An incidental papillary renal cell carcinoma in a unilocular renal cyst: A case report

Cystic renal cell carcinoma (RCC) is a malignant epithelial tumor arising in a pre-existing renal cyst. The renal cyst maybe multilocular or unilocular with the latter being an even rarer occurrence. Cystic renal malignancy arising in a unilocular cyst is quite rare with only a few cases reported till date, most of which are clear cell RCCs. Literature available with regard to staging tumor nodule in a benign unilocular cyst is limited. We report a case of a 52-year-old male presenting with a single large unilocular cyst which had a small solid nodule of papillary RCC in its posterior wall which was detected on microsopy. On pathologic examination, all cases of clinically/ radiologically benign renal cysts should be examined with a high index of suspicion as a small tumor focus may be present in the form of a nodule or in the free wall of the cyst which was initially missed.