Immunocytochemical staining for human chorionic gonadotropin subunits does not predict malignancy in insulinomas

Insulinomas, the most common pancreatic endocrine tumors, produce a clinical syndrome of hyperinsulinism and hypoglycemia. Although the majority of insulinomas are benign, a significant proportion (4-16%) behave aggressively. Because malignant potential cannot be assessed adequately by histopathologic criteria, reliable serum and immunocytochemical markers for malignancy have been sought. Recent reports suggest that subunits of human chorionic gonadotropin (hCG) are of prognostic value in pancreatic endocrine tumors. Elevated serum levels of either the alpha-subunit or beta-subunit of hCG have been reported to be associated with malignancy in pancreatic endocrine tumors. Both hCG and its alpha-subunit have been demonstrated in malignant pancreatic endocrine tumors by immunohistochemistry. In this study, 17 insulinomas have been analyzed by immunohistochemistry using monospecific antibodies to both the alpha-subunit and beta-subunit of hCG. Clinical follow-up was obtained in all cases, and four of the tumors proved to be malignant. Alpha-subunit immunoreactivity was found in only two tumors, both of which were benign. Immunoreactivity for the beta-subunit was not found in any tumor. The authors' results indicate that for this subset of pancreatic endocrine tumors, staining for hCG subunits is of no value in predicting malignant behavior.