Papillary immature squamous metaplasia of the anal canal: a rare but probably underdiagnosed entity

A 63-years-old man presented with a condylomatous hemicirconferential exophytic lesion of the anal canal. He had a history of anal squamous cell carcinoma, cT2N0M0, treated by radiochemotherapy and some recurrent condylomata treated by electrocoagulation. Given this background as well as the morbidity of an abdominoperineal amputation, a mucosectomy was performed. Histopathological examination demonstrated a squamous mucosa with papillary architecture, lined by a population of immature cells (Fig. 1). There was only little maturation. P16 immunohistochemistry remained negative. Ki-67 immunohistochemistry was positive essentially in the lower half of the epithelium, with some rare positive cells in the upper layers (Fig. 2). A diagnosis of papillary immature metaplasia of the anal canal was made.