Fibroadenoma phyllodes arising in vulvar supernumerary breast tissue: report of two cases.

Ectopic breast tissue, found along the mammary line or sometimes outside it, can exhibit pathologic changes similar to those of the eutopic mammary gland. Fibroadenoma phyllodes, an unusual variant of mammary phyllodes tumor with stromal cellularity similar to a conventional fibroadenoma, rarely arises outside of breast. Its histogenesis is unclear; although some cases suggest an origin in cutaneous adnexa, the presence of normal breast tissue surrounding other tumors favors an ectopic mammary origin. Two cases of fibroadenoma phyllodes arising in ectopic vulvar breast tissue are described.