Fibroepithelioma-like changes occurring in perianal Paget's disease with rectal mucinous carcinoma: case report and review of 49 cases of extramammary Paget's disease

Background: Anogenital Paget's disease (PD) may be accompanied by varying degrees of epidermal hyperplasia. The histological changes can be reminiscent of fibroepithelioma of Pinkus. Methods: We present a case of perianal PD associated with fibroepitheliomatous epidermal hyperplasia in a 76-year-old-man with an underlying rectal mucinous carcinoma. We also carried out a retrospective analysis of 51 biopsies from 49 cases of extramammary PD to see whether particular epidermal changes occur in association with PD in different anatomic locations. Results: A tumor, 3 cm in diameter, was noted in the patient's perianal skin. Histologically, it was composed of anastomosing thin epithelial strands with follicular differentiation. Paget's cells were distributed in the epithelial strands of this tumor as well as in the surrounding epidermis and anal epithelia. In our series of extramammary PD, epidermis was hyperplastic in two of two perianal cases, 26 of 43 genital skin samples, and one of six axillary PD biopsies. The stroma beneath the hyperplastic epidermis tended to be rich in thin collagen fibers and fibroblasts. Conclusions: Anogenital PD was more frequently associated with epidermal hyperplasia than axillary PD. Fibroepitheliomatous hyperplasia may be induced by the altered stroma associated with PD.