A Case of Mixed Neuroendocrine-non-neuroendocrine Neoplasm (MiNEN) of the Distal Bile Duct

Abstract

An 82-year-old man presented to our hospital with fever and impaired hepatic function. Imaging studies confirmed wall thickening and stenosis of the distal bile duct. A biopsy revealed adenocarcinoma. We diagnosed the case as distal bile duct cancer cT2cN0cStage IB and performed subtotal stomach-preserving pancreaticoduodenectomy with D2 lymph node dissection. Histopathology of the resected specimen showed the lesion to be composed of two kinds of tumors;namely, adenocarcinoma and NEC (chromogranin positive, synaptophysin positive, and Ki-67:73.8%). This case was of combined /biphasic type where adenocarcinoma and NEC owned respective area (adenocarcinoma versus NEC was 40% vs 60%). NEC invaded deeper than adenocarcinoma, reaching to the subserosal layer (pT2, ITT:5mm, SS). No vascular and neurotic infiltration and lymph node metastasis were seen in both adenocarcinoma and NEC (pLy0, pV0, pN0). A CT scan conducted 9 months after the operation revealed appearance of multiple hepatic metastases, for that the patient is now on chemotherapy. In this case adenocarcinoma mainly existed in the membranous surface so that we had difficulties in making diagnosis of MiNEN preoperatively. Furthermore, it is likely that NEC components had infiltrated into deeper layers that might cause the hepatic metastasis.