Unclassified hemangioma-like renal cell carcinoma: a potential diagnostic pitfall

Recently, rare renal cell carcinomas (RCCs) have been reported to closely mimic hemangioma; however, these have been largely recognizable as clear cell RCC. Conversely, true hemangiomas of the kidney are also increasingly recognized. We report a 62-year-old woman who underwent partial nephrectomy for a hemangioma-like RCC without appreciable clear cell morphology. Immunohistochemistry revealed luminal structures that stained positively for cytokeratin, cytokeratin 7, carbonic anhydrase IX, PAX8, and high-molecular-weight keratin, admixed with a CD34-positive, CD31-positive, and ERG-positive complex network of vessels. Staining was minimal for α-methyl-acyl-coA-racemase and EMA, and absent for GATA3, HMB45, melan-A, and cathepsin K. Fluorescence in situ hybridization revealed no TFE3 or TFEB rearrangement, 3p deletion, or trisomy 7 or 17. This case adds to the spectrum of hemangioma-like RCC with differing morphology and immunophenotype. Further study will determine whether this represents a distinct entity or an unusual pattern of degenerative changes in an existing entity.