Microglandular adenosis. A benign lesion simulating invasive mammary carcinoma.

Microglandular adenosis (MGA) is a benign mammary disease in which small uniform acinar structures seem to grow haphazardly in the mammary parenchyma. While most often an inconspicuous microscopic lesion, MGA can cause a palpable tumor. This report is based on a review of 13 patients who presented with palpable tumors which were composed in part or entirely of MGA. The mean age was 53 years. In two cases, the mass was painful; a third patient described changes in the size of the tumor with menstrual cycles. Four patients had carcinoma associated with MGA. Two women had MGA coexistent with in situ lobular and intraductal carcinoma, respectively, when the carcinoma was diagnosed. Two other patients developed invasive carcinoma at intervals of 6 and 18 years subsequent to a biopsy of MGA. Both patients had hyperplastic foci in the MGA prior to developing carcinoma. These findings suggest that complete excision of MGA is appropriate and that it is prudent for patients with MGA to seek regular clinical follow-up.