Large cell neuroendocrine carcinoma of the distal common bile duct: A case report and literature review

Figure 1 Magnetic resonance image. A: Magnetic resonance cholangiopancreatography showed segmental interruption of the middle and distal common bile duct (arrow) with marked dilatation of the upstream intrahepatic and extrahepatic bile ducts; B: Contrast-enhanced magnetic resonance imaging in the arterial phase reveals a heterogeneous enhancing nodular mass measuring approximately 16 mm × 14 mm in the distal common bile duct (arrow); C: Portal venous/delayed phase demonstrates rapid washout of the mass.

Figure 2 Histopathological examination of the resected specimen. A: Gross appearance. The resected specimen revealed a nodular, protuberant mass in the distal common bile duct measuring 2 cm × 1.5 cm × 1 cm, located 0.6 cm from the cystic duct confluence and 5.5 cm from the duodenal papilla. The cut surface was grayish-white and firm in consistency; B: Microscopic findings (hematoxylin and eosin staining, × 200) – the tumor was composed of large cells arranged in nests and sheets. The tumor cells exhibited abundant cytoplasm, coarse chromatin, prominent nucleoli, and brisk mitotic activity (> 10/high-power field); C: Microscopic findings (hematoxylin and eosin staining, × 200) - a focal moderately differentiated adenocarcinoma component is identified, accounting for approximately 10% of the tumor volume; D: Immunohistochemistry (× 200) showing diffuse cytoplasmic positivity for synaptophysin; E: Immunohistochemistry (× 200) showing focal cytoplasmic positivity for chromogranin A (CgA); F: Ki-67 immunohistochemistry (× 200) showing a proliferation index of approximately 60%; G: Mismatch repair (MMR) protein immunohistochemistry (× 200) showing retained nuclear expression of MLH1, MSH2, MSH6, and PMS2, consistent with a proficient MMR phenotype.

Figure 3 Clinical timeline. March 2025 [admission, multidisciplinary team (MDT)] → April 2, 2025 (percutaneous transhepatic cholangial drainage) → April 14, 2025 (laparoscopic pancreaticoduodenectomy) → postoperative pathology (large cell neuroendocrine carcinoma, proficient mismatch repair, R1) → MDT discussion [exclusion of immunotherapy, selection of etoposide plus (EP) regimen] → May–August 2025 (EP × 6 cycles) → September 2025 (negative computed tomography) → April 2026 (last follow-up, disease-free survival). MDT: Multidisciplinary team; PTCD: Percutaneous transhepatic cholangial drainage; LPD: Laparoscopic pancreaticoduodenectomy; EP: Etoposide plus cisplatin; LCNEC: Large cell neuroendocrine carcinoma.