Breast abnormalities typically discovered by mammogram

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.

Megan Megan
What the hell, Doc. I came to read about asymmetrical tissue, and I think you just said it could be cancer.

Dr. Halls Dr. Halls
Oh oh. I didn’t mean to do that. Read below to feel more reassured.

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.


Just a heads up, this page is getting a little old, but it’s still useful. But there is newer writing at my new page with up to date information on abnormal mammograms.

Asymmetrical breast tissue

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 Pseudo-Angiomatous Stromal Hyperplasia, which is mostly benign.

Asymmetric density

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 quite unlikely, but follow-up imaging is needed, so don’t quit having mammograms. Often, an ultrasound will be performed next, and if ultrasound finds nothing, or finds cysts, that’s good. If ultrasound finds a solid abnormal mass, then a biopsy would be suggested.


Megan Megan
Hold on. Is there a difference between asymmetrical breast tissue and asymmetrical density?

Dr. Halls Dr. Halls
Darn. I guess that is confusing. When the radiologist sees density on the mammogram, he/she might not be able to distinguish between ‘normal breast tissue’ and other things which might be cysts, nodules or even cancer.

Talking Moose
Talking Moose
uncertainty is unavoidable sometimes.

Dr. Halls Dr. Halls
Or sometimes my mind thinks ‘breast tissue’ but my mouth dictates ‘density’ into the report.


Asymmetric breasts

And now for something completely different, nothing to do with cancer. Did you know that it is common for uneven breasts to be asymmetrical, when viewed in a mirror?

Tanya Tanya
Lets say, my left breast is smaller than my right. Suppose you saw a picture of them, and I asked for your opinion?

Dr. Halls Dr. Halls
I’d say, you have beautiful breasts, because I’m a man.

Talking Moose
Talking Moose
You should leave the jokes to me, Doc.


Architectural distortion

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 speculations.

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% of the 4% with architectural distortion, which becomes a very small number.

Billy Billy
You do the math.

Gretchen Gretchen
How long were you waiting to say that? lol, you never do math. It’s 0.05 x 0.04 which gives 0.2%


Clearly, most architectural distortions found on mammography are due to benign causes.

Brittany Brittany
I’m glad you said that. It was giving me anxiety, scared about it.


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.


Mammographically detected breast mass

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.


The word nodule is a term used for a small mass. The word lump refers to something a person feels with their fingers.

Characteristics of mass shape, margin, and density, can suggest malignancy

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.

Lets do a quick Q & A.

  • What about if ultrasound shows a hypoechoic breast mass? It’s basically the same problem, and the approach to the solution involves similar algorithm as a mammographic mass. Look at the margins, shape and size, and decide if it needs a biopsy, and later maybe excision or removal.
  • How often are there no symptoms? Quite often. And conversely, whether or not a lump is palpable or hurts, it doesn’t really change the statistics or the workup.


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.


Benign and malignant indicators for microcalcifications

  Benign/probably benignsuspicious/malignant
MorphologyPopcorn egg shell with a dense centerx (adenofibroma) 
 curvilinear egg shell with a clear center

x (calcified cyst,


 intra and peri-ductal bilateralx (secretory disease) 
 smudgy on CC and fluid level on lateralx (milk of calcium) 
 powderish/BIRADS: amourphous,indistint x
 crushed stone/BIRADS: pleomorphic, heterogeneous x
 casting/BIRADS:linear, branching x
Distributiondiffuse, scatteredx 
 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
 heterogenous x
Size and numbersize in mmx ( >1 )x ( < 0.2 to 1 )
 number per cubic centimetrex ( < 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.

Megan Megan
What percent of microcalcifications are cancerous?

Dr. Halls Dr. Halls
The statistics below are a little confusing, so let me simplify first. About 50% of the time that ‘clustered microcalcifications‘ are present, it turns out to be something needing treatment like DCIS or cancer. But ‘scattered microcalcifications‘ are ignorable.

Megan Megan
So that’s a tip.. look for the word cluster


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 highly 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.

Dr. Halls Dr. Halls
If the mammogram report doesn’t use the words ‘cluster of suspicious microcalcifications‘, the need for a biopsy is unlikely.

Lets to a quick Q and A here:

  • Why do microcalcifications form? When gunk gets stuck in blocked milk ducts, over time it gets hard and binds calcium.
  • How dangerous are microcalcifications? They aren’t the dangerous thing. It’s whatever blocked the ducts. So rephrasing…
  • How dangerous is a cancer with a cluster of microcalcifications? The cancer is judged on its own features, and the microcalcifications have no added danger.
  • How risky are scattered microcalifications? Not.


Interval Changes

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 obscured 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.

Miscellaneous abnormalities

Other findings of note on a screening mammogram might include a finding of inflammatory breast cancer, or possibly diffuse reticular breast density, and also skin thickening.


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