A 37-year-old female with no significant family history of malignancy presents with asymmetric enlargement of the left breast, palpable on physical examination.


Mammographic CC and MLO views demonstrate a large, round, well-circumscribed mass in the lower outer quadrant of the left breast with mixtures of prominent fat and fibroglandular tissue elements. A pseudocapsule is present, representative of a rim of compressed surrounding parenchyma. The mass assumes a “breast-within-a-breast” appearance, compatible with a hamartoma. Sonographic images show sonolucent fat and echogenic glandular elements without suspicious features. MR images show nonspecific collection of glandular tissue interposed between variable heterogenous increased signal on T1W sequences, which drops out on fat saturated sequences, indicative of fat. Mass enhances comparably to that of background breast tissue.


Mammary hamartoma, or fibroadenolipoma, is a focal developmental, benign malformation, falling into category 2 of BI-RADS. Mammographic findings, as discussed above, are diagnostic and no further evaluation is warranted.

Microscopic features are nonspecific and demonstrate fat mixed in varying proportions with mammary parenchyma. Lobules and ducts are normal without cytologic atypia. Malignancy may arise within the contained tissue elements in the form of invasive ductal and/or lobular ductal carcinoma in situ, although this is extremely rare.

Hamartomas represent about 4 percent of all breast tumors. These lesions are usually asymptomatic but may present as a vague soft breast mass or thickening. When palpable, the mass is painless. Hamartomas occur solely in females, presenting at any age (mean: 45 years). There is no genetic predisposition or inheritance pattern. No treatment is necessary unless there are atypical features (e.g., suspicious calcifications or intrinsic mass).

Tse GMK, et al. Hamartoma of the breast: a clinicopathological review. 

Mammography

37-year-old female with no significant family history of malignancy presents with asymmetric enlargement of the left breast, palpable on physical examination.

Image IQ: 37-year-old Female with Markedly Asymmetric Breasts