Objectives. To review the pathologic findings of a contemporary series of surgically treated renal tumors suspicious for malignancy to assess the frequency of benign disease in the modern era. The extensive application of modern imaging techniques has led to an increase in the number of incidentally discovered solid renal masses, many of which are small. A significant proportion of small renal tumors are benign or are low-grade malignancies. Methods. The records of all patients at our institution who underwent treatment for a renal mass suspicious for malignancy between November 1999 and July 2002 were retrospectively reviewed. Results. A total of 173 patients with 186 renal tumors had pathologic information available for analysis. Of the 186 tumors, 48% were discovered incidentally. For masses 4 cm or less, the percentage of incidentally discovered tumors increased to 58%. The pathologic evaluation demonstrated malignancy in 160 (86%) and benignity in 26 (14%) overall. For tumors 4 cm or less, 18 (20%) of 90 were benign; for tumors between 4 and 7 cm, 8 (17%) of 47 benign. No tumors greater than 7 cm were benign. All renal cell carcinomas less than 2 cm in size were Fuhrman grade 1 or 2. Conclusions. Small renal tumors, many of which are incidentally discovered, are often benign or are low-grade malignancies. For tumors 4 cm or less, the frequency of benign pathologic findings is greater than previously quoted in published reports. As a result, we recommend parenchymal-sparing approaches whenever possible.
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