 'Crushed Stone' characteristic, appearing either as coarse, granular, angular, broken-needle-tip, arrowhead, or a spearhead shape, then the probability of DCIS is about 61%, the breast cancer classified as low to intermediate-grade. But if the microcalcifications have a 'Casting' appearance, then the probability of DCIS is about 96%, the breast cancer classified as high-grade.
Casting microcalcifications typically appear in two variations. Variant A is called 'dense casting, with linear and branched, fragmented, or irregular features. Variant B is called 'dotted casting', with granular and branched, dotted, or snakeskin-like features.
Note, while DCIS is generally considered a milder breast abnormality, it must be stressed that not all kinds of DCIS with microcalcifications are equally curable. There is a new line of scientific evidence which identifies a highly aggressive-invasive subtype of casting microcalcification in the micropapillary DCIS subtype, which has a poor prognosis and should be treated with mastectomy. The relative ratio between the carbonate content and the protein matrix within the microcalcification may also have some relationship to the type of grade of ductal carcinoma associated with them.
An 'interval change' is simply a notable difference on a second or third scan as compared to a previous scan. Typically there may be changes in size, density and contour of the mass, or changes in size, number, configuration and pattern or microcalcifications. A change in the density or contour of a mass is a fairly definite sign of malignancy, but changes in the pattern of microcalcifications is thought to be a less reliable indicator of malignancy. Interval change might be one area where a computer aided detection system can assist in breast cancer identification, but an experienced radiologist is sure to be suspicious of any interval changes on mammograms. (The 'screening interval' is the recommended amount of time between ongoing breast cancer screenings, usually 1 to 2 years.)
Adenopathy refers to a finding of enlarged lymph glands, and a very small percentage of women undergoing a breast cancer screening mammogram will present with these features. (In some cases the mammogram detects enlarge axillary lymph glands, but no breast mass. Sometimes the cause in an 'occult' primary breast cancer, either obscurred from view or newly developed in a different region of the breast, or in the other breast.) An axillary lymph node that seems enlarged on a mammogram could contain cancer, but some lymph nodes can normally be quite large anyway. However, mammographical features of benign and malignant lymphadenopathy are quite often indistinguishable. Sometimes the presence of intranodal calcifications can be more suggestive of malignancy as well.
As a rule of thumb, an axillary lymph node is suspicious if its size is greater than 2 cm and with no fatty hilum. More precicely, when a lymph node has a fatty hilum visible, the outer cortex should be 5 millimeters thick at most, and usually less. When the cortex is 6mm or thicker, chances of cancer spread into the lymph node are significant. If there is no fatty hilum visible, then the entire lymph node measured across its smallest short-axis width, should be no larger than 10 millimeters.
Ultrasound is often used as a follow-up when enlarged lymph glands are detected. Some of these will be referred for either a fine needle or excisional biopsy. Sometimes a suspected enlarged lymph node turns out to be either a lipoma, fibroadenoma, or a haematoma. Common benign causes of benign lymphadenopathy might also include reactive nodal hyperplasia, or collagen vascular disease. An acute bacterial infection or tuberculosis might also bring about the condition. If the lymphadenopathy is actually caused by a malignant carcinoma, it is often associated with breast cancer development in the previously unaffected breast.
Other findings of note on a breast cancer screening mammogram might include a finding of inflammatory breast cancer, or possibly diffuse reticular breast density , and also skin thickening.
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