Gallbladder Mixed Neuroendocrine-Non-Neuroendocrine Neoplasm Consisting of Adenocarcinoma and Neuroendocrine Tumor G2 Diagnosed after Surgery for Acute Cholecystitis: A Case Report and Exome Analysis

Abstract

Introduction: Among neuroendocrine neoplasms (NENs), non-neuroendocrine and NEN components may rarely coexist, which are referred to as mixed neuroendocrine-non-NENs (MiNENs). Most gallbladder MiNENs are progressive and associated with neuroendocrine carcinoma (NEC), but rarely with neuroendocrine tumor (NET) as a component. To our knowledge, there are 4 reported cases of mixed gallbladder tumors with NET as a component. From the genetic analysis of MiNENs consisting of NEC, MiNEN is believed to have a common origin, as each tumor component shares a common TP53 mutation. Our case is an extremely rare reported case of a mixed gallbladder tumor with a NET component as a MiNEN, and the first reported case of whole-exome analysis performed on a resected specimen.

Case presentation: A 77-year-old woman presented to our hospital with epigastric pain. An emergency laparoscopic cholecystectomy was performed with a diagnosis of acute gallstone cholecystitis. Pathological examination revealed gallbladder MiNEN (adenocarcinoma + NET G2). Additional surgery was performed, but no residual tumor was found. The patient has been recurrence-free for 36 months after surgery without adjuvant therapy. The origin of the tumor was examined. Macroscopically, adenocarcinoma cells were present on both sides of the NET, while microscopically, some adenocarcinoma cells were positive for neuroendocrine markers (synaptophysin and chromogranin A). Staining for p53 showed wild-type staining with scattered, weakly expressing cells in both tumors. Subsequently, we performed whole-exome sequencing of each tumor component. The results showed that each tumor component shared TP53 c.1015G>T (p.Glu339Ter), ERBB3 c.889G>A (p.Asp297Asn), and CDKN2A c.416G>A (p.Gly139Asp) mutations, suggesting that the adenocarcinoma might have differentiated into NET G2.

Conclusions: In this case report, the tumors shared a common genetic mutation, suggesting that MiNENs with NET components may share a common origin. Furthermore, the NEN component of MiNEN occurring in the gallbladder was associated with a TP53 mutation, despite the low frequency of TP53 mutations in normal NETs.

Keywords: acute cholecystitis; gallbladder cancer; mixed neuroendocrine–non-neuroendocrine neoplasms (MiNENs).

Fig. 1. Computed tomography findings. (A) Multiple incarcerated gallstones (yellow arrow) are observed. (B) Swelling of the gallbladder and edematous circumferential thickening of the gallbladder wall are observed.

Fig. 2. Magnetic resonance imaging findings. (A) A Rokitansky–Aschoff sinus is observed, and gallbladder adenomyomatosis is suspected. (B) Diffusion-weighted imaging shows nodular thickening of the fundus of the gallbladder with restricted diffusion (yellow arrow).

Fig. 3. Macroscopic findings of the resected specimen. (A, B) Adenocarcinoma is in close proximity to the edge of the cystic duct (yellow arrow).

NET, neuroendocrine tumor

Fig. 4. Histopathologic and immunohistochemical findings. (A) The borderline between adenocarcinoma and neuroendocrine tumor at low magnification (H&E staining, ×100). The red dotted line is the border; above the line is the neuroendocrine tumor, and below the line is adenocarcinoma. (B) Areas with multiple mitotic figures in the neuroendocrine tumor. Tumor cells with a high nucleo-cytoplasmic ratio and rough chromatin form nests, cords, and ribbons and invade. Two mitotic figures are observed in a high-power field (arrow) (H&E staining, ×400). (C, D) The neuroendocrine tumor and some of the adenocarcinoma cells are positive for chromogranin A (C: ×100; D: ×400). (E, F) The neuroendocrine tumor and some of the adenocarcinoma cells are positive for synaptophysin (E: ×100; F: ×400). (G) Ki-67 staining of the NET G2. The percentage of cells expressing Ki-67 is 70/500 (positive cells/total cells), 14% (×400). (H) Ki-67 staining of adenocarcinoma. The percentage of cells expressing Ki-67 is 230/500 (positive cells/total cells), 46% (×400).

H&E, hematoxylin and eosin; NET, neuroendocrine tumor

Fig. 5. Illustration of the TP53, ERBB3, and CDK2NA gene alterations in each tumor component. WES data, visualized using Integrative Genomics Viewer software, reveal identical TP53 c.1015G>T (p.Glu339Ter), ERBB3 c.889G>A (p.Asp297Asn), and CDKN2A c.416G>A (p.Gly139Asp) mutations in each tumor component.

NET, neuroendocrine tumor; WES, whole-exome sequencing

Fig. 6. Immunohistochemical findings. (A) Rb1 staining in adenocarcinoma. Rb1 expression is observed in the nuclei of tumor cells (×400). (B) Rb1 staining in NET G2. Rb1 expression is observed in the nuclei of tumor cells (×400). (C) p53 staining in adenocarcinoma. Tumor cells show weak and scattered p53 expression (usual pattern) (×400). (D) p53 staining in NET G2. Similar to adenocarcinoma, the tumor cells show weak and scattered p53 expression (usual pattern) (×400).

NET, neuroendocrine tumor