Coexistent poorly-differentiated neuroendocrine cell carcinoma and non-invasive well-differentiated adenocarcinoma in tubulovillous adenoma of the rectum: report of a case.

A 74-years old man was referred to our hospital for treatment of a rectal mass. Colonoscopy revealed villous tumor covering all the lower rectal lumen. Biopsy yielded a diagnosis of adenoma. CT examination showed tumor shadows of the rectum and the liver. Pelvic MRI examination showed a 10.5×8×7 cm tumor with high signal intensity on the T2 weighted images in the rectum. Rectosigmoidectomy with lymph node dissection was performed with the diagnosis of rectal cancer that metastasized to the liver. Histological and immuno- histochemical features showed coexistent poorly-differentiated small cell neuroendocrine cell (NEC) carcinoma and non-invasive well-differentiated adenocarcinoma in tubulovillous adenoma. However the chemotherapy with FOLFOX and Bevacizumab was performed postoperatively, the patient died in cancer 3 months after surgery. Rectal poorly-differentiated NEC carcinomas are thought to be a tumor with a high malignant potential. Recently, the UICC TNM classifications of malignant tumors, 7th edition and the Guidelines for colorectal NEC tumors of European Neuroendocrine Tumor Society have been published. They would be evaluated, and effective multimodal therapy for NEC carcinomas should be established.