Low-Grade Clear Cell Renal Cell Carcinoma Mimicking Hemangioma of the Kidney A Series of 4 Cases

Context.-Clear cell renal cell carcinoma (CCRCC) has a rich, sinusoid-like vascularity frequently used as a diagnostic criterion. CCRCC with predominantly vascular architecture has not been described. Objective.-To describe 4 unusual CCRCC cases, primarily presenting with hemangioma-like morphologic pattern. Design.-Clinicopathologic and selected immunohistochemical analysis of 4 cases of CCRCC mimicking hemangioma. Results.-Cases were seen in 1 woman and 3 men (average age, 48.8 years; range, 40-66 years). Grossly, tumors were red-brown (3 of 4) with scant bright-yellow foci in 1. The average tumor size was 4 cm (range, 2.5-5.5 cm). Microscopically, all were composed of varying proportions of a rich, arborizing, sinusoid-like vasculature with focal hobnail appearance of endothelial cells. Entrapment of renal tubules between blood vessels was seen at the periphery of the tumors. This morphology was reminiscent of anastomosing hemangioma. Isolated tumor cells resembling lymphocytes with clear halos were sparsely interspersed between vessels. Cytokeratin immunostain confirmed the diagnosis of CCRCC. Conclusion.-Extensive sampling and immunohistochemical workup of what is deemed to be a benign vascular neoplasm of the kidney is needed to rule out the presence of individual carcinoma cells or small viable carcinoma cell clusters.