Four cases of early stage poorly differentiated non-ampullary duodenal adenocarcinoma: a case report.

Early-stage, poorly differentiated, non-ampullary duodenal adenocarcinomas are rare, and their clinicopathological features remain unelucidated. Between September 2006 and April 2022, 205 consecutive patients underwent endoscopic or surgical resection for early-stage non-ampullary duodenal adenocarcinomas at our hospital. There were no cases of poorly differentiated adenocarcinoma among the 188 cases of mucosal carcinoma. Meanwhile, among the 17 cases of submucosal invasive carcinoma, four cases were poorly differentiated adenocarcinomas. Herein, we report four cases of these carcinomas. All four lesions were reddish in color and were located on the oral side of the papilla. The gross types were either protruded (0-I) or mixed, elevated, and depressed (0-IIa + IIc). During preoperative diagnosis, submucosal invasion was suspected in all lesions, and biopsies were performed. Based on histological analyses of biopsy specimens, a diagnosis of poorly differentiated or signet-ring cell components was made in all cases, and a pancreaticoduodenectomy was performed. The median tumor size was 6.5 (range, 5-12) mm, and all lesions were poorly differentiated adenocarcinomas with submucosal invasion and lymph node metastasis. Regarding the tumor immunophenotype, one and three cases exhibited gastric and mixed gastrointestinal phenotypes, respectively. Two patients experienced metastatic recurrence; one of them died from the primary disease.