Polypoid gallbladder neuroendocrine tumor diagnosed as benign polyp before surgery: A case report

Abstract

Gallbladder neuroendocrine tumors (GB-NETs) comprise only 0.5% of all NET cases, and their biology has been incompletely characterized. In the present study we report the case of a 50-year-old male patient with GB-NET who was admitted to Naito Hospital with diarrhea as the main complaint. At initial diagnosis, serum carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) levels were within the normal range. Abdominal ultrasonography and contrast-enhanced computed tomography (CT) revealed gallbladder adenomyomatosis and cholecystitis, and an 8-mm pedunculated polypoid lesion was found in the neck of the gallbladder using drip infusion cholecystocholangiography-CT. As it was considered a benign polyp, laparoscopic cholecystectomy was performed. Pathological examination revealed a polypoid lesion that comprised NET cells with a cord-like or ribbon-like arrangement, and the cells exhibited positive immunostaining for chromogranin A and synaptophysin. In addition, immunohistochemical staining showed a Ki-67 index (i.e., proliferation index) of <1%, and no necrosis or mitotic figures were observed in the background. Based on these observations, we diagnosed the following: GB-NET, G1, 10x12 mm in size and located in the gallbladder neck. According to the World Health Organization 2010 classification, NET G1 is a well-differentiated tumor, with the tumor cells having a low proliferative potential [Ki-67 index ≤2%; mitotic figure number <2 (/10 HPF)]. It is regarded as a low-to mild-grade malignancy. Low-grade GB-NET occurs relatively rarely, and no clear guidelines have been formulated regarding its surgical treatment, such as minimal surgical excision margins or lymph node dissection. Detailed treatment recommendations should be developed after systematic studies of additional cases of GB-NET.

Neuroendocrine tumors of the gallbladder (Review)

“…A NEN originates and spreads from neuroendocrine cells and peptidergic neural crest Kulchitsky cells (silver-addicted cells) (1). These cells perform essential biochemical functions such as the uptake of amine precursors, decarboxylation, and the release of bioactive peptide hormones and nerve mediators (2). As the occurrence of gallbladder NEN (GB-NEN) is low, it is difficult to obtain clear and large amounts of data on the etiology, pathogenesis, standard treatment plan and prognosis from large-scale studies conducted at multi-center research centers.…”

Clear cell neuroendocrine tumor in the gallbladder diagnosed as a benign polyp preoperatively: a case report

“…Although 61.5% of gallbladder NETs in the neck are pedunculated, 38.5% of gallbladder NETs in the neck and all gallbladder NETs in the body and fundus are not pedunculated [ 10 ]. Almost all gallbladder NEN patients are asymptomatic, and the proportion of hormone-producing gallbladder NENs is unknown because of the small number of reported cases [ 11 ]. Regarding clear cell gallbladder NET, most cases were in the neck of the gallbladder and pedunculated, and all cases were surgically resected by laparoscopic cholecystectomy.…”

“…Previous research recommends that local excision without lymphadenectomy should be carried out for NET G1 tumors less than 2 cm in the stomach, duodenum, appendix, and rectum. Lymphadenectomy is recommended for other gastroenteropancreatic NENs in the jejunum, ileum, colon, and pancreas [ 9 , 11 ]. Although the risk of metastasis depends on the tumor size in several gastroenteropancreatic NENs, the risk factors for metastasis of gallbladder NEN have not been clarified because only a small number of cases have been reported [ 11 ].…”

“…Lymphadenectomy is recommended for other gastroenteropancreatic NENs in the jejunum, ileum, colon, and pancreas [ 9 , 11 ]. Although the risk of metastasis depends on the tumor size in several gastroenteropancreatic NENs, the risk factors for metastasis of gallbladder NEN have not been clarified because only a small number of cases have been reported [ 11 ]. Previous NET research reported that the frequency of metastases was two of seven cases (28.6%) for tumors less than 1 cm, while all five cases with tumors measuring 3 cm or more had metastases.…”

Mixed Intraepithelial Neoplasia—Well-Differentiated Neuroendocrine Tumor of the Gallbladder: A Hitherto Unreported Combination

“…The majority of gallbladder NENs are represented by poorly differentiated NENs/NECs, while well-differentiated NENs/NETs are extremely rare in this location. 8,9 Occasionally, gallbladder NENs may present as a part of a mixed neoplasm harboring also a non-neuroendocrine component. Most published cases of biliary MiNENs represent MANECs.…”