[Clinical factors associated with benign renal tumors]

In this study, we sought to define the incidence of benign renal tumors in our institute and to clarify the clinical factors associated with benign renal tumors, in order to assist in forming preoperative differential diagnoses.

From October 2002 to July 2007, we performed 157 nephrectomies in patients preoperatively diagnosed with renal cell carcinoma. We chose 81 tumors, all of which were less than 5 cm, for further study. We reviewed double-phase helical CT imaging retrospectively, specifically focusing on attenuation patterns and homogeneity. We also compared clinical factors, including age, sex and tumor size, between the benign and malignant renal tumors.

The patient's median age was 67 years (mean age, 63 years), and the median tumor diameter was 3.0 cm (mean, 3.2 cm). Benign renal tumors were found in 10 (12%) of the 81 tumors; these included seven cases of oncocytoma and three cases of angiomyolipoma with minimal fat. Several factors were significant clinical determinants of differentiation between benign and malignant renal tumors: homogeneity in CT, female gender, and small tumor size all predominated in cases of benign tumors. Attenuation pattern in CT, however, was not a significant factor (p = 0.344).

When a patient, especially a female, presents with a small and homogeneous renal tumor, careful consideration should be given to the possibility of a benign process, which needs further consideration before performing excessive surgery.