Primary hemangioblastoma of the kidney with molecular analyses by next generation sequencing: a case report and review of the literature.

BACKGROUND: Hemangioblastoma is an indolent mesenchymal tumor most frequently occurring in the central nervous system (CNS), but can also arise extraneuraxially, as part of Von Hippel-Lindau (VHL) disease or in sporadic tumors. Extraneuraxial hemangioblastomas occur outside the central nervous system. It includes tumors arising from the nervous paraneuraxial structures and visceral organs. Sporadic hemangioblastoma of the kidney, a rare subset of extraneuraxial hemangioblastomas, is an under-recognized renal neoplasm. There have been only 25 cases described to date in the English language literature. We report herein one additional sporadic tumor in a patient without VHL disease.

CASE PRESENTATION: A 61 year old male presenting with gross hematuria was found to have a 3.5 cm renal mass at the lateral mid to lower pole of the left kidney on computed tomography urogram. The patient underwent a partial nephrectomy for the mass. Pathological examination showed a well-circumscribed non-encapsulated tumor composed of sheets of large polygonal cells traversed by a rich vascular network. The tumor cells showed clear to eosinophilic cytoplasm and overall bland nuclei. The diagnosis of hemangioblastoma was confirmed by positive immunostaining for alpha-inhibin, S100, neuron-specific enolase, and PAX8. No significant gene mutations, including VHL gene and copy number changes were detected in the tumor using next generation sequencing supporting the diagnosis of sporadic renal hemangioblastoma.

CONCLUSION: Sporadic renal hemangioblastoma is a rare subset of extraneuraxial hemangioblastomas. We report one such tumor in a patient without clinical or molecular evidence of VHL disease. The literature was reviewed to better understand the clinical, radiological, pathological, and molecular features of this neoplasm. The majority of renal hemangioblastomas showed positive immunostaining for PAX8, which supports the idea that the immunoprofiles of extraneuraxial hemangioblastomas can vary depending on sites of origin. Diagnosis of renal hemangioblastoma is challenging because of its rarity and overlapping microscopic and immunophenotypic features with other renal tumors, including clear cell renal cell carcinoma. In some cases, molecular or genetic studies may be necessary to obtain an accurate diagnosis. Since renal hemangioblastoma is clinically benign, recognition of this pathological entity is important to avoid unnecessary over-treatment.