[The preoperative diagnosis of complex renal cystic masses]

To analyze the preoperative diagnostic methodology in a series of patients with complicated cystic renal masses in relation to the definitive anatomopathological findings.

20 cases of asymptomatic complicated cystic renal masses in 19 patients submitted to surgical exploration are described. All cases were evaluated by US and CT. Fine needle punction-aspiration biopsy (FNPA) was done in 17 of the 20 masses and pre and postoperative anatomopathological analyses were performed.

Following the Bosniak classification for complicated cystic masses, the US study showed two cases were type I, 5 type II, 10 type III, and 3 type IV, while the CT findings showed no type I, 8 type II, 9 type III and 3 type IV. The definitive anatomopathologic diagnosis was that of renal cell carcinoma in 11 cases. All but one (type II) of these 11 cases were Bosniak III or IV. Nine had a preoperative FNPA which showed malignant cells in two cases, while the remaining 7 were negative. The preoperative biopsy was negative in one of the 11 cases with renal cell carcinoma. The remaining 9 cases of complicated renal mass were simple cysts complicated by hemorrhage or infection.

In our series, the use of the Bosniak classification system preoperatively highly correlated with the presumed benign or malignant nature of the lesion. FNPA biopsy, however, was not found to be very useful in the preoperative diagnosis of complicated cystic renal masses; it showed a sensitivity of 22% and a negative predictive value of 46.7%. Although the foregoing data have no statistical significance, a negative FNPA biopsy of a complicated cystic renal mass that raises reasonable doubts does not change the indication for a surgical exploration.