Multimodal Treatment Approach for Mixed Neuroendocrine-Non-Neuroendocrine Neoplasms of the Gallbladder: A Patient with a Favorable Survival Outcome

Abstract

Mixed neuroendocrine-non-neuroendocrine neoplasm of the gallbladder (GB-MiNEN) is an exceptionally rare and aggressive tumor with no established treatment guidelines. We herein present the case of a 53-year-old woman with GB-MiNEN who was treated with irinotecan and cisplatin therapy, which led to a significant tumor reduction and subsequent conversion surgery. Despite a later recurrence, multimodal therapy extended survival for over two and a half years. This case underscores the potential benefit of conversion surgery combined with systemic chemotherapy, thus suggesting that multimodal treatment may improve the outcomes of GB-MiNEN. Our findings highlight the need for further studies to optimize the treatment strategies for this rare malignancy.

Introduction

Neuroendocrine neoplasms (NENs) arise from neuroendocrine cells and occur in every organ (1). Although NENs commonly occur in the lungs, pancreas and gastrointestinal tract, NEN of the gallbladder (GB-NEN) is extremely rare. Mixed neuroendocrine-non-neuroendocrine neoplasm (MiNEN) with a mixture of neuroendocrine carcinoma (NEC) and adenocarcinoma components is rare. NEC, a component of MiNEN, is a poorly differentiated neuroendocrine carcinoma with a worse prognosis than other neuroendocrine tumors (NETs) (2). Surgical therapy is regarded as the most effective treatment for achieving a long-term survival in patients with MiNENs. However, there are many uncertainties regarding the appropriate treatment options for GB-MiNEN.

We herein report a case in which GB-MiNEN responded markedly to irinotecan and cisplatin (IP) therapy, allowing us to thereafter perform conversion surgery. However, ureteral metastasis was later observed, and chemotherapy was continued. We performed multimodal treatment for more than two and a half years after the initial diagnosis. GB-MiNEN is generally associated with a poor prognosis; however, we describe a case of GB-MiNEN that achieved a relatively favorable treatment outcome.

Case report

The patient was a 53-year-old woman with no relevant medical history. She had no family history of multiple endocrine neoplasias or any other hereditary diseases. She visited a local doctor due to high levels of tumor markers [(carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9)] at a physical checkup in February 2022. An abdominal ultrasound examination revealed mass lesions at the bottom of the GB and the GB bed of the liver; therefore, she was referred to our hospital. No abnormal findings were found on physical examination, and no hormone-related symptoms were observed. Except for tumor markers, the laboratory findings were within the normal range (Table). The tumor markers were as follows: CEA was 8.8 ng/mL (normal range; ＜3.5 ng/mL); and CA19-9 was 38.2 U/mL (normal range; ＜37.0 U/mL); neuron-specific enolase (NSE) was 70.4 ng/mL (normal range; ＜16.3 ng/mL). Contrast-enhanced computed tomography (CT) showed a mass with contrast enhancement in the fundus of the GB and two metastatic tumors in the liver (S5). Additionally, the lymph nodes in the hepatoduodenal ligament and posterior pancreatic head were enlarged (Fig. 1a-d). Positron emission tomography (PET)-CT also showed an abnormal accumulation in these areas (Fig. 1e, f). Endoscopic ultrasound (EUS) identified tumors in both the GB fundus and enlarged lymph nodes, and fine-needle aspiration (FNA) was performed on the enlarged lymph nodes (data not shown). Hematoxylin and Eosin (H&E) staining of FNA specimens showed tumor cells with moderate-sized round to spindle-shaped nuclei and scant cytoplasm. They proliferated in sheets and in a honeycomb pattern, accompanied by hemorrhaging and necrosis (Fig. 2a). Immunohistochemical staining was positive for synaptophysin, CD56, and chromogranin. Ki-67 staining was positive in approximately 80% of cells (Fig. 2b-e). No adenocarcinoma components were identified in the pathological evaluation of the FNA specimens. Therefore, the patient was diagnosed to have small cell neuroendocrine carcinoma. There were no indications for surgery, and IP therapy was started in April 2022. After four courses of IP therapy, CT showed that the GB tumor had shrunk markedly and the swollen lymph nodes had disappeared. The liver metastases also disappeared (Fig. 3a-c). The abnormal uptake on PET-CT also disappeared (Fig. 3d). All tumor markers were within the normal ranges. Although a partial response was obtained with chemotherapy, it was considered difficult to obtain a complete response by continuing chemotherapy in the future. Since the tumor was significantly reduced and the liver metastasis had disappeared, conversion surgery was judged to be possible, and in September 2022, after 7 courses of chemotherapy, surgical treatment (extended cholecystectomy, extrahepatic bile duct resection, hepaticojejunostomy, regional lymph node dissection) was performed. Regarding the postoperative pathology, only one metastasis was observed in lymph node #12, and R0 resection was performed. H&E staining showed proliferation of atypical small oval cells with hyperchromatic nuclei and scant cytoplasm arranged in nests or cords, often displaying a rosette formation with brisk mitotic activity invading the serosa, together with proliferation of atypical columnar or cuboidal epithelial cells with hyperchromatic nuclei and eosinophilic cytoplasm replacing the mucosal epithelium and invading as far as the subserosa of the GB wall (Fig. 4a). Immunohistochemically, atypical small cells were positive for synaptophysin, insulinoma-associated protein 1 (INSM1), and chromogranin A. Ki-67 was positive in approximately 90% of the cells. Additionally, somatostatin receptor 2 (SSTR2) expression was strongly positive (Fig. 4d-h). Atypical columnar to cuboidal cells were negative for synaptophysin, chromogranin A, INSM1, and SSTR2 (data not shown). The pathological diagnosis was MiNEN, with a mixture of NEC and adenocarcinoma components. The postoperative course was uneventful, and the patient was discharged 11 days postoperatively. Since preoperative IP therapy was remarkably effective, we decided to continue IP therapy after surgery and performed 5 postoperative courses, for a total of 13 courses. However, the patient experienced severe fatigue due to cisplatin, and at the patient's request, treatment was switched to oral tegafur gimeracil-oteracil-potassium (S-1). Metastasis and recurrence to the right ureter were detected in July 2023, and etoposide and cisplatin (EP) therapy was initiated (Fig. 5a). After three courses of EP therapy, tumor progression was observed (Fig. 5b). As GB-MiNEN is also a type of GB-cancer, treatment with an immune checkpoint inhibitor (ICI) was expected to be effective, and durvalumab plus gemcitabine and cisplatin (GCD) therapy was initiated in November 2023. However, after six courses, further tumor enlargement was observed, along with the appearance of liver metastasis (Fig. 5c). GCD therapy was considered for the progressive disease (PD), and gemcitabine and carboplatin (GC) therapy was initiated in June 2024. Despite receiving GC therapy, the patient's performance status declined, thus making it difficult to continue treatment. The treatment plan was shifted to the best supportive care, and the patient passed away in September 2024, two years and six months after the initial diagnosis.

Table.

Laboratory Data at the First Visit to Our Hospital.

Hematology			Blood chemistry			Tumor marker
WBC	4,700	/μL	TP	6.7	g/dL	CEA	8.8	ng/mL
RBC	450×104	/μL	Alb	4.5	g/dL	CA19-9	38.2	U/mL
Hb	13.4	g/dL	T-Bil	0.9	mg/dL	NSE	70.4	ng/mL
MCV	91.7	μm3	AST	18	U/L
PLT	26.0×104	/μL	ALT	13	U/L	Viral marker
			ALP	68	U/L	HBs Ag	(-)
Serology			γ-GTP	18	U/L	HBc Ab	(-)
CRP	0.02	mg/dL	LDH	205	U/L	HCV Ab	(-)
			CK	76	U/L
Coagulation			BUN	7	mg/dL
PT-%	100	%	Cr	0.55	mg/dL
APTT	26.9	s	Na	143	mmol/L
			K	4.4	mmol/L
			Cl	105	mmol/L

Figure 1.

Contrast-enhanced computed tomography (CT) images in the arterial phase (a, b) and equilibrium phase (c, d) reveal a contrast-enhancing mass in the fundus of the gallbladder (yellow arrowhead) and two metastatic tumors in segment 5 of the liver (red arrowheads). Additionally, enlarged lymph nodes were noted in the hepatoduodenal ligament (yellow circle) and the posterior pancreatic head (red circle). (e, f) Positron emission tomography-CT showing an abnormal accumulation in these areas.

Figure 2.

Histological examinations of the fine-needle aspiration specimens. (a) Hematoxylin and Eosin staining (100×, scale bar=100 μm) showed tumor cells with moderate-sized round to spindle-shaped nuclei and scant cytoplasm, proliferating in sheets and a honeycomb pattern, accompanied by hemorrhaging and necrosis. (b-e) Immunohistochemical staining was positive for synaptophysin and CD56, with chromogranin A-positive cells also observed. Ki-67 staining indicated a proliferation index of approximately 80%.

Figure 3.

(a, b, c) Contrast-enhanced computed tomography (CT) images showed that the tumor of the gallbladder had shrunk markedly (yellow arrowhead) and the swollen lymph nodes had disappeared (yellow and red circle). (d) Liver metastases also disappeared (red arrowhead in a). (e) The abnormal uptake on positron emission tomography -CT also disappeared.

Figure 4.

Pathological examination of the surgical specimen. (a: 40×, scale bar=100 μm) Hematoxylin and Eosin staining shows distinct components of mixed neuroendocrine non-neuroendocrine neoplasm, highlighted by yellow and red circles. (b: 100×, scale bar=100 μm) The yellow-circled area represents the neuroendocrine carcinoma (NEC) component, displaying atypical small oval neuroendocrine cells with hyperchromatic nuclei and scant cytoplasm, arranged in nests or cords with rosette formation and brisk mitotic activity, invading down to the serosa. (c: 100×, scale bar=100 μm) The red-circled area highlights the adenocarcinoma component, consisting of atypical columnar or cuboidal epithelial cells with hyperchromatic nuclei and eosinophilic cytoplasm, replacing the mucosal epithelium and invading down to the subserosa of the gallbladder wall. (d-h: 100×, scale bar=100 μm) immunohistochemistry staining of the NEC cells. The atypical small cells are positive for synaptophysin, insulinoma-associated protein 1, and chromogranin A, with a high Ki-67 index of approximately 90%. Additionally, the somatostatin receptor 2 expression was strongly positive.

Figure 5.

(a) After irinotecan and cisplatin and tegafur gimeracil-oteracil-potassium therapy. Computed tomography showed metastasis and recurrence to the right ureter. (b) After three courses of EP therapy. (c) After six courses of durvalumab plus gemcitabine and cisplatin therapy, further tumor enlargement was observed.

Discussion

NENs can occur in various organs of the body. However, the GB is devoid of neuroendocrine cells; thus, when NEN arises in the GB, metaplastic changes are hypothesized to occur in the GB mucosa (3). In the present case, we encountered a rare form of GB-MiNEN. MiNEN is defined as a tumor comprising at least 30% of NEC and adenocarcinoma components, with the terminology updated from mixed adenoneuroendocrine carcinoma to MiNEN in the 2017 WHO classification (4). MiNEN is an extremely rare tumor with an annual incidence of less than 0.01 per 100,000 cases (5). GB is an uncommon site for primary NENs, comprising only 0.5% of all NEN cases (6). GB-NECs represent only 4% of all malignant GB tumors, and more than one-third of diagnosed GB-NECs exhibit adenocarcinoma components, thus classifying them as MiNENs (7). Currently, there are no established guidelines for the treatment of GB-MiNEN, and treatment approaches typically follow those for GB-NEC or GB-cancer.

In this case, NEC was diagnosed via FNA, thus leading to treatment initiation based on the NEC protocols. Standard chemotherapy regimens for advanced NEC commonly include EP and IP therapies, as demonstrated by the JCOG1213 (TOPIC-NEC) trial, which found no significant difference in overall survival (OS) between the EP and IP regimens in patients with advanced NEC of the digestive system (8). In this patient, we opted for IP therapy, which led to a substantial tumor reduction after five cycles, consistent with the reported 52.5% response rate for IP therapy in NEC (8). The suitability of conversion surgery remains controversial in MiNEN and NEC cases. Nandy et al. reported 124 GB-NEC and 19 GB-MiNEN cases, with a low median OS of 6.1 months; however, they reported that multimodal treatment, which included systemic therapy, chemoradiotherapy, and surgery, significantly improved OS. Patients who received multimodal treatment had a mean OS of 20.07 months, significantly longer than the 4.00 months observed in those who did not (9). Additionally, Song H's review of 767 MiNEN cases found that non-surgical treatment was an independent risk factor for poorer survival (10). In this case, after thorough consultation with the surgical team and the patient’s excellent performance status, conversion surgery was performed. Postoperative pathology confirmed the presence of both NEC and adenocarcinoma, establishing a diagnosis of MiNEN. Postoperatively, IP therapy was continued; however, owing to tolerance issues and the patient’s preference, S-1 monotherapy was administered. Unfortunately, recurrence was observed in the ureter 10 months later. In an analysis of 129 cases of distant metastases in gastroenteropancreatic MiNEN, 70.6% of the metastases were composed of the neuroendocrine component, 26.5% had coexisting neuroendocrine and adenocarcinoma components, and 2.9% were composed solely of the adenocarcinoma component, thus indicating that NEC components are more prone to metastasis. In this case, although a pathological evaluation of the recurrent lesion was not performed, CT findings of the recurrent ureteral tumor showed a round, expansively growing lesion, thus suggesting that the recurrent tumor may have predominantly consisted of NEC components (11). Recent studies have investigated second-line regimens such as nanoliposomal irinotecan/ 5-Fluorouracil and docetaxel, but no established regimens have demonstrated a clear survival benefit (12,13). In this case, after disease progression with IP therapy, we administered EP therapy, which is considered to be the standard first-line treatment for NEC. Unfortunately, the disease progressed in our case after three courses. Given the presence of the adenocarcinoma component, GCD therapy was administered. The TOPAZ-1 and KEYNOTE-966 trials have reported the efficacy of ICI plus GC therapy in GB-cancer, which has become a common first-line treatment (14,15). While the efficacy of ICI for GB-MiNEN or NEC remains unknown, long-term disease control was achieved in a MiNEN case with high PD-L1 expression when treated with PD-1 antibody combined with chemotherapy (16). However, in the present case, ICI treatment demonstrated only limited efficacy. Cancer genomic profiling testing revealed low microsatellite instability and low tumor mutational burden, suggesting that the effect of ICI on MiNEN may be limited. Recent studies, such as the NETTER-2 study, have reported the utility of peptide receptor radionuclide therapy (PRRT) in NET, including NET G3 (17,18). However, the efficacy of PRRT in NEC remains unclear. In this case, while SSTR2 staining in the surgical specimen suggested that PRRT could be effective, the lack of somatostatin receptor scintigraphy evaluation precluded consideration of this treatment. Future studies are therefore needed to clarify the therapeutic potential of PRRT in NEC.

Conclusion

The relatively favorable prognosis observed in this case suggests that a multimodal treatment strategy, including timely conversion surgery, may contribute to improved survival outcomes in cases with GB-MiNEN. Further case accumulation is essential to establish optimal treatment strategies, with timely consideration of conversion surgery likely to play a crucial role in prognosis extension. We hope that this report will aid in the future treatment of GB-MiNEN.

The authors state that they have no Conflict of Interest (COI).