Endocrine Abstracts

Introduction: Neuroendocrine tumors (NETs) are rare tumors harboring overexpression of somatostatin receptors (SSTRs) on their cell membrane. Gallium 68-tetraazacyclododecane tetraacetic acid-octreotate (68Ga-DOTATATE) positron emission tomography/computed tomography (PET/CT) is an important imaging modality in diagnosis and staging of NETs. Because some organs such as spleen, adrenal glands and liver physiologically express SSTR, it might be challenging to distinguish some pancreatic NETs located in the pancreatic tail from accessory spleen next to the splenic hilum. In this manuscript, we report a case with hypoglycemia attack and 2 different masses displayed by 68Ga-DOTATATE PET/CT.

Case report: A 63-year-old woman presented to the emergency with profuse sweating and light-headedness. Her blood glucose level was 45 mg/dl (2.5 mmol/l) and dextrose 5% infusion was started immediately. In the first hour after cessation of infusion, symptomatic hypoglycemia was developed with high insulin and C-peptide levels, 41 µIU/ml (1.9 – 23) and 12.7 ng/ml (0.9 – 7.1), respectively. The levels of antibodies to endogenous insulin were normal. Insulinoma was suspected and endoscopic ultrasonography (EUS) was planned, but it could not be performed. As a result, 68Ga-DOTATATE PET/CT was applied. It revealed two masses with increased tracer uptake located adjacent to the splenic hilum and inferior pole of the spleen which were reported as accessory spleens. 99mTc-labelled heat-denaturated red blood cell (99mTc-HDRBC) scintigraphy was applied to distinguish a NET in the pancreatic tail from accessory spleen at the splenic hilum. Enhanced tracer uptake remained in the inferior pole of spleen, but not in the splenic hilum. The lesions were suggestive of insulinoma in the pancreatic tail and an accessory spleen adjacent to the inferior pole of spleen. Hemipancreatectomy and splenectomy were performed. The histopathological findings revealed a grade 1 pancreatic neuroendocrine tumor.

Discussion: 99 mTc-HDRBC scintigraphy is a beneficial imaging method to display the functional splenic tissue. Therefore, it may be a reasonable imaging option to distinguish splenic tissue from NETs or their metastases. The basic mechanism of this imaging technique is based on denaturated red blood cell uptake by functioning spleen for the removal of abnormal erythrocytes. As described in our case report, 99 mTc-HDRBC scintigraphy is a useful nuclear medicine method to differentiate a NET in the pancreatic tail from accessory spleen at the splenic hilum. In conclusion, 99 mTc-HDRBC scintigraphy is a practicable specific diagnostic technique which may avoid unnecessary surgeries in the presence of enhanced tracer uptake or vice versa.