Frequent expression of somatostatin receptor 2a in olfactory neuroblastomas: a new and distinctive feature

Olfactory neuroblastoma (ONB) is a malignant neuroendocrine neoplasm with a usually slow course, but with considerable recurrence rate. Many neuroendocrine tumors have shown good response to the treatment with somatostatin analogs and somatostatin radioreceptor therapy. In ONBs, there are scarce data on somatostatin-based treatment and the cellular expression of somatostatin receptors (SSTR), the prerequisite for binding and effect of somatostatin on normal and tumor cells. The aim of our study was to investigate the immunohistochemical expression of SSTR2A and SSTR5 in a cohort of 40 ONBs. In addition, tissue microarrays containing 40 high-grade sinonasal carcinomas as well as 6 sinonasal lymphomas, 3 rhabdomyosarcomas, and 3 Ewing sarcomas were evaluated. Volante system was applied for staining evaluation. Thirty cases (75%) were immunopositive for SSTR2A and 3 (7.5%) for SSTR5. Among the 30 SSTR2A-positive ONBs, 19 tumors (63.3%) scored 2+ and 11 (36.7%) scored 3+. All SSTR5-positive ONBs scored 2+. Neither sinonasal carcinomas nor sinonasal small round blue cell neoplasms expressed SSTR2A or SSTR5. The frequent expression of SSTR2A provides a rationale for radioreceptor diagnosis and therapy with SST analogs in ONBs. SSTR2A expression in ONBs is a helpful adjunct in the differential diagnosis of ONBs.