RESUMO
We present a rare case of renal angioleiomyoma with rapid growing during one-year and seven-months' follow-up. The CT findings correlated well with the histopathological findings. The patient was a 62-year-old man with right renal mass that was incidentally found on CT. The first CT showed a solitary mass lesion that was 2.0 cm in diameter with a well-defined margin at the right renal medulla. It was gradually enhanced on contrast-enhanced CT. Follow-up CT was performed after one year and seven months, and the mass had grown to 3.8 cm in diameter and showed heterogeneous density on unenhanced CT. The mass had an early enhanced area in the corticomedullary phase, and this enhancement lasted into the nephrographic phase. Another area was gradually enhanced heterogeneously. Right radical nephrectomy was performed, and the histopathological diagnosis was renal angioleiomyoma. The early enhanced area of the mass corresponded to large vessels filled with blood, and the other area was mainly composed of bundles of smooth muscle, fibrous tissue, and minute blood vessels. It is important to know that the CT findings of real angioleiomyoma may show hypervascularity but are atypical for renal cell carcinoma (RCC), and a tendency for growth may be present.