Rectal Phenotype of Perianal Paget Disease: Rare Concomitant Phenomena.

Abstract

Classically, 'Paget disease' refers to a distinct histological pattern in breast carcinoma. Here, we review the clinicopathological features of anorectal adenocarcinoma with 'pagetoid' spread. Histological and immunohistochemical records for 11 cases of anorectal adenocarcinoma with pagetoid spread among 958 Japanese patients with primary rectal/anal carcinoma were reviewed. Grossly, nine of 11 cases had areas of invasive carcinoma: Tubular adenocarcinoma in eight and neuroendocrine carcinoma in one. Pagetoid components were positive for cytokeratin 7 in eight cases, cytokeratin 20 and caudal type homeobox 2 in all 11 cases, and p63 in one case, but were negative for estrogen receptor, progesterone receptor, human epidermal growth factor receptor 2 (HER2), gross cystic disease fluid protein-15, and GATA binding protein 3. The prevalence of perianal Paget disease in this series was 1.1%, with two cases of genuine perianal Paget disease with a rectal phenotype without invasive carcinoma. The rectal phenotype of perianal Paget disease may not be associated with HER2 overexpression.