Perianal Paget's disease: distinguishing primary and secondary lesions using immunohistochemical studies including gross cystic disease fluid protein-15 and cytokeratin 20 expression.

Abstract

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.