Duodenal Adenocarcinoma Recurrence Limited to the Choledochojejunostomy After Pancreaticoduodenectomy: A Case Suggesting Intraluminal Implantation With a Distinct Mucin Phenotypic Shift

Objective: Unusual clinical course Background:Intraluminal implantation of adenocarcinoma is well recognized, traditionally explained by the presence of exfoliated carcinoma cells (ECCs) and surgically created raw mucosal surfaces.However, whether phenotypic alterations of ECCs contribute to intraluminal implantation has not been systematically investigated. Case Report:A 59-year-old man with duodenal adenocarcinoma developed recurrence at the choledochojejunostomy site 27 months after pancreaticoduodenectomy, despite the presence of 5 surgically created raw surfaces.Tumor cells in the recurrent lesion showed an intestinal immunophenotype (CK7-/CK20+) identical to that of the primary tumor, but a distinct phenotypic shift was observed.The recurrent tumor showed MUC5AC and MUC2, which were absent in the primary tumor.In contrast, MUC6 and CA19-9, both present in the primary lesion, were not detected in the recurrent lesion.Experimental studies in several epithelial malignancies suggest bile acids may modulate mucin expression, including MUC5AC, and activate tumor-associated signaling pathways.The findings in this case are compatible with intraluminal implantation and raise the possibility that bile acid-associated phenotypic modulation of ECCs, most notably reflected by the difference in MUC5AC expression between the primary and recurrent lesions, may have contributed to this unusual recurrence pattern.Radiotherapy resulted in temporary local control; however, the patient subsequently developed peritoneal carcinomatosis and died 54 months after pancreaticoduodenectomy. Conclusions:Intraluminal implantation may proceed through sequential steps including attachment, engraftment, niche formation, and outgrowth.Although the extent of raw surfaces and the burden of ECCs are central to the attachment phase, we propose a novel hypothesis that phenotypic modulation of ECCs may also be an important determinant of engraftment and the later stages of intraluminal implantation.