Immunohistochemical determination of somatostatin receptor subtypes 1, 2A, 3, 4, and 5 in various adrenal tumors

While octreotide binds with high affinity to sst2a only, the new analogue SOM230 demonstrates high affinity for sst1, 3, and 5, in addition. We examined the immunohistochemical expression of somatostatin receptor subtypes (sst) in 7 pheochromocytomas (PHEO), 5 Conn adenomas (CONN), 9 Cushing adenomas (CUSH), 7 nonfunctioning tumors (NFA), and 4 adrenal carcinomas (CA). About one third of the PHEO were positive for sst1, 2a, and 5. Less than 30% of cells were stained in the majority of these tumors. Each of the PHEO expressed sst3 with more than 60% of cells stained. Two thirds of the NFA revealed positive staining for sst1, 2a, and 3 with less than 30% of cells affected. Sst5 was expressed in nearly all of the NFA with positive staining in 30-60% of tumor cells. Nearly all CUSH and CONN were positive for the subtypes evaluated. In the majority of these tumors, less than 30% of cells were positively stained. Fifty percent of CA expressed sst2a and 3 with positive staining in 30- 100% of cells. None of them expressed sst1. Somatostatin receptors are expressed in adrenal tumors with a tumor-specific distribution pattern. This may offer new diagnostic and therapeutic possibilities.