Sstr2A immunohistochemical expression in human meningiomas: is there a correlation with the histological grade, proliferation or microvessel density?

Somatostatin anti-proliferative and anti-angiogenic activities, together with the expression of somatostatin receptors (sstrs), account for the use of somatostatin analogues in the treatment of human tumours. In the present study, sstr2A immunohistochemical expression was analyzed in grade II and III meningiomas and was compared with that revealed in grade I meningiomas. Thirty-five formalin-fixed paraffin-embedded meningiomas, comprising 13 grade I, 19 grade II and 3 grade III tumours, according to the WHO 2007 classification, were submitted to immunohistochemical assays for sstr2A. Moreover, in the same cohort of tumours, the immunoexpression of CD105, a specific marker for neo-angiogenesis, as well as the Ki-67 labelling index (LI), reflecting the proliferative activity of the meningiomas, were recorded. Sstr2A immunoreaction was evidenced in 26/35 cases and was localized at the cytoplasm and the plasma membrane in 12 and in 14 cases, respectively. Specifically, a positive staining was found in 7/13 grade I, in 16/19 grade II and in 3/3 grade III tumours, thus demonstrating that sstr2A is frequently expressed in high grade meningiomas. A significantly higher microvessel density (MVD), assessed by CD105 immunostaining and Ki-67 LI were evidenced in high grade meningiomas. A significant correlation was recorded between sstr2A expression and a high MVD of the meningiomas. The existence of a correlation between sstr2A expression and the entity of neo-angiogenesis provides the basis for the use of somatostatin analogue-based therapies in the treatment of meningiomas.