Multilocular cystic renal cell carcinoma: clinicopathological features and preoperative prediction using multiphase computed tomography.

Objective: • To analyse the clinicopathological and radiological features of multilocular cystic renal cell carcinoma (MCRCC) and to determine the preoperative factors differentiating MCRCC from other cystic RCC (CRCC).

Patients And Methods: • The medical records of 53 patients with complex cystic renal masses evaluated by multiphase computed tomography (CT), surgically removed and confirmed as sporadic RCC were reviewed. • Of these 53 patients, 23 were classified as having MCRCC and 30 as other CRCCs, defined as RCCs with extensive cystic change or cystic necrosis. • Another 22 patients were treated for complex cystic renal masses presumed to be RCC and diagnosed as having benign cyst.

Results: • Benign cysts and MCRCCs were significantly more likely to be of Bosniak classification III than other CRCCs (77% vs 61% vs 27%, P= 0.001). • The mean Hounsfield unit (HU) during the corticomedullary phase (CMP) was significantly higher in other CRCCs, with HU ≥38 having 83% sensitivity and 80% specificity for predicting other CRCCs. • In a multiple regression model, Bosniak classification and mean HU during CMP were independent factors predictive of other CRCCs. • In the 41 patients with masses >4 cm in diameter, the combination of Bosniak classification IV and HU ≥38 during CMP showed 63% sensitivity, 96% specificity, 91% positive predictive value and 80% negative predictive value, yielding 2% false-positive and 15% false-negative rates.

Conclusions: • The mean HU during CMP and Bosniak classification can differentiate MCRCC from other CRCCs. • This could help in selecting an appropriate surgical method, such as nephron-sparing surgery, for complex cystic renal masses >4 cm.