Tumor complexity predicts malignant disease for small renal masses

Purpose: Approximately 20% to 30% of suspicious small renal tumors are benign. A significant proportion of malignant tumors are low grade and potentially indolent. We evaluated whether preoperative patient and tumor characteristics are associated with adverse pathological features. Materials and Methods: A total of 886 patients underwent robot-assisted partial nephrectomy, as done by 1 of 5 high volume surgeons. Demographic and clinical data were compared between patients with benign/malignant disease, clear cell/nonclear cell renal cell carcinoma and high/low grade tumors. Tumor complexity was quantified by R.E.N.A.L. (radius, exophytic/endophytic, nearness of tumor to collecting system or sinus, anterior/posterior, hilar and location relative to polar lines) nephrometry score and described as low - 4 to 6, intermediate - 7 to 9 or high - 10 or greater. Logistic regression analyses were performed to test the association between tumor and patient characteristics, and high grade renal cell carcinoma. Subanalyses were done for patients with renal tumors 4 cm or less. Results: High grade renal cell carcinoma was larger and more likely to develop in men. Patients with malignant tumors and with clear cell histology were more likely to have intermediate or high complexity tumors. Increasing tumor complexity independently predicted malignancy, high grade malignancy and clear cell histology on multivariate regression analysis (each p <0.05). Male gender was independently associated with malignancy and high grade renal cell carcinoma. When considering tumors 4 cm or less, tumor complexity predicted malignancy but not tumor grade. Conclusions: High R.E.N.A.L nephrometry score and male gender are associated with an increased risk of malignancy and high grade malignancy in tumors treated with partial nephrectomy.