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World J Clin Cases. Aug 26, 2026; 14(24): 123303
Published online Aug 26, 2026. doi: 10.12998/wjcc.123303
Large cell neuroendocrine carcinoma of the distal common bile duct: A case report and literature review
Bo-Qian Zheng, Ze-Cun Zheng, Hao Wang, Graduate School, Hebei Medical University, Shijiazhuang 050051, Hebei Province, China
Ze-Pu Wang, Department of Hepatobiliary and Pancreatic Surgery II, Hebei General Hospital, Shijiazhuang 050051, Hebei Province, China
Rui-Zeng Feng, Hong-Jie Wang, Graduate School, Hebei North University, Zhangjiakou 075000, Hebei Province, China
Hong-Fang Tuo, Second Department of Hepatobiliary and Pancreatic Surgery, Hebei Provincial People’s Hospital, Shijiazhuang 050051, Hebei Province, China
ORCID number: Bo-Qian Zheng (0009-0001-2239-1634); Rui-Zeng Feng (0009-0001-3460-9661); Ze-Cun Zheng (0009-0008-4154-1301); Hong-Jie Wang (0009-0007-1069-6928); Hong-Fang Tuo (0009-0009-7448-7492).
Author contributions: Wang ZP was responsible for manuscript drafting, data collection, and literature review; Zheng BQ performed pathological analysis and interpretation and contributed to manuscript drafting; Tuo HF was responsible for study conception, supervision, and final approval; Wang H, Feng RZ, and Zheng ZC contributed to the supplementation of key references; Wang HJ prepared the figures; all authors have read and approved the final manuscript.
AI contribution statement: AI tools were not used for any part of the scientific content, analysis, or writing of this manuscript. The authors assume full responsibility for the integrity, accuracy, and originality of the work.
Informed consent statement: Written informed consent was obtained from the patient for the publication of this case report and the accompanying images.
Conflict-of-interest statement: All authors declare that they have no conflicts of interest to disclose.
CARE Checklist (2016) statement: The authors have read the CARE Checklist (2016), and the manuscript was prepared and revised in accordance with the CARE Checklist (2016).
Corresponding author: Hong-Fang Tuo, Associate Professor, Second Department of Hepatobiliary and Pancreatic Surgery, Hebei Provincial People’s Hospital, No. 348 Heping West Road, Xinhua District, Shijiazhuang 050051, Hebei Province, China. tuohongfang2023@163.com
Received: May 18, 2026
Revised: June 18, 2026
Accepted: August 5, 2026
Published online: August 26, 2026
Processing time: 96 Days and 20.6 Hours

Abstract
BACKGROUND

Large cell neuroendocrine carcinoma (LCNEC) of the extrahepatic bile duct is an exceedingly rare and highly aggressive malignancy, accounting for < 0.2% of all extrahepatic bile duct tumors. Preoperative diagnosis is challenging, and early recurrence is common even after R0 resection. No standard treatment regimen has been established to date. Mismatch repair (MMR) status has important implications for immunotherapy indications; however, it has rarely been reported in biliary LCNEC.

CASE SUMMARY

A 73-year-old man presented with obstructive jaundice. Imaging revealed a distal common bile duct mass. After percutaneous transhepatic cholangial drainage for biliary decompression, laparoscopic pancreaticoduodenectomy was performed. Pathological analysis confirmed LCNEC with a minor adenocarcinoma component, positive bile duct margin, and proficient MMR (pMMR)/microsatellite stable (MSS) phenotype. The patient received six cycles of adjuvant etoposide plus (EP) cisplatin and remained progression-free at 12-months follow-up (April 25, 2026), with no evidence of recurrence on imaging.

CONCLUSION

Biliary LCNEC is a rare and aggressive tumor. The pMMR/MSS phenotype provides a molecular rationale for excluding immunotherapy and directs treatment toward platinum-based chemotherapy. Even with a positive margin (R1), individualized adjuvant EP chemotherapy can achieve short-term disease-free survival. Multidisciplinary-guided, molecularly driven individualized therapy is central to the management of such rare malignancies.

Key Words: Neuroendocrine carcinoma; Common bile duct; Pancreaticoduodenectomy; Multidisciplinary team; Case report

Core Tip: This case report describes a distal common bile duct large cell neuroendocrine carcinoma (LCNEC) with a positive bile duct margin (R1 resection). Comprehensive immunohistochemistry revealed a proficient mismatch repair (MMR)/microsatellite stable phenotype, providing a molecular basis for excluding postoperative adjuvant immunotherapy. This is the first report of MMR testing directly guiding treatment decisions in biliary LCNEC, and clinicians are advised to incorporate MMR testing as a routine examination for biliary neuroendocrine carcinoma to inform immunotherapy decisions. With effective systemic therapy, positive margin (R1) resection does not preclude the possibility of favorable short-term outcomes. Multidisciplinary management that integrates molecular pathology is key to individualized treatment of rare tumors.



INTRODUCTION

Neuroendocrine neoplasms (NENs) are a heterogeneous group of tumors originating from peptidergic neurons and neuroendocrine cells, most commonly found in the gastrointestinal tract and pancreas[1,2]. Primary NENs of the biliary system are exceedingly rare, accounting for < 0.5% of all gastroenteropancreatic NENs. Among these, poorly differentiated neuroendocrine carcinoma (NEC) represents only 0.19% of extrahepatic bile duct malignancies[1].

According to the World Health Organization (WHO) 2019/2022 classification of digestive system tumors, NENs are categorized into well-differentiated neuroendocrine tumors (NETs), poorly differentiated NEC, and mixed neuroendocrine/non-NEN. Biliary NEC is further subdivided into small cell NEC and large cell NEC (LCNEC); both of which display highly aggressive behavior with early lymph node metastasis and distant spread[3].

Preoperative diagnosis of biliary NEC is difficult. The clinical presentation (obstructive jaundice and abdominal pain) overlaps with that of bile duct adenocarcinoma. Nechi et al[4] reported that most patients lack typical early clinical symptoms; upper abdominal discomfort, pain, and jaundice are the primary reasons for seeking medical attention, with obstructive jaundice as the initial symptom in 56% of patients. Conventional imaging lacks specificity, and endoscopic biopsy frequently yields false-negative results because the tumor is located in the submucosa, covered by normal epithelium, or contains an adenocarcinoma component[5]. According to Kamiya et al[6], only approximately 16% of patients receive a definitive preoperative diagnosis.

At the molecular level, NEC is characterized by frequent TP53 (about 85.8%) and RB1 (about 38.7%) mutations[7]. Mismatch repair (MMR) status is equally critical: As reported by Kasi et al[8] and Marabelle et al[9], most NECs exhibit a proficient MMR (pMMR)/microsatellite stable (MSS) phenotype; a “cold tumor” phenotype with intrinsic resistance to immune checkpoint inhibitors (ICIs). Therefore, MMR status testing is essential for treatment decision-making; pMMR tumors do not respond to ICIs.

Currently, there is no standard treatment regimen for biliary NEC. Surgical resection remains the first-line option. However, according to Kim et al[10], the recurrence rate exceeds 70% even after R0 resection, with a median overall survival of only 9-15 months. Sorbye et al[11] applied platinum-based chemotherapy [(etoposide plus (EP)] to patients with gastrointestinal NEC (WHO G3), drawing on experience from small cell lung cancer, but evidence for its use in biliary NEC remains limited.

CASE PRESENTATION
Chief complaints

A 73-year-old man was admitted to the outpatient clinic of the Department of Hepatobiliary and Pancreatic Surgery, Hebei General Hospital in March 2025, presenting with a 3-day history of intermittent right upper abdominal pain, accompanied by progressive jaundice of the skin and sclera, and low-grade fever (maximum 37.8 °C).

History of present illness

The above symptoms began 3 days prior to admission. The pain was described as an intermittent dull ache located in the right upper quadrant without radiation. The jaundice progressively worsened, accompanied by dark urine and pruritus. The patient denied nausea, vomiting, or weight loss.

History of past illness

The patient had no prior medical history of hepatitis, diabetes mellitus, hypertension, or surgery. He denied alcohol consumption and smoking.

Personal and family history

The patient denied any family history of malignancy or hereditary tumor syndromes.

Physical examination

Vital signs on admission: Body temperature 37.8 °C, blood pressure 135/82 mmHg, heart rate 88 beats/minute, and respiratory rate 18 breaths/minute. Physical examination revealed marked jaundice of the skin and sclera. The abdomen was flat and soft, with mild tenderness in the right upper quadrant but no guarding or rebound tenderness. Murphy’s sign was negative. No abdominal masses were palpable. Bowel sounds were normal.

Laboratory examinations

Admission laboratory investigations: Total bilirubin 224.2 μmol/L (normal range: 3.4-20.5 μmol/L), direct bilirubin 150.8 μmol/L (0-6.8 μmol/L), alanine aminotransferase 58.6 U/L (10-40 U/L), aspartate aminotransferase 52.3 U/L (10-40 U/L), alkaline phosphatase 212 U/L (40-130 U/L), and γ-glutamyl transferase 189 U/L (8-58 U/L). Tumor markers: Carcinoembryonic antigen 2.67 μg/L (0-5 μg/L), α-fetoprotein 3.62 μg/L (0-7 μg/L), and carbohydrate antigen (CA)19-9 > 1000 U/mL (0-37 U/mL). Complete blood count showed mild leukocytosis (white blood cell count 12.07 × 109/L, normal range: 3.5 × 109-9.5 × 109/L). Hepatitis B and C serology was negative.

Imaging examinations

Contrast-enhanced abdominal computed tomography (CT) revealed thickening of the distal common bile duct wall with luminal narrowing and marked dilatation of the upstream intrahepatic and extrahepatic bile ducts (maximum diameter 16 mm). Magnetic resonance cholangiopancreatography (MRCP) demonstrated segmental interruption of the middle and distal common bile duct, with a nodular, slightly hyperintense signal on T2-weighted imaging measuring 16 mm × 14 mm (Figure 1A). Abdominal contrast-enhanced magnetic resonance imaging (MRI) in the arterial phase (LAVA+C sequence) showed a markedly heterogeneous enhancing nodular mass of approximately 16 mm × 14 mm in the distal common bile duct (Figure 1B), with rapid washout in the portal venous/delayed phase (Figure 1C). This hypervascular enhancement pattern differed from the progressive delayed enhancement typical of cholangiocarcinoma, raising the possibility of a NET. Chest CT revealed no pulmonary or mediastinal abnormalities. No distant metastasis was detected.

Figure 1
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.
MULTIDISCIPLINARY EXPERT CONSULTATION

Following admission, a multidisciplinary team (MDT) comprising hepatobiliary and pancreatic surgery, medical oncology, gastroenterology, radiology, ultrasound, interventional radiology, and pathology, conducted a systematic case discussion. The consensus was as follows: (1) Based on imaging findings and the markedly elevated CA19-9, the most likely diagnosis was distal bile duct carcinoma. Clinical staging [American Joint Cancer Committee (AJCC), 8th edition] was cT2N0M0, stage IIA. However, contrast-enhanced MRI features raised the suspicion of a NET; (2) In view of the severe obstructive jaundice and Child–Pugh class B (score 8), percutaneous transhepatic cholangial drainage (PTCD) was recommended to relieve jaundice and improve liver function before radical surgery; (3) Once liver function improved, laparoscopic pancreaticoduodenectomy (LPD) was planned as the curative procedure, with systematic lymphadenectomy of stations 8, 12, 13, and 16; and (4) The resected specimen should undergo comprehensive immunohistochemical analysis, including synaptophysin (Syn), chromogranin A (CgA), CD56, Ki-67, and MMR proteins (MLH1, MSH2, MSH6, and PMS2), to guide postoperative systemic therapy (Figure 2).

Figure 2
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.

Following the availability of postoperative pathological findings, the MDT reconvened to formulate an adjuvant treatment strategy. The tumor was a high-grade NEC (Ki-67: 60%) with a pMMR/MSS phenotype, thereby excluding the indication for ICIs. The EP regimen was selected as first-line chemotherapy[11] for a planned six cycles. The team considered that, for a systemic disease such as NEC, effective systemic therapy takes priority over local considerations of margin status. The patient agreed to this treatment plan.

FINAL DIAGNOSIS

LCNEC of the distal common bile duct, with a minor adenocarcinoma component (< 10%, consistent with LCNEC). Pathological stage: PT2N0M0, stage IIA (AJCC 8th edition, distal bile duct staging system).

TREATMENT

The patient had an uneventful postoperative recovery and was discharged on postoperative day 12. Adjuvant EP chemotherapy was initiated on May 13, 2025. The regimen for each cycle was as follows: Etoposide 0.1 g intravenously on days 1-3 and cisplatin 20 mg intravenously on days 1-5; the drugs were administered on days 1, 2, and 3 of each cycle, followed by a rest and recovery period, with cycles repeated every 3 weeks. The patient completed a total of six cycles (May 13 to August 31, 2025). Chemotherapy was well tolerated, with only grade 1 nausea and mild fatigue, requiring neither dose reduction nor treatment delay.

OUTCOME AND FOLLOW-UP

Follow-up contrast-enhanced abdominal CT performed after completion of chemotherapy (September 15, 2025) showed postoperative changes consistent with LPD. No local recurrence, hepatic metastasis, or lymphadenopathy was observed. The tumor marker CA19-9 decreased to 26.5 U/mL (within normal range). The patient was followed up regularly. At the most recent follow-up (April 25, 2026, 12 months postoperatively), the patient is alive and asymptomatic. Follow-up will continue every 3 months. The clinical timeline is illustrated in Figure 3.

Figure 3
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.
DISCUSSION

The diagnostic process of this case exemplifies an evidence-based clinical approach grounded in comprehensive clinical information. The patient presented with obstructive jaundice, right upper quadrant abdominal pain, and low-grade fever; a symptom complex highly suggestive of malignant biliary obstruction. Non-contrast CT showed thickening of the distal common bile duct wall with upstream biliary dilatation, and both MRCP and contrast-enhanced MRI clearly demonstrated the occupying lesion. Contrast-enhanced MRI revealed marked heterogeneous hyperenhancement in the arterial phase and rapid washout in the portal venous/delayed phase. This “fast-in, fast-out” enhancement pattern differs distinctly from the progressive delayed enhancement typical of bile duct adenocarcinoma. In recent years, the role of contrast-enhanced ultrasound in differentiating hepatobiliary tumors has been increasingly recognized[12-20]. In the study by Dong et al[21], NET lesions typically exhibited a fast-in, fast-out hemodynamic pattern, which is commonly observed in hypervascular tumors such as hepatocellular carcinoma. Their smooth contour may help distinguish them from the infiltrative and irregular margins characteristic of typical cholangiocarcinoma. Such imaging clues can provide a valuable reference for suspecting a non-adenocarcinoma origin during multidisciplinary preoperative discussions. In retrospect, several imaging features in this case could have raised preoperative suspicion of a NEN. Contrast-enhanced MRI demonstrated arterial hyperenhancement with rapid washout in the portal venous/delayed phase, a “fast-in, fast-out” pattern atypical for the progressively delayed enhancement of conventional cholangiocarcinoma. On MRCP, the lesion appeared as a relatively well-circumscribed, polypoid intraluminal filling defect without infiltrative margins and periductal desmoplastic reaction commonly associated with biliary adenocarcinoma. Prior studies have suggested that such features may favor a hypervascular tumor such as a NEN over conventional cholangiocarcinoma[21]. However, endoscopic ultrasonography with fine-needle aspiration (EUS-FNA) was not performed in this case, as the immediate priority was biliary decompression via PTCD. The absence of a preoperative cytological diagnosis represents a limitation, and EUS-FNA should be considered in future cases with atypical imaging findings to establish a preoperative diagnosis.

In establishing the diagnosis of primary biliary LCNEC, several entities must be excluded: (1) Poorly differentiated adenocarcinoma: The dominant histological pattern in this case was LCNEC (> 90%), confirmed by diffuse positivity for Syn and CgA, and a Ki-67 index of 60%. Poorly differentiated adenocarcinomas typically express CK7, CK20, and CDX2 without diffuse neuroendocrine marker expression; (2) Metastatic NEC from the lung or other sites: Preoperative chest CT showed no pulmonary mass, and the presence of an overlying high-grade intraepithelial neoplasia supported a primary biliary origin; and (3) Lymphoepithelioma-like carcinoma: This entity is characterized by nests of undifferentiated cells with dense lymphoplasmacytic infiltrate and Epstein-Barr virus association, neither of which was observed. Other rare biliary malignancies, such as clear cell carcinoma or sarcomatoid carcinoma, were excluded based on the absence of their respective morphological and immunohistochemical features.

The role of MMR status represents one of the key contributions in this case. The tumor expressed all four MMR proteins, indicating a pMMR/MSS phenotype. Tumors with pMMR display a low tumor mutational burden and a limited neoantigen load, thereby forming a noninflamed (cold) tumor microenvironment, and their objective response rate to ICIs is typically < 5%[9,12,20]. Conversely, deficient MMR/high microsatellite instability tumors, due to their high mutational burden, are highly sensitive to ICIs, with objective response rates reaching 30%-50%[22]. The definitive finding of pMMR in this patient enabled the team to exclude immunotherapy and concentrate on cytotoxic chemotherapy, thus avoiding ineffective treatment, immune-related adverse events, and additional economic burden.

NEC is characterized by high-frequency mutations in TP53 and RB1. In pulmonary LCNEC, RB1 mutation or loss of expression predicts greater sensitivity to SCLC-like regimens (EP platinum)[23]. International guidelines (National Comprehensive Cancer Network and European Society for Medical Oncology) recommend platinum-based combination chemotherapy for high-grade NEC. The NORDIC NEC study demonstrated that the EP regimen (EP cisplatin) achieves a superior objective response rate in gastroenteropancreatic NEC with Ki-67 > 55%[11], and RB1-mutant pulmonary LCNEC is similarly sensitive to such SCLC-like regimens[23]. The choice of EP in this case is based on the following factors: (1) The Ki-67 index of approximately 60%, matching the EP-favored population; (2) Cisplatin is the standard agent in pivotal studies like NORDIC, with stronger evidence in NEC than carboplatin or gemcitabine plus cisplatin; and (3) With an ECOG performance status of 0 and normal renal function, the MDT established a specific dosing schedule (etoposide 0.1 g on days 1-3, cisplatin 20 mg on days 1-5, every 3 weeks) to balance efficacy and safety. Prospective data for biliary tract NEC remain limited, and the optimal platinum-based regimen awaits further investigation.

Traditional biliary oncology emphasizes the prognostic value of R0 resection. This case challenges that tenet: In the context of NEC, the patient achieved 12-month disease-free survival despite a positive hepatic duct margin. The likely explanation lies in the systemic nature of NEC; even patients with apparently localized disease on imaging may harbor radiographically occult micrometastases. The literature indicates that recurrence predominantly manifests as distant metastasis (liver, lung, and peritoneum) and occurs within 3-6 months postoperatively[3,10,14,15]. Therefore, for biliary NEC, effective systemic therapy may outweigh margin status in prognostic importance. Surgery should aim to relieve biliary obstruction, obtain tissue for pathological and molecular classification, and achieve macroscopic tumor clearance when feasible. Adjuvant chemotherapy such as EP should be initiated as early as possible postoperatively, regardless of margin status, provided the patient’s general condition permits.

This case fully exemplifies the central role of the MDT in managing rare malignancies (Table 1). From preoperative staging decisions and surgical planning to the postoperative formulation of chemotherapy based on MMR status, the MDT made decisive contributions at multiple critical junctures. Without MDT involvement, the molecular information regarding pMMR might have been overlooked, and the patient may have received ineffective immunotherapy or no systemic treatment at all. The MDT workflow integrating molecular pathology demonstrated in this case is generalizable to the management of other rare tumors.

Table 1 Key contributions of the multidisciplinary team at major decision nodes.
Treatment stage
Core contributions of MDT
DiagnosisDepartment of Radiology and Ultrasound interpreted the “fast-in, fast-out” imaging features of the lesion, suggesting the possibility of a neuroendocrine tumor
PreoperativeDepartment of Interventional Radiology performed percutaneous transhepatic cholangiography and drainage to ensure surgical safety; the Department of Surgery formulated the surgical plan for laparoscopic pancreaticoduodenectomy
PathologyComprehensive immunohistochemical tests (including MMR protein testing) were performed, confirming proficient MMR and excluding indications for immunotherapy
Adjuvant therapyDepartment of Medical Oncology formulated the EP regimen; the Department of Pathology reconfirmed no indications for immune checkpoint inhibitor therapy
Follow-upMultidisciplinary coordination completed imaging reexamination and clinical efficacy evaluation

To our knowledge, this is the first biliary LCNEC case in which MMR status directly informed the exclusion of immunotherapy. The pMMR/MSS phenotype predicts poor ICI response, with a response rate consistently below 5% in colorectal and gastroesophageal adenocarcinomas[9,12], although dedicated data for biliary NEC are lacking. Our decision rested on three considerations. First, intact MMR protein expression indicated a low tumor mutational burden and a non-inflamed (“cold”) tumor microenvironment. Second, high-grade NECs share conserved molecular features across anatomic sites, including frequent TP53/RB1 mutations and a typically “cold” immune landscape[7], allowing reasonable extrapolation from other gastrointestinal NECs. Third, no MSI-H/dMMR case has been reported among all biliary NECs tested to date[19], further arguing against ICI benefit. However, the current evidence remains indirect, and prospective studies are required to validate pMMR/MSS as a predictive biomarker specifically in biliary NEC (Table 2).

Table 2 Summary of individual patient data from the literature review (24 representative cases out of 49 total patients included in the analysis).
Ref.
Age (year)
Sex
Histology
Surgical procedure
Resection margin
Adjuvant chemotherapy
Overall survival (months)
Outcome
Sasatomi et al[3], 201376MLCNEC (pure)Right hepatectomy + bile duct resectionR0None< 1 (21 days)DOD
Kamiya et al[6], 202084MNEC with adenosquamous ca. (MiNEN)PancreaticoduodenectomyNRNo (rapid progression)3DOD
Kim et al[10], 201166FNEC (gallbladder)Extended cholecystectomyR0None13.7DOD
Kim et al[10], 201169MNEC (bile duct)PancreaticoduodenectomyR0NR11.6DOD
Kim et al[10], 201156MNEC (ampulla)PancreaticoduodenectomyR0None> 102.1NED
Kim et al[10], 201160FMANEC (gallbladder)Extended cholecystectomyR0NR33.9DOD
Kim et al[10], 201154MMANEC (bile duct)PancreaticoduodenectomyR0NR5.2DOD
Murakami et al[14], 201680MLCNEC + Adenoca. (MiNEN)Extrahepatic bile duct resectionR0No (poor condition)3DOD
Park et al[15], 201475FLCNEC (pure)CBD excision + HJR05-FU + epirubicin + cisplatin12DOD
Park et al[17], 202260FLCNEC + Adenoca. (MiNEN)Left hepatectomy + caudatectomyNREP × 6 cycles7+NED
Park et al[17], 202267MLCNEC + Adenoca. (MiNEN)PPPDNREP × 6 cycles7+NED
Sato et al[18], 200668MLCNEC + Adenoca. (MiNEN)PancreaticoduodenectomyNRNR3DOD
Liu et al[19], 202663MSCNEC (distal bile duct)PancreaticoduodenectomyR0EP (after recurrence)25.3 (759 days)DOD
Liu et al[19], 202677MSCNEC (distal bile duct)PancreaticoduodenectomyR0None22.5 (674 days)DOD
Liu et al[19], 202661MLCNEC (gallbladder)Cholecystectomy + IVb/V resectionR0EP (after recurrence)10.1 (302 days)DOD
Liu et al[19], 202657FSCNEC (gallbladder)Cholecystectomy + IVb/V resectionR1None7.7 (230 days)DOD
Liu et al[19], 202672FSCNEC (gallbladder)Cholecystectomy + IVb/V resectionR0None26.0 (781 days)DOD
Liu et al[19], 202667FSCNEC (gallbladder)Cholecystectomy + IVb/V resectionR0None15.5 (465 days)DOD
Liu et al[19], 202665FLCNEC (hilar)CBD resection + HJR0None20.8 (624 d)DOD
Liu et al[19], 202667FSCNEC (hilar)CBD resection + HJR0None31.8 (953 days)DOD
Liu et al[19], 202657FNR (hilar)CBD resection + HJR0None2.2 (67 days)Alive
Zhang et al[16], 202575MLCNEC + Adenoca. (MiNEN)Laparoscopic radical resectionR0Declined6 (then recurrence)AWD
Park et al[20], 201859MLCNEC (pure)Radical CBD excision + HJR1EP + radiotherapy10+NED
Present case (2026)73MLCNEC + Adenoca. (MiNEN)Laparoscopic PDR1 (bile duct)EP × 6 cycles12+NED

The strengths of the study were as follows: (1) This is the first explicitly documented case in biliary LCNEC of MMR testing directly influencing treatment decisions; (2) It demonstrates that with effective systemic therapy, short-term progression-free survival can still be achieved despite R1 resection; and (3) It presents in detail an MDT workflow that is generalizable to other rare tumors.

This study had some limitations: (1) The follow-up duration was short (12 months); (2) Long-term survival and recurrence risk remain undefined; (3) Conclusions regarding causality cannot be drawn from a single case; (4) RB1 mutation testing was not performed; and (5) 68Ga-DOTATATE PET/CT was not performed, and therefore somatostatin receptor expression and the possibility of peptide receptor radionuclide therapy were not evaluated.

CONCLUSION

This case highlights the pivotal role of molecular pathology in guiding individualized treatment for rare biliary NENs. The identification of a pMMR/MSS phenotype provided a molecular rationale for excluding ICI and directing therapy toward platinum-based chemotherapy, which resulted in sustained 12-month disease-free survival. The key clinical implications are as follows: (1) MMR status should be routinely assessed in all biliary NECs, as patients with pMMR/MSS tumors are unlikely to benefit from ICIs; (2) Effective systemic therapy is critical for improving outcomes and should not be deferred due to margin status; and (3) MDT integration of molecular pathology represents the core model for managing rare tumors and is generalizable to other rare malignancies. Prospective studies are warranted to further validate these molecularly driven strategies in biliary NEC.

ACKNOWLEDGEMENTS

The authors thank all members of the hepatobiliary tumor multidisciplinary team at Hebei General Hospital for their dedicated collaboration, and the patient for his trust and cooperation.

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Footnotes

Peer review: Externally peer reviewed.

Peer-review model: Single blind

Corresponding Author's Membership in Professional Societies: Surgical Rapid Rehabilitation Committee; Biliary Tract Tumor Committee, Hebei Anti-Cancer Association; Hebei Medical Association; Deputy Head, Laparoscopic and Endoscopic Surgery Group.

Specialty type: Medicine, research and experimental

Country of origin: China

Peer-review report’s classification

Scientific quality: Grade B, Grade D

Novelty: Grade C, Grade D

Creativity or innovation: Grade C, Grade C

Scientific significance: Grade B, Grade C

P-Reviewer: Guo C, Academic Fellow, China; Takahashi K, MD, Japan S-Editor: Liu H L-Editor: Webster J P-Editor: Wang WB

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