Primary peri‐anal adenocarcinoma of intestinal type – a new proposed entity

Aims The currently recognised subtypes of anal canal/peri‐anal adenocarcinoma are those arising from low rectal mucosa or columnar cuff, fistula‐related tumours and anal gland carcinoma. This report presents two examples of a hitherto undescribed subtype of peri‐anal adenocarcinoma with an intestinal phenotype. Methods and results A 74‐year‐old man had a peri‐anal tumour locally excised, whereas a 73‐year‐old female underwent an abdominoperineal resection for peri‐anal Paget's disease with an underlying carcinoma. Neither patient had a history of perineal fistulae, Crohn's disease or previous gastrointestinal neoplasia, and neither showed clinical, radiological or endoscopic evidence of another abdominal or pelvic tumour. Both resection specimens contained adenocarcinoma, which were similar in demonstrating an intestinal morphology and CDX2 immunopositivity. The man has shown a disease‐free outcome thus far, but the woman has suffered with nodal and pelvic recurrence within a few months of surgery. Conclusions The name ‘primary peri‐anal adenocarcinoma of intestinal type’ is proposed for this previously unrecognised subtype of perineal neoplasia. Awareness of its distinct existence – by recognising its intestinal morphology and immunophenotype while excluding metastasis from the intestinal tract – should help to collate data to determine its specific prognosis and to formulate its best management.