Unusual immunohistochemical profiles in hemangioblastomas and their relevance in differential diagnosis: A comprehensive study of 112 cases.

Hemangioblastomas (HB) are rare CNS neoplasms. Their main differential diagnosis includes meningioma, glioma, and metastatic clear cell renal carcinoma. However, the diagnostic immunoprofile of HBs is only imprecisely defined. We analyzed a multicentric cohort of HBs using tissue microarrays and whole sections to determine immunoreactivities of a range of selected meningothelial, glial and other markers used in diagnostic pathology. The clinical and pathological features were correlated. The cohort included 112 tumors from 104 patients (46.1% males, 53.9% females) with a mean age 50.1 years. The tumors occurred in cerebellum (72%), spine (18.9%) and medulla oblongata (5.4%). No HB expressed SSTR2A, MUC4 or STAT6. Expression of glial markers S100, GFAP, Olig2, and SOX10 was observed in 93.3%, 80.6%, 5.1%, and 8.1% of cases, respectively. Inhibin-α was positive in 84.5% and carbonic anhydrase IX (CAIX) in 100% of the cases. Negative PAX8 immunostaining was observed using specific C-terminus antibody whereas N-terminus anti-PAX8 staining yielded 63.2% positivity. T-brachyury, SATB2, and GPNMB were observed in 3.8%, 2.1%, and 20.8%, respectively. No expression of SOX17, CDX2, Sall4, GATA3, or INSM1 was observed. Thus, HBs show a consistent PAX8-negative/CAIX-positive immunoprofile while they lack meningothelial markers and occasionally may express SOX10 and Olig2.