Cystic renal cell carcinoma.

Cystic renal cell carcinoma includes any malignant neoplasm of renal tubular epithelium which presents as a fluid-filled mass. Approximately 15 per cent of cases of renal cell carcinoma will be cystic on radiologic and pathologic examination. The clinical features of cystic renal cell carcinoma are similar to those which are solid. The radiographic and pathologic findings of cystic renal cell carcinoma are often more confusing and less specific than the findings of renal cell carcinoma which are predominantly solid. There are four basic pathologic mechanisms resulting in cystic renal cell carcinoma: intrinsic multiloculated growth; intrinsic unilocular growth (cystadenocarcinoma); cystic necrosis; and origin from the epithelial lining of a preexisting simple cyst. There are three basic radiologic patterns of cystic renal cell carcinoma: unilocular cystic mass, multiloculated cystic mass, and discrete mural nodule in a cystic mass. Cystic renal cell carcinoma is often extremely difficult to differentiate from non-neoplastic, benign neoplastic, and other malignant neoplastic masses utilizing radiologic studies alone. This review presents the clinical, pathologic, and radiographic features of cystic renal cell carcinoma and discusses its radiologic differential diagnosis.