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Atlas of breast cancer early detection

Breast imaging – Mammography interpretation – Mammography lexicon – Mass


Mass is a finding seen to be persistent in two different mammographic projections and is described by its shape, margins, and density.

The shape of the mass can be described as:
  • round;
  • oval (may include two or three gentle lobulations); or
  • irregular (may have more than two or three gentle lobulations).

Round shape
Round shape is usually suggestive of a benign lesion. However, a well-demarcated cancer, such as intracystic papillary carcinoma, mucinous carcinoma, or medullary carcinoma, may be round in shape. Differential diagnoses include benign proliferative lesion, encapsulated papillary carcinoma , and simple cyst .

Other differential diagnoses include complicated cyst , lymphoma, phyllodes, metastasis ; invasive breast carcinoma , and organised seroma .

Oval shape
Oval shape is usually suggestive of a benign lesion. However, a well-demarcated cancer, such as mucinous carcinoma or metastasis, may be oval in shape. Differential diagnoses include fibroadenoma , fibroadenoma with two smooth lobulations and benign calcification , and medullary carcinoma .

Other differential diagnoses include simple cyst , complicated cyst , intramammary node , invasive breast carcinoma , mucinous carcinoma, phyllodes, lymphoma, and metastasis .

Irregular shape
Irregular shape is suspicious for malignancy . Lesions of irregular shape may also be seen in women with a history of surgery as a result of, for example, scar tissue or seroma collection.

The margins of a mass indicate its demarcation from the adjacent normal breast parenchyma. They may be categorized as:
  • circumscribed,
  • obscured,
  • microlobulated,
  • indistinct, or
  • spiculated.
Note that the features of the margins listed here are for a mass seen in a breast without any history of surgical interventions.

Circumscribed margin
This is more likely a feature of a possible benign mass. Differential diagnoses include fibroadenoma , invasive breast carcinoma , and simple cyst .

Obscured margin
The margin may be obscured because of the superimposition of fibroglandular tissue over the mass. It may be a completely or partially obscured margin. Differential diagnoses include multifocal medullary carcinoma , simple cyst , and invasive breast carcinoma.

Microlobulated margin
A microlobulated margin is suspicious for breast carcinoma . Other differential diagnoses include DCIS or fibrocystic change.

Indistinct margin
An indistinct margin is suspicious for malignancy. Indistinct indicates a lack of clear demarcation from the surrounding breast parenchyma, and leads to the possibility of infiltration. Differential diagnoses include invasive carcinoma , papillary carcinoma , fat necrosis , metaplastic carcinoma , and fibrocystic changes .

Spiculated margin
A spiculated margin is highly suggestive of malignancy. Differential diagnoses include postoperative scar and fat necrosis.

The density of a mass seen on mammography is compared with the adjacent fibroglandular tissue and is categorized as:
  • high density,
  • equal density,
  • low density, or
  • fat-containing.

High density
A lesion of high density is highly suggestive of breast carcinoma .

Equal density
As a stand-alone feature, equal density is inconclusive to differentiate between a benign or malignant mass. The margins of the mass, any calcifications, and axillary nodes need to be seen. Differential diagnoses include fibroadenoma , simple cyst , and intraductal papillary carcinoma .

Low density
Low density is a more likely feature of a benign lesion. Differential diagnoses include benign proliferative lesion , fat necrosis , and hamartoma .


A mass visualized on mammography may be categorized as probable malignant or probable benign based on the combination of various features. A round or oval circumscribed mass of equal or low or fat-containing density is more likely to be a benign mass. An irregular not circumscribed mass of high density is more likely to be malignant mass.


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