Differential Diagnosis of Meningeal SFT-HPC and Meningioma: Which Immunohistochemical Markers Should Be Used?

Meningeal solitary fibrous tumors-hemangiopericytomas (SFT-HPC) and meningiomas can be difficult to distinguish on histologic examination. STAT6 immunohistochemistry (IHC) is a reliable diagnostic marker of SFT-HPCs. Recently, GRIA2 has also been reported to be a diagnostic marker of SFT-HPC, although no extensive data are available for meningeal SFT-HPCs yet. The aim of this study was to test their diagnostic performance in a large cohort of SFT-HPCs and meningiomas. IHC analyses for GRIA2 and STAT6 were performed on tissue microarrays containing 76 SFT-HPCs and 181 meningiomas. Results were compared with previous data with ALDH1 and CD34. Two different anti-STAT6 antibodies were tested: SC-20 polyclonal and YE361 monoclonal antibody. Ninety-six percent of meningeal SFT-HPCs but no meningioma displayed nuclear STAT6 positivity. With SC-20 antibody, concomitant cytoplasmic staining for STAT6 was observed in >50% of all cases, including meningiomas. However, using YE361 antibody, cytoplasmic staining was absent, and nuclear signal intensity was stronger leading to better interpretation of STAT6 IHC. GRIA2 was positive in 84% of SFT-HPCs and in 16% of meningiomas. STAT6 had excellent sensitivity (96%) and specificity (100%), ALDH1 and GRIA2 had same sensitivity (84%), but ALDH1 and CD34 had better specificity than GRIA2 (97% and 96% vs. 84%, respectively). For the differential diagnosis of SFT-HPCs versus meningiomas, the best diagnostic approach is to perform STAT6, followed by ALDH1 and CD34 in the case of uncommon STAT6-negative cases. Because of meningioma positivity, GRIA2 seems less useful in this indication.

Histopathologic and ultrastructural features and claudin expression in papillary tumors of the pineal region: a multicenter analysis.

Neuroepithelial papillary tumor of the pineal region (PTPR) has been defined as a distinct entity that is increasingly being recognized, with 96 cases now reported. This tumor shares morphologic features with both ependymomas and choroid plexus tumors. PTPR is characterized by an epithelial-like growth pattern in which the vessels are covered by layers of tumor cells forming perivascular pseudorosettes. These tumors exhibit various combinations of papillary and solid architecture, making the differential diagnosis of PTPR difficult to establish. We report the detailed description of the histopathologic features of a large series of PTPRs from 20 different centers and distinguish 2 subgroups of tumors with either a striking papillary growth pattern or a papillary and solid growth pattern. We highlight the findings that PTPRs have unusual vessels with multiple lumina and frequently show detachment of the border of the tumoral cells from the vascular wall. The 2 PTPR subgroups present similar clinical characteristics and immunophenotypes. We confirmed and extended the results of previous ultrastructural studies on the presence of intercellular junctions at the apical part of tumoral cells. The expression of the tight junction proteins claudin-1, claudin-2, and claudin-3 was investigated by immunohistochemistry. Claudin-1 and claudin-3, but not claudin-2, were expressed in PTPRs and in the fetal subcommissural organ, potentially the origin of this tumor. In contrast, all 3 claudins were expressed in choroid plexus papillomas. Claudin expression may help in the diagnosis of PTPRs and can be used in combination with other markers, such as CK18, NCAM, E-cadherin, MAP-2, and Kir 7.1.