Renal angiomyolipoma: evolutional changes of its internal structure on CT.
BACKGROUND: We evaluated interval changes of the internal structure of renal angiomyolipomas in relation to the doubling time on computed tomography (CT). METHODS: A retrospective review of 42 renal angiomyolipomas in 10 patients who had been followed up for more than 5 months with CT was performed. The doubling time of each tumor was estimated. We classified the internal structures of the tumors into five types, based on the fat component percentage. We compared changes between initial and follow-up CT, and the relationship with the doubling time was evaluated. RESULTS: The fat component increased more than the soft tissue component in 15 tumors (36%). The soft tissue component increased more than the fat component in only one tumor, in which an intratumoral hemorrhage occurred during the follow-up period. Twenty-six tumors (62%) showed no change. Most tumors with relatively long doubling times did not show a change in their internal structures. CONCLUSION: The growth of renal angiomyolipoma is due mainly to an increase in its fat component. An increase in the soft tissue component suggests the development of an intratumoral hemorrhage.