Masses are three-dimensional lesions which may represent a localizing sign of breast cancer. They are described by their location, size, shape, margin characteristics, x-ray attenuation (radiodensity), effect on surrounding tissue, and any other associated findings (i.e. architectural distortion, associated calcifications, skin changes). Depending on the morphologic criteria of the mass, the likelihood of malignancy can be established.

Location

The location of the mass may be established from the physical examination if the mass is palpable. Otherwise, its location can be determined from several different mammographic views. It is important to realize that the mass seen on a mammogram may not correspond to a palpable lump. Because breast cancer tends to develop in the peripheral zone of the breast's parenchymal cone, a mass' location can raise suspicion of malignancy.

Size

Size alone does not predict malignancy. Nonetheless, the size of a malignant mass is indicative of its progression. Needless to say, the objective of mammography is to detect breast cancer in its earliest stage of development.

Shape

A mass shape may have one of five characteristics: Round, Oval, Lobular, Irregular, and Architectural distortion. The descriptions are fairly self-explanatory, and a schematic picture of each shape is shown below. Architectural distortion is not technically a mass since there is no definite mass visible. It can be identified by distortion in the normal breast architecture, including spiculations radiating from a point and focal retraction or distortion of the parenchyma edge. Architectural distortion can also be an associated finding of a mass.

Margins

The margin is the border of a mass, and it should be examined carefully, sometimes using magnification view for clarity. It is one of the most important criteria in determining whether the mass is likely to be benign or malignant. There are five type of margins as defined by BIRADS: Circumscribed, Obscured, Micro-lobulated, Ill-defined, and Spiculated. Circumscribed margins are well defined and sharply demarcated with an abrupt transition between the lesion and the surrounding tissue. Microlobulated margins have small undulating circles along the edge of the mass. Obscured margins are hidden by superimposed or adjacent normal tissue. Ill-defined margins are poorly defined and scattered. Spiculated margins are marked by radiating thin lines. If there is no visible mass, the basic description of architectural distortion with spiculation as a modifier is used.

X-ray attenuation

X-ray attenuation is a description of the density of the mass. Generally speaking, breast cancer often appears denser (whiter) than the surrounding normal breast parenchyma.

Effect on Surrounding Tissue and Associated Findings

These are descriptions associated with the mass such as architectural distortion, enlarged duct, skin changes, nipple and areolar abnormalities, etc.