A case of gallbladder neuroendocrine carcinoma diagnosed preoperatively using somatostatin receptor scintigraphy.

Gallbladder neuroendocrine carcinoma (NEC) is a rare gallbladder tumor. The current report is a case of a patient preoperatively diagnosed with gallbladder NEC using somatostatin receptor scintigraphy (SRS). A 63-year-old man was admitted to our hospital by a family doctor after abdominal ultrasonography revealed thickened walls of the neck of his gallbladder. At Kagoshima University Hospital, CT and MRI of the abdomen and endoscopic ultrasonography confirmed the thickening of the walls of the neck of the gallbladder. However, it did not resemble a typical gallbladder cancer or tumor, such as a neuroendocrine tumor or malignant lymphoma. Positron emission tomography and SRS showed abnormal accumulation at the tumor site. Endoscopic retrograde cholangiopancreatography was performed, adenocarcinoma was suspected based on intra-gallbladder bile cytology, and a cholecystectomy with lymphadenectomy was performed. The postoperative pathological diagnosis was small cell NEC (pT3a, N0, M0, stage II). Immunohistochemistry indicated that the gallbladder tumor cells were positive for synaptophysin, chromogranin A, and cluster of differentiation (CD) 56, and negative for somatostatin receptors (SSTR) 2 and 5. Gene expression assays revealed the expression of all SSTR subtypes (SSTR1-5) in the tumor. Generally, NECs exhibit poor accumulation in SRS, however, the results of the current case suggest that SRS may be useful in the preoperative diagnosis of NEC.