A rare case of signet-ring cell carcinoma associated with poorly differentiated adenocarcinoma of the non-ampullary duodenum.

Primary duodenal cancer is a rare entity accounting for only 0.3% of all gastrointestinal cancers. Histopathologically, most duodenal cancers are mucin-producing adenocarcinomas, 34% being poorly differentiated. Signet-ring cell (SRC) carcinoma is extremely uncommon in the duodenum. Herein, we report a rare case of SRC carcinoma associated with poorly differentiated adenocarcinoma of the non-ampullary duodenum in a 74-year-old woman. The patient was admitted to the hospital for persistent epigastric pain, significant weight loss and hypochromic microcytic anemia. Esophago-gastro-duodenoscopy revealed a protruded lesion, with ulceration in the second portion of the duodenum, above the papilla. The patient was referred to surgery and pancreatico-duodenectomy with lymph node dissection was performed. The tumor consisted predominately of SRCs, Periodic Acid Schiff (PAS)-Alcian blue positive. The tumor cells were CDX2, cytokeratin (CK) 7 and CK 18/8 positive, which suggested a primary upper gastrointestinal tract site of origin. Immunostaining for mucin (MUC) 2 and MUC5AC was also positive demonstrating the duodenal goblet cells differentiation with a mixed gastric-foveolar and intestinal phenotype. Based on the morphological features and the immunohistochemical profile, a diagnosis of SRC carcinoma associated with poorly differentiated adenocarcinoma of the non-ampullary duodenum was set.