Sclerosing adenosis is associated with distortion of the terminal duct-lobular unit and should be regarded as an aberration of breast involution.

Clinical Features
Patients may present with either a breast lump or breast pain, or may be noted to have an area of increased density or clustered microcalcification on mammographic screening.

Radiology
Mammography
Areas of sclerosing adenosis may be indistinguishable from background parenchyma or show as nonspecific areas of asymmetric density. Sclerosing adenosis may be associated with clustered microcalcification. This is usually fine, granular, powderish calcification that may be indistinguishable from low-grade ductal carcinoma in situ. Definitive diagnosis in such cases can usually be reached with stereotactic core biopsy.

Pathology
Macroscopic Appearance
There are no distinctive macroscopic features.

Microscopic Appearance
Sclerosing adenosis is a disorderly proliferation of lobular epithelial, myoepithelial and stromal cells that leads to an untidy enlargement of the lobule and sometimes to fusion of several involved lobules. The involved lobule or lobules have a crowded cellular appearance. The epithelial acini are usually small and flattened from side to side, with their lumina diminished or obliterated.

The proliferating myoepithelial cells appear plump and eosinophilic and in the early stages fill the spaces between the acini. In older lesions, sclerotic stroma fills the space between the acini. The reduced acinar lumina often contain calcospherites. Apocrine metaplasia may also be present.

Management
If core biopsy is conclusive, no further treatment or follow-up is required.

Where there is an area of doubt, excision biopsy is recommended. Impalpable lesions will require preoperative mammographic localization. There is a mildly elevated risk for the subsequent development of breast cancer (RR 1.6).  This risk is slightly higher in women with a positive family history (RR 2.1).

A.D. Purushotham, P. Britton and L. Bobrow
A prospective study of benign breast disease and the risk of breast cancer. JAMA 2002

References