Medullary carcinoma of the breast. An unusual cytologic finding in cyst fluid aspirates

Abstract

Cystic medullary carcinoma of the breast is unusual. This report describes five patients with medullary carcinoma who presented clinically with a breast cyst. Fine-needle aspiration biopsy (NAB) was performed as part of the initial physical examination and the retrieved cyst fluid was examined cytologically. Four of the five patients were premenopausal, more typical of benign cystic disease and significantly younger than the average (60+ years) for other forms of cystic breast carcinoma. Only three of the five patients demonstrated suspicious findings of hemorrhagic cyst fluid, a residual mass after NAB, or refilling of the cyst. Due to the relatively young age of most patients, the innocuous clinical presentation, and the abundant inflammatory component noted in the aspiration biopsy cytologic study (ABC), misinterpretation as an inflamed cyst is possible. The ABC of cystic medullary carcinoma is presented with histologic correlation.