Fibromatosis of the breast: a case report.

We report a case of fibromatosis clinically suggestive of breast cancer, in which cancer treatment was prevented by fine needle aspiration (FNA) cytology. The patient was a 46-year-old Japanese woman who presented with nipple retraction of the left breast. Mammography demonstrated thickened nipple skin and an ill-defined, fairly dense tumor retracting the nipple. Ultrasonography showed an irregular hypoechoic tumor with a thick boundary echo and back echo attenuation. FNA was performed, and the aspirates consisted of isolated pleomorphic spindle cells showing large nuclei with fine chromatin and lacy cytoplasm, and papillary epithelial and myoepithelial cells. Thus an epithelial malignant tumor was ruled out. In this case, in which carcinoma was clinically strongly suspected and in which aspirates consisted of isolated pleomorphic spindle cells, fibromatosis should be considered to avoid unnecessary radical surgery.