Fine-needle aspiration cytology of mammary fibromatosis: report of two cases.

The purpose of this study is to evaluate cytologically two cases of mammary fibromatosis (MF). Prior to FNAC, clinical and mammographic suspicion of carcinoma and fibroadenoma were present. In both cases cytology disclosed the presence of numerous spindle cells admixed with epithelial cells. In the first case, carcinoma was excluded and the diagnosis of "spindle-cell proliferative lesion" was established. The second case was erroneously diagnosed as "cellular fibroadenoma" due to the presence of monolayered ductal epithelial groups and stromal tissue. In both cases local excision of the lesion was recommended. Although in a strict sense fibromatosis is a pure stromal lesion, the frequent presence of epithelial groups in the smears should raise a differential diagnosis with other more frequent mixed (epithelial and stromal) lesions such as fibroadenoma, cystosarcoma phyllodes, and metaplastic carcinoma. Due to the fact that clinically and mamographically MF is frequently confused with malignancy, preoperative recognition is essential since in many cases it would avoid unnecessary radical surgery. In this sense cytology offers very important preoperative information.