Perianal Paget's disease: a histologic and immunohistochemical study of 11 cases with and without associated rectal adenocarcinoma.

Perianal Paget's disease is rare, and its relationship to an associated internal regional cancer has been ill defined. We analyzed the histologic and immunohistochemical features of perianal Paget's disease in 11 patients to determine the frequency and relationship of associated regional internal carcinoma and to gain insight into its histogenesis. Of five patients with documented rectal adenocarcinoma, it was discovered synchronously with the Paget's disease in four and, subsequently, in one. Paget's cells of signet ring type predominated in four cases. Intraepithelial glands with intraluminal dirty necrosis were present in four cases. The immunophenotype in four cases studied was cytokeratin (CK)7+/CK20+/gross cystic disease fluid protein- (GCDFP) in both the intraepithelial Paget's cells and the invasive rectal adenocarcinoma. Six patients did not have documented rectal carcinoma. The Paget's cells in four were CK7+/CK20-/GCDFP15+. Three of these had purely intraepithelial Paget's disease, and invasive or metastatic disease developed in none after wide local excision. Bilateral inguinal lymph node metastases developed in the fourth patient, and the patient died 8 months after diagnosis of Paget's disease. In two patients, the Paget's cells were CK7+/CK20+/GCDFP15-. Recurrent intraepithelial perianal Paget's disease developed in one patient at 7 months; the patient was alive without disease at 24 months, and the other patient had several intraepithelial recurrences of perianal Paget's disease, and, subsequently, a large perianal tumor of uncertain cell type developed at 108 months, which led to the patient's death. We conclude that there are two types of perianal Paget's disease. One type has endodermal differentiation with gastrointestinal-type glands containing intraluminal dirty necrosis, numerous signet ring cells, CK20 positivity, and GCDFP15 negativity. Such cases are especially likely to be associated with synchronous or metachronous rectal adenocarcinoma. The other type is a primary cutaneous intraepithelial neoplasm in which the Paget's cells display sweat gland differentiation, including GCDFP15 positivity; it generally lacks gastrointestinal-type glands, intraluminal dirty necrosis, and CK20 positivity. The CK7 is a sensitive, albeit nonspecific, marker for Paget's cells.