[1725] Somatostatin Receptor 2A: A Novel Immunohistochemical Marker of Meningioma

Carlos E Bacchi, Patty L Kandalaft, Harry C Hwang, Lynn C Goldstein, Lisandro L Lopes, Livia M Bacchi, Allen M Gown. PhenoPath Laboratories, Seattle, WA; Consultoria em Patologia, Botucatu, SP, Brazil

Background: Meningiomas account for approximately one quarter of primary intracranial tumors, and while they generally display characteristic histologic features, there is some overlap with other tumors, such as schwannomas, hemangiopericytoma/solitary fibrous tumors, and gliomas. While epithelial membrane antigen (EMA), progesterone receptor (PR), CD99, bcl-2, and claudin-1 have been considered immunohistochemical markers of meningiomas, the reported sensitivities and specificities of these markers are not optimal. Based upon previously reported findings in a small number of cases, we wished to test the hypothesis that SST2A could prove to be a highy sensitive and specific marker of meningioma.
Design: 27 cases of meningiomas and 21 cases of schannomas, hemangiopericytoma/solitary fibrous tumors, or gliomas were obtained from the files of PhenoPath Laboratories and Consultoria em Pathologia. Deparaffinized, formalin fixed tissues were incubated with antibodies to SST2A [rabbit monoclonal antibody UMB1 (Epitomics, Burlingame, CA) with localization by the Quanto polymer based detection system (ThermoFisher, Waltham, MA)]. A semiquantitative scoring system was employed based upon the fraction of tumor cells showing positivity (low, <25% of tumor cells positive; intermediate, 26-75% of tumor cells positive; high, >75% of tumor cells positive).
Results: 27/27 (100%) of meningiomas were positive for expression of SST2A, virtually all of them strong and uniform (nearly 100% of tumor cells positive). In contrast, 2/21 non-meningiomas (both hemangiopericytoma/solitary fibrous tumors) demonstrated positivity, albeit focal. Thus, the sensitivity of SST2A for meningiomas was 100% with 90% specificity, based upon the limited tissues studied.
Conclusions: SST2A is one of two isoforms of the somatostatin 2 receptor, which in turn is one of five subtypes of somatostatin receptors. SST2A has been previously demonstrated to localize to neuroendocrine tumors, and has also been used as an immunohistochemical tissue correlate of in vitro I-[Tyr]-octreotide autoradiography. This study demonstrates an additional potential utility for SST2A, as we have demonstrated exceedingly high sensitivity and specificity for meningiomas in comparison to other tumors for which there can be histologic overlap. Further studies are warranted to see if this high sensitivity and specificity can be documented in a larger series of tumors, as well as many of the morphologic variants of meningiomas.
Category: Neuropathology

Monday, March 4, 2013 9:15 AM

Proffered Papers: Section G1, Monday Morning

 

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