Small renal neoplasms: diagnostic imaging, pathologic features, and clinical course.

We retrospectively studied nine patients with solitary renal neoplasms that were first visible when smaller than 3 cm in diameter to determine their imaging and pathologic characteristics and clinical course. These neoplasms represented 14% of the total renal neoplasms discovered over a 6-year period, and only one-third were initially identified by screening urography. While seven of the patients had hematuria, most had associated urologic conditions (calculi, prostatism). Two patients had widespread metastases 2 and 4 years after the carcinomas first appeared. The remaining seven patients are alive and well 8 months to 6 years after undergoing nephrectomy, despite the significant delayed diagnosis in three patients. Only one lesion was pathologically benign (an oncocytoma). Two of the renal cell carcinomas were found within the walls of partially calcified renal cysts. Two (22%) of nine neoplasms exhibited aggressive biologic behavior, which suggests that these lesions may have greater metastatic potential than previously thought. We suggest that computed tomography be performed after screening urography and cystoscopy when unexplained hematuria is present.