Expression of brachyury in hemangioblastoma: potential use in differential diagnosis.

Hemangioblastoma (HBL) accounts for up to 2.5% of all intracranial tumors. It may occur as a sporadic entity or as a part of Von Hippel-Lindau syndrome. Patients with Von Hippel-Lindau syndrome are also at an increased risk of developing clear cell renal cell carcinoma (CCRCC). The distinction of HBL from CCRCC metastatic to the central nervous system (CNS) or from other histologic mimics can be challenging at times when based solely on hematoxylin and eosin-stained sections. In the present study we evaluated the potential use of the immunohistochemical evaluation of brachyury protein in the differential diagnosis of these lesions. Archival tissues from 22 HBLs, 16 primary CCRCCs, 8 CCRCCs metastatic to the CNS, and 4 angiomatous and 4 clear cell meningiomas were retrieved from our surgical pathology files and submitted to the immunohistochemical procedures against brachyury. Cases showing nuclear and/or cytoplasmic staining were considered to be positive for brachyury. Positive cytoplasmic staining was evidenced in the stromal cells of 20 of the 22 HBLs. In most cases, > 50% of the neoplastic cells were labeled, with strong or moderate intensity of staining. No nuclear or cytoplasmic staining for brachyury was observed in any of the primary renal or metastatic CCRCCs, nor in either of the meningioma types. Thus, brachyury cytoplasmic staining was demonstrated to be highly specific for HBL (specificity, 100%) and represented a sensible (sensitivity, 91%) method, with high positive (100%) and negative (89%) predictive values and high diagnostic accuracy (95%) in the differential diagnosis between HBL and CCRCC metastatic to the CNS or meningioma. On the basis of our findings we propose the use of brachyury as an additional helpful immunohistochemical marker to resolve the differential diagnosis of HBL toward histologic mimics.