Central scar dilemma: Oncocytoma versus RCC

Case courtesy: SDIC, Bangalore

Central stellate non-enhancing scar, has been linked characteristically to oncocytoma. But unfortunately,

1. It is seen only in 1/3rd of oncocytoma cases, and renal cell carcinoma can also show those scars quite often. 
2. This patient was 55 yr old, which is a perfect age group for oncocytoma, yet renal cell carcinoma too have incidences in this age group only. 
3. Lesion appears well-encapsulated, and exophytic, which favour oncocytoma, yet medially capsule doesn't appear quite regular, and lesion appears infiltrative. 
4. Renal vein thrombosis may be seen in both RCC and oncocytoma, although not seen in this case.

In nutshell, radiology can give some good input, yet differentiating both is difficult. 5% of resected renal tumours turn-out to be oncocytoma. Yet, I favour diagnosing these kind of masses as renal cell carcinoma, as treatment of these masses should be surgical resection. Considering stage I renal cell carcinoma, renal sparing surgery may be thought in both the cases. Post-operative histopathology may bring some relief to patient if any, and improve prognosis if proven oncocytoma. Pre-operative prognosis is indeterminate.