Histological differential diagnostics of renal oncocytoma

The morbidity rate of kidney cancer has been increasing. Management of patients and their prognosis depend on the specific histological type of tumor. Unfortunately, different renal tumors can have similar histological features, making differential diagnostics challenging. Among the most challenging tasks is differential diagnosis of renal oncocytoma (RO) and chromophobe renal cell carcinoma (ChRCC).

To analyze different histological features of renal oncocytomas and specify their pathognomonic characteristics that may be advantageous for the confirmation of the diagnosis.

The medical records and histopathological reports of 197 patients with diagnosis of either RO or ChRCC were analyzed. 37 histological parameters were then evaluated and their prevalence in RO or ChRCC was compared by performing a contingency table analysis. Odds ratio was also calculated.

The most common growth patterns of ROs were solid (53%), nested (47%), cystic (29%), and alveolar (28%). A combination of two or more growth patterns was seen in 82% of cases mostly composing of nested, cystic, alveolar or solid structures. Most tumors exhibited granular inclusions (70%) and dense cytoplasm (58%).

With more than 95% confidence, the nested pattern, myxoid stroma, granular cytoplasm and round nuclei are likely indicative of RO, whereas the varying nuclear size, raisinoid nuclei and reticular cytoplasm indicate higher likelihood of ChRCC. Therefore, these features should be analyzed for RO confirmation.