Papillary transitional cell carcinoma of the breast: a report of five cases with distinction from eccrine acrospiroma.

Papillary carcinomas of the female breast exhibit a spectrum of morphologic appearances and might be mistaken for benign intraductal papillary lesions or papillary adnexal neoplasms. We report herein five cases of papillary carcinoma in which the epithelium closely resembled transitional cells of the urinary bladder. Grossly, the tumors had a nodular or papillary appearance, white, tan, or red in color. The microscopic features were those of an intraductal papillary proliferation of solid layers of epithelial cells overlying fibrovascular cores. The proliferating cells assumed a whorled or streaming growth pattern, with flattening of superficial cells. One case showed microinvasion. Comparison with a similar number of cases of the solid variant of papillary carcinoma of the breast showed a greater range of nuclear pleomorphism, mitotic counts, and a more varied immunohistochemical profile in the papillary carcinomas with transitional cell features. Eight cases of eccrine acrospiroma occurring in the female breast also displayed a solid or solid papillary pattern, with flattened superficial cells. These occurred in a younger age group, were located in the dermis or subcutis, and usually had zones of clear cells visible at low magnification. No evidence of recurrent or metastatic disease was found in the four patients for whom follow-up was available; the length of follow-up ranged from 18 months to 11 years. The stimulus for the development of this unusual phenotype is unclear, but the transitional-like variant seems to behave in a fashion similar to that of other types of papillary carcinoma of the breast. Distinction of this malignant lesion from various benign lesions that occur in the same region is mandatory.