Extramammary Paget's disease most commonly occurs on the female external genitalia and rarely occurs in the perianal region and male external genitalia. We present the clinical and pathologic features of 5 cases of perianal Paget's disease and review the literature.
Clinical and pathologic data were recorded for 5 cases of perianal Paget's disease. Cases were studied retrospectively with special stains, including periodic acid-Schiff, mucicarmine, Alcian blue, carcinoembryonic antigen, S100 protein, pan-keratin, gross cystic disease fluid protein-15 (GCDFP-15), lysozyme, CD15 (Leu-M1), cytokeratin 7 (CK7), and cytokeratin 20 (CK20).
Three (60%) of 5 patients had concurrent rectal adenocarcinomas. All cases reacted positively for pankeratin, although the intensity and distribution of staining varied. Both cases not associated with an underlying carcinoma showed strong GCDFP-15 and CK7 expression and an absence of CK20 expression. The 3 cases associated with an underlying malignancy demonstrated CK7 and CK20 expression and an absence of GCDFP-15 expression. All cases were negative for lysozyme and CD15 (Leu-M1).
The 5 cases reported herein demonstrate that perianal Paget's disease is a heterogeneous entity. The high frequency of associated underlying malignancies and resultant poor clinical outcomes highlight the importance of an aggressive search for a second malignancy. In some cases, perianal Paget's disease merely represents a cutaneous manifestation of an underlying rectal adenocarcinoma and demonstrates a CK7+/CK20+/GCDFP-15-/lysozyme-/Leu-M1- immunophenotype and signet ring Paget's cells. Other cases represent primary adenocarcinomas of the skin, which are associated with a CK7+/CK20-/GCDFP-15+/lysozyme /Leu-M1- immunophenotype and an excellent prognosis if adequately resected. Immunohistochemical studies, particularly CK20 and GCDFP-15, are useful adjuncts in distinguishing primary and secondary perianal Paget's disease.