A Case of Poorly Differentiated Early Rectal Adenocarcinoma with Tubulo-Villous Adenoma

Abstract

A 42-year-old man with bloody stool was found in barium enema and colonoscopy to have a polypoid lesion 20 mm with an irregular surface and fold convergence in the rectum. Biopsies were consistent with poorly differ-entiated adenocarcinoma. Given the patient's disability, we conducted Hartmann's operation. Histological ex-amination showed poorly differentiated adenocarcinoma invading the submucosal layer with lymphnode meta-stasis. The poorly differentiated adenocarcinoma was encircled by tubulovillous adenoma. No point mutation of the K-ras gene was observed in the poorly differentiated adenocarcinoma or tubulovillous adenoma. Immunohistochemically, only the poorly differentiated adenocarcinoma showed diffuse positive staining for p53 protein. Based on the pathological figure and molecular biological analysis, this case was definitively diag-nosed as poorly differentiated adenocarcinoma following a pathway included in the adenoma-carcinoma se-quence.