Detection of Abdominal Lymph Node Metastasis from Pancreatic Neuroendocrine Tumor by Somatostatin Receptor Scintigraphy: Comparison with Somatostatin Receptor Type 2 Immunostaining.

We report a 58-year-old male with a histopathologically proven grade 2 (G2) pancreatic neuroendocrine neoplasm and multiple abdominal node metastases by use of a laparoscopic pancreatic body and tail resection procedure, plus abdominal lymph node dissection. A primary pancreatic tail neuroendocrine tumor sized 20 × 25 mm was detected by contrast-enhanced computed tomography, somatostatin receptor scintigraphy (SRS), and fluorodeoxyglucose positron emission tomography (FDG-PET) examinations and pathologically diagnosed as a pancreatic neuroendocrine tumor (PNET, G2) based on positive immunostaining for somatostatin receptor (SSTR) type 2. Of three metastatic histopathological lymph nodes, two measured 18 × 21 and 10 × 12 mm, respectively, with whole strong SSTR immunostaining showing moderate uptake in SRS findings, whereas the other node, sized 8 × 10 mm, had strong SSTR immunostaining only in a small 6 × 6-mm-sized portion and showed no uptake in SRS findings, likely because of the limited spatial resolution of scintigraphy. On the other hand, only the largest node (18 × 21 mm) was visualized by FDG-PET. SRS may be useful for metastatic lymph node diagnosis based on SSTR immunostaining, though a disadvantage is the spatial resolution limitation.