Objectives: Pancreatic neuroendocrine tumors (PNETs) are known to have heterogeneity in terms of their ability to produce multiple hormones. The aim of this study was to evaluate the heterogeneity of PNETs from the viewpoint of hormonal expression.
Methods: The expressions of 4 representative hormones, gastrin, insulin, glucagon, and somatostatin, in both primary and metastatic lesions, were analyzed by immunohistochemical staining in 20 patients with metastatic PNETs (6 gastrinomas, 1 insulinoma, 1 glucagonoma, and 12 nonfunctioning PNETs [NF-PNETs]). Metastatic sites included lymph nodes in all 20 patients and liver metastasis in 7 patients (2 gastrinomas and 5 NF-PNETs).
Results: There were 6 PNETs with multiple hormone secretion (30%), and positive expression of 1 or more hormones was found in 9 of 12 patients whose primary tumors were diagnosed as NF-PNETs. The positive concordance rate of the hormonal expression pattern between primary tumors and metastatic lymph nodes and between primary tumors and hepatic metastasis were 50% and 11%, respectively. Three patients had metastatic lesions with positive hormonal expression, whereas their primary tumors were negative.
Conclusions: Hormonal expressions are often different between the primary tumors and metastatic sites of PNETs.