Poorly Differentiated Adenocarcinoma of Anal canal Presenting as a Vulval Lump

Abstract

Primary adenocarcinoma of the anal canal is a rare malignancy, accounting for fewer than 10% of anal cancers. It often presents with non-specific perianal symptoms and can be clinically mistaken for benign conditions such as a perianal abscess or Bartholin’s cyst, leading to diagnostic delay. A 69-year-old postmenopausal multipara woman presented with a three-month history of a painless, hard mass extending from the left labia majora to the left gluteal fold. She initially underwent incision and drainage for a presumed perianal abscess. Histopathological report of the excised tissue revealed poorly differentiated adenocarcinoma. Subsequent workup, including serum carcinoembryonic antigen (CEA) (2.02 ng/mL), chest x-ray, abdominal ultrasound, and CT-guided FNAC of a right lung mass, confirmed metastatic adenocarcinoma. Imaging revealed multiple pulmonary nodules in both lungs with right-sided pleural effusion, cholelithiasis, and mild endometrial collection. On immunohistochemistry (IHC), the perianal tissue sections demonstrated poorly differentiated adenocarcinoma. Our final diagnosis was carcinoma of the anal canal (Grade II, poorly differentiated adenocarcinoma) with pulmonary metastases. This case highlights that a hard, painless labio-gluteal lump in an older woman should raise suspicion for anal canal adenocarcinoma rather than benign inflammatory lesions. Early diagnosis and metastatic evaluation are essential to guide appropriate oncological management.  

CBMJ 2026 July: Vol. 15 No. 02 P:409-413