Proliferation of epithelial cells lining the terminal duct-lobular unit is known as epithelial hyperplasia. The degree of hyperplasia can be graded as mild, moderate or florid. There may be associated atypical features. The significance of atypia is related to the risk of subsequent development of breast cancer. There is a strong interaction with family history and atypical hyperplasia.
Three case control studies have demonstrated a relative risk for breast cancer ranging from 3.7-13 in patients with atypical hyperplasia.
Patients with atypical hyperplasia do not present with classical clinical features. They can present with a lump or lumpiness or may be noted to have an abnormality on screening mammography.
There are no specific mammographic features associated with hyperplasia, and the most common way to diagnose mammographically is in association with a cluster of microcalcification.
Epithelial hyperplasia of usual type can occur in any part of the breast glandular structure but predominantly affects the terminal duct-lobular unit.
Depending on the number of cell layers present, the degree of duct expansion and the presence of secondary lumina, these proliferations can be subdivided into mild, moderate and florid. The cytological inter-relationships of usual-type hyperplasia are haphazard, giving an untidy appearance with irregular and often slit-like secondary lumina where these are present. The cells themselves have regular nuclear chromatin and vary in shape from spindle and elongated to round. An admixture of myoepithelial cells is usually present.
Atypical ductal hyperplasia (ADH) is intermediate between florid epithelial hyperplasia and low-grade ductal carcinoma in situ (DCIS) usually of cribriform type. Thus, at the lower end of the spectrum, ADH includes features of florid epithelial hyperplasia plus small focal areas of more uniform cytology and more even placement of cells. The atypical features give rise to the more rounded, very regular outlines of the secondary lumina characteristic of low-grade DCIS. The cells in ADH also show more nuclear hyperchromasia than those in usual-type epithelial hyperplasia. The distinction of ADH from low-grade DCIS can be extremely difficult and is based on the degree and extent of the atypical features.
Atypical lobular hyperplasia (ALH) is a uniform proliferation of small, monomorphic cells that partially fill most of the acini in one or more lobular units. Some, but not all, of the acinar lumina are obliterated.
Following a pathological diagnosis, the decision to follow up a patient should be based on subsequent risk for breast cancer. Patients with atypical hyperplasia may be considered for entry into breast cancer prevention trials.
A.D. Purushotham, P. Britton and L. Bobrow
A prospective study of benign breast disease and the risk of breast cancer. JAMA 2002