Mammogram shows Mass: Characteristics of a Mass
All about Mammograms
A mammogram is an X-ray of the breast. If anything curious shows on mammogram, usually appearing as a ‘shadow‘ of some kind, the next step is probably an ultrasound. Medics will also perform a careful clinical exam.
Your radiologist may request a breast biopsy at the mammogram stage. However, sometimes a radiologist will delay the request for a biopsy until ultrasound confirms a mass. Also, specialists may request a breast biopsy if the mammogram shows mass and the palpable features are suggestive of a mass.
Next Step after Mammogram shows Mass
So, there are typical steps that radiologists usually recommend when a mammogram shows a possible ‘mass’. The radiologist might arrange for magnified mammogram views to look for microcalcifications.
Alternatively the radiologist might arrange for a breast ultrasound to see if ‘the mass’ is actually a cyst, and not a solid mass. Furthermore, If multiple ‘masses’ or solid nodules are present, this increases the chances that there is not a cancer.
If cysts are present on mammogram, they are definitely not cancer.
If the radiologist think the mass may be solid, because of the shape and the ultrasound results, then it might need a biopsy.
The breast mammogram in the image, certainly appears to have a nodule of some sort, but since it may or may not be a real nodule, one could label it as an ‘asymmetric density’ or a ‘developing asymmetry’.
When a mass shows up on one mammogram view, the radiologists will ask himself, ‘is it only one view’?’ If so, it may be ‘asymmetric density’. The radiologist must look at both views, (They call them ‘orthogonal’ views. Orthogonal views are views from different angles, usually at 90 degrees, like looking at a face from the front and side )
Radiologist consider a mass seen in both orthogonal views to be a ‘true’ mass.
Mammogram shows Mass: Distortion and Asymmetrical Breast Tissue
Other curious findings which lead to a speculation of ‘unconfirmed mass’ include asymmetrical breast tissue, and architectural distortion. So, your radiologist will order more tests to confirm these uncertainties.
Ultrasound is usually used, along with physical exam, to confirm an actual mass. If there is no confirmed mass, it might be called a ‘pseudo-mass‘,or a ‘composite shadow from overlapping structures’, and no further evaluation is necessary.
If there is a mass, your radiologist will usually perform additional mammogram views and an ultrasound. However, if a mass appears unlikely to be cancer, your radiologist will suggest follow-up imaging in 6 months.
What does it mean if you have a ‘cyst’?
A cyst is a ‘fluid-filled‘ cavity of some kind.
Breast cysts are very common and pose no risk for cancer whatsoever. A cyst is like a water balloon, meaning fluid on the inside and a thin membrane around the outside.
On a mammogram, a cyst looks like a round blob, but a round shape could be a tumor too. The smooth, round shape of a cyst wall gives a hint on the mammogram, but ultrasound is necessary to confirm it is just a cyst.
Sometimes there are suspended particles in the fluid, and these appear as ‘echoes‘ on the ultrasound. This creates a bit of uncertainty as to whether or not it is ‘just fluid’, because these echoes can make it appear as solid.
A screening finding of a simple cyst
If your mammogram shows mass, a simple cyst is the most common pseudo-mass found at screening. Breast cysts tend to affect women in the 30 to 50 age range, and are uncommon in post menopausal women.
Cysts often form in the lobule from a distended acini. Most breast cysts are the result of fibroadenoma or breast fibrocystic disease, which are completely benign.
On a mammogram a cyst is typically round or oval and with a well circumscribed margin. Indeed, cysts can appear alone or in small groups. Sometimes, over time, cysts may disappear or change in size.
Simple breast cysts may also show rim-like calcifications. On the ultrasound a cyst will be anechoic featuring smooth, well defined walls. Ultrasounds are up to 100% accurate in determining simple breast cysts, unless there are particles of some kind floating in the fluid. A simple cyst is considered BIRADS category 2.
Mammogram shows Mass: Clustered Microcysts and Complicated Cyst
Floating particles in a cyst are formally referred to as ‘clustered microcysts’. On the ultrasound these cysts will appear as very small anechocic dots, each smaller than 2-3 mm, with no discrete solid components.
These tiny foci have very thin septations between them ( less than 0.5 mm). The radiologist will be looking to differentiate potentially complicated cysts from apocrine metaplasia, or other more common fibrocystic changes.
A ‘complicated’ cyst is a curious term based on the ‘complicated‘ ultrasound appearance. What makes it complicated is that something besides pus or blood may be responsible for the small echoes on the ultrasound. The cause of the echoes could be increased fluid levels, floating debris, or swirling echogenic foci (particles). Aspirated fluid samples will typically appear green, yellow, or milky-clear.
A complicated cyst will not appear to have a thickened wall or any solid mural nodules.
Complicated cysts and clustered microcysts are considered ‘probably benign’ if they are non palpable. That would correspond to a “BIRADS category 3, and given short term follow-up.
However, if the lesions are palpable a breast cancer surgeon will probably aspirate (drain with a needle), and order a biopsy too.
Palpable complicated cysts and clustered microcysts are considered BIRADS category 4.
Mass on Mammogram: Complex cystic mass
Sometimes the differences between cystic lesions are subtle and vague. Quite recently, the term ‘complicated’ cystic mass and ‘complex’ cystic mass, were separated, even though semantically they mean just about the same thing.
A ‘complex’ cystic mass is one that contains both fluid components AND solid components. These solid features could present as either a thickened lesion wall, or as solid mural nodules.
Whether palpable or not, all complex cystic masses will require biopsy to figure out what is going on. A complex cystic mass corresponds to BIRADS category 4 or 5.
Mass on Mammogram: Asymmetric Density
An asymmetric density means that some sort of ‘opacity’ (shadow– or something making it more difficult for light to pass through ) is visible, but only on one projection.
Additional projections from other angles attempt to confirm that the shadow was not just incidental. Sometimes the opacity is seen on two views, but lacks the convex-outward borders that are typical of a true mass, and this situation is still termed ‘asymmetric density.’
Ultrasound is also a useful tool for a follow-up evaluation, as well as ‘spot compression’ X-rays. Note that all mammograms are done with some breast compression, but a spot compression test uses a special plate or cone which lets you see a clearer image of a much smaller area. Margins also become clearer using spot compression.
Global Asymmetry, Focal Asymmetry, Developing Asymmetry
When there is asymmetric density on a mammogram image, it can mean that a mass is developing, but it is far more likely that it is something else.
There are different types of asymmetry; global, focal, and developing, and the chances of malignancy, though low, tend to increase if there are new developments from previous mammograms, and if the lesion is, or becomes, palpable.
Global asymmetry
means that the area of density includes a significantly large portion of the breast. In most cases this is the result of normal variations in hormone levels.
However, if something is palpable, the possibility for malignancy is as high as 10%, and the lesion will require further evaluation. Now, if the lesion appears to be a solid mass, or has suspicious microcalcifications, or an architectural distortion, then a biopsy will be necessary.
Focal asymmetry
Means the suspect asymmetry-mass is much smaller, and has a similar shape on two views. It lacks the clear borders that we see in a true mass, and it usually appears as an ‘island’ of normal , yet dense fibroglandular tissue. The likelihood of malignancy with focal asymmetry is less than 1%.
Follow-up procedures will, to some degree, depend upon whether or not this is a first or subsequent screening. If there are previous mammograms and the focal asymmetry seems to be stable, then a radiologist will consider this mass to be benign. However, yearly screenings may be necessary for monitoring purposes.
If this is the first screening and without other worrisome features, the lesion is ‘probably benign‘ or about a BIRADS category 3, radiologists recommend short term ( 6 months or less ) follow-up. However, the chance of malignancy is still less than 2%.
Developing Asymmetry
A developing asymmetry is a focal asymmetry which is new, more dense, or larger than on a previous mammogram. The likelihood of malignancy is quite high, between 10% to 15%.
With developing asymmetry, a raiologist will always require additional evaluations. A biopsy will likely be necessary if the lesion now seems ‘indeterminate’ in comparison to previous screenings.
A surgeon will always perform a biopsy if there are suspicious microcalcifications, evidence of a solid mass, or architectural distortion.
Differential Diagnosis for a solitary, well-circumscribed mass
A mass suspicious of breast cancer is a ‘space-occupying’ lesion seen on at least two mammogram projections. Furthermore, cancerous tumors also tend to be more dense in the middle than at the edges.
Radiologists tend to describe breast masses according to their shape, margin, and density. ‘Density’ more or less refers to the amount of fat tissue in the mass in comparison to the surrounding breast tissues.
So, when deciding whether or not the mass is likely to be breast cancer, the screening physicians must consider a differential diagnosis for a number of common ailments.
For relatively non-fatty masses: Cyst, fibroadenoma, solitary intraductal papilloma, dermal lesion, hematoma, abscess, phyllodes tumor, circumscribed malignancy.
For relatively ‘fatty’ masses: lymph node, cytosteatonecrosis (or fat necrosis), lipoma, hamartoma, galactocele.
Ultrasound differentiation of a benign versus malignant solid mass
Specialists will consider a mass ‘malignant’ (until proven otherwise) when it contains any single malignant feature found on ultrasound.
Mammogram shows Mass: Malignant Features
These features include:-
- Angular margins
- Spiculations
- Shadowing
- Branch pattern extensions
- Certain microcalcifications
- Duct extensions
- Microlobulations
- Markedly hypoechoic
- Parietal thickening
- Intracystic nodules
- Size greater than 1 cm
- Growth non-parallel to the skin.
Mammogram shows Mass: Benign Features
Radiologists will consider a mass benign, until proven otherwise, if it has no malignant features. Plus:-
- Few lobulations
- Ellipsoid shap
- Intense uniform hyperechogenicity
- Thin Echogenic capsule
Furthermore, radiologists will call a breast mass ‘indeterminate’ if there are no malignant features and none of the benign combinations.
In the ultrasound image below, one notes a suspicious hypoechoic mass with microlobulations. This mass would definitely need a biopsy. A radiologist would probably give a BI-RADS classification of either category 4C, or 5. ( Many constituencies don’t use BI-RADS 4 a, b, and c, but simply differentiate between categories 4 and 5. If required to choose, this mass is most likely a BI-RADS category 5 breast lesion.)
BI-RADS categories of suspected masses: Probability of malignancy and usual follow up
The BI-RADS categories are based on various mass characteristics and indicate increasing probabilities of malignant breast cancer.
Radiologists usually would recommend a biopsy at BI-RADS category level 4. The chances of malignancy greatly increase once features consistent with the ‘intermediate’ level of BI-RADS 4b are present.
These features include powderish microcalcifications along with microlobulated contours and evolving asymmetric densities.
| BI-RADS category | Screening Findings | Approximate probability of malignancy | Follow-up Recommendation |
| 0 | Evaluation incomplete, needs additional imaging | ||
| 1 | Negative | 0 | mammogram at normal interval |
| 2 | Benign | 0 | mammogram at normal interval |
| 3 | Probably Benign | less than 2% | shortened interval mammogram |
| 4 | Suspicious abnormalities | Ranges from 3 to 95% | Consider a biopsy |
| 4a | Suspicious abnormalities | 3-10% | biopsy |
| 4b | Suspicious abnormalities | 10-50% | biopsy |
| 4c | Suspicious abnormalities | 50-95% | biopsy |
| 5 | Highly Suggestive of Malignancy | 95% or more | Appropriate confirmation and staging procedures |
| 6 | Malignancy proven histologically | 100% | Staging procedures and treatment therapies |
References
- American College of Radiology. Breast Imaging and Reporting Data System. Fifth edition. Reston V A, American College of Radiology 2004
- Leung JW, Sickles EA. (2007) Developing asymmetry identified on mammography: correlation with imaging outcome and pathologic findings. AJR Am J Roentgenol 2007;188:667-675. https://www.ncbi.nlm.nih.gov/pubmed/17312052
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