Renal hemangioblastoma and renal cell carcinoma with fibromyomatous stroma and hemangioblastoma-like areas belong to the spectrum of one entity.

Several reports have documented renal cell carcinomas (RCC) with fibromyomatous stroma and with areas of hemangioblastoma (RCC FMS-HB). The hemangioblastoma component in RCC FMS-HB tumors was similar to the morphology of primary renal hemangioblastoma, suggesting that RCC FMS-HB and renal hemangioblastoma share common features. Seven study cases were collected, comprised of three RCC FMS-HB (two sporadic and one in a tuberous sclerosis patient) and four pure renal hemangioblastomas. A molecular analysis was successful in 6/7 cases. There were four males and three females, with an age range of 27 to 74 years, and a mean age of 51 years. The tumors measured from 2.6 to 5.5 cm (median 3.5 cm), and all were organ-confined, stage pT1. Median size for RCC FMS-HB was 2.8 cm, and for renal hemangioblastoma, it was 3.5 cm. The hemangioblastoma component in all RCC FMS-HBs and in all renal hemangioblastomas was positive for inhibin-α and S100 but was negative for CK7. In contrast, the clear-cell epithelial component in RCC FMS-HB was diffusely reactive for CK7 and was negative for inhibin-α and S100. Both components were reactive for CAIX, vimentin, and GPNMB. TSC/MTOR pathway alterations were found in 6/6 successfully evaluated cases, including 3/3 RCC FMS-HB and 3/3 renal hemangioblastomas, with mutations in TSC1 (2/6), TSC2 (2/6), and MTOR (2/6). The shared morphologic, immunohistochemical, and molecular features of RCC FMS-HB and renal hemangioblastoma indicate that they belong to a common biological spectrum, and that renal HB is a distinct entity from its VHL-altered central nervous system counterpart.