Growth rates of renal cell carcinoma and oncocytoma under surveillance are similar

ObjectiveThrough examining our experience with renal mass surveillance, we hoped to determine factors suggestive of renal cell carcinoma.MethodsWe followed for at least 1 year 41 patients with 47 solid renal masses (mean diameter 2.0 cm, range 0.8–5). Mean surveillance duration was 29 months and was more than 2 years for 23 masses (49%).ResultsOverall mean increase in diameter was 0.27 cm/year, but 21 (45%) did not grow, and mean growth rate was 0.5 cm/year in the 26 that did grow. Of the masses, 14 have been treated, 33 continue to be followed, and pathology is known in 16 (34%). Growth was seen in all 6 known oncocytomas (mean 0.52 cm/year), 80% of the 10 biopsy proven renal cell carcinomas grew (mean 0.71 cm/year), but only 12 (39%) of the masses with unknown pathology (0.08 cm/year). There was no factor that distinguished oncocytomas from renal cell carcinomas. In 1 patient, a 3-cm mass that had not changed in size for 6 years doubled in size over 6 months, and metastatic disease developed.ConclusionsAlthough growth of most renal masses is slow, some grow quickly, and delayed growth with metastases can occur. No factor distinguished renal cell carcinomas from oncocytomas. Surveillance for renal masses remains an option but must be rigorous and continuous, and is not without risk of progression.