2026 Volume 68 Issue 4 Pages 315-320
Anal canal carcinomas are rare and frequently diagnosed at an advanced stage. Here, we present the case of a 59-year-old man with early-stage anal canal adenocarcinoma surrounded by squamous epithelium. Lower gastrointestinal endoscopy revealed a 20-mm erythematous lesion (type 0-Ⅱa+Ⅰs) contiguous with the anal canal and entirely surrounded by squamous epithelium. Biopsy confirmed anal canal adenocarcinoma based on irregular glandular duct structures and atypical blood vessels of unequal caliber in an erythematous, elevated area surrounded by squamous epithelium. Endoscopic submucosal dissection was performed because there was no definitive evidence of deep submucosal invasion. Immunohistochemistry demonstrated that the specimens were CK7(+), CK20(+), and CDX2(+), consistent with rectal-type anal canal adenocarcinoma. Despite the diagnostic challenge posed by the surrounding squamous epithelium, histological and immunohistochemical analysis facilitated appropriate therapeutic management.
