Basosquamous carcinoma of the perianal skin accompanied by in－transit metastasis

Abstract

A man in his 50s presented with an approximately 35－year history of a nodule on the perianal skin. The patient recently observed purulent discharge from the lesion. Clinical examination showed a black, flat, elevated ulcerated nodule (2.5×1.4 cm) in addition to a perineal subcutaneous nodule (7 mm). Skin biopsy showed cord－like proliferation of atypical basaloid cells with some cornification, which suggested basosquamous carcinoma. We performed excisional biopsy of the perineal subcutaneous lesion and inguinal sentinel lymph node. Histopathological examination of the perineal subcutaneous nodule showed in－transit metastasis of the perianal tumor, and the sentinel node biopsy showed negative results. Diagnosis of basosquamous carcinoma was confirmed following primary tumor removal. Owing to the high malignant potential of basosquamous carcinoma, careful physical examination and diagnostic imaging are warranted, and sentinel node biopsy, similar to that performed in cases of squamous cell carcinoma, is recommended.[Skin Cancer (Japan) 2024 ; 39 : 14－19]