Sporadic hemangioblastoma of the kidney: an underrecognized pseudomalignant tumor?

Hemangioblastoma is a benign tumor that can occur sporadically, or in association with von Hippel-Lindau disease in approximately one-quarter of the cases. Only exceptionally does it occur outside the central nervous system. This report describes 2 cases of sporadic renal hemangioblastoma, with 1 patient presenting with hematuria and polycythemia, and the other low back pain. Histologically, the tumors were circumscribed, and composed of sheets of large polygonal cells traversed by arborizing thin-walled blood vessels. Many of the tumor cells showed pleomorphic nuclei, but the mitotic figures were rare. The cytoplasm was eosinophilic, and occasionally finely vacuolated indicating the presence of lipid. The diagnosis of hemangioblastoma was confirmed by negative immunostaining for cytokeratin, and positive staining for α-inhibin, S100, and neuron-specific enolase. This benign neoplasm which can be mistaken for various malignancies such as renal cell carcinoma, epithelioid angiomyolipoma, adrenal cortical carcinoma, and paraganglioma, deserves wider recognition for its occurrence as a primary renal tumor.