The value of differential diagnosis of renal tumors with eosinophilic cytoplasm

A majority of renal neoplasms consists of those with epithelial origin and malignant neoplasms. Of the malignant renal tumours, % 85-90 are renal cell carcinomas (RCCs). On the other hand oncocytomas, form % 3.2-7 of primary renal tumours. RCCs have poor prognosis and there are significant differences between survival rates of their subtypes. In particular, differential diagnosis of renal tumours with granular-eosinophilic cytoplasm, is of critical importance.The study was conducted on 64 nephrectomy materials diagnosed as RCC and oncocytoma at the Pathology Department of Fırat University of Medicine, Department of Pathology School from 1988 to 2009. Of these tumours, 23 were classical RCC, 15 were papillary RCC, 13 were chromophobe RCC and 13 were oncocytoma. The cases were grouped according to histopathologic types, nuclear degrees, pathological stages, age groups and sexes. These tumours were immunohistochemically applied CK7, CD117, EpCAM, Vimentin, RCCm and GST-?. The staining prevalence of these markers among RCC subtypes and oncocytomas, and the diagnostic contribution of staining patterns were examined.A statistically significant relation was found between RCCm, GST-?, EpCAM, CD117, CK7 and tumour types (p<0.05), while there was no such correlation with vimentin (p>0.05). A significant relation was established between RCC and pT (p<0.05), but not with age, sex, nuclear degree and tumour diameters.Additionally, sensitivity and specificity values of these six immunohistochemical markers were compared for the four tumour subtypes. It was found that GST-? was 100% sensitive in chromophobe and papillary RCC, and vimentin was 100% sensitive in oncocytoma. Similarly, CK7 was established to be highly sensitive in all four tumour types (80-96%). EpCAM had 100% sensitivity in chromophobe RCC and 33,3% sensitivity in papillary RCC. It was seen that RCC marker was 93.3% sensitive in papillary RCC and 87% sensitive in oncocytoma. It was found that CD117 was highly sensitive in classical RCC and oncocytoma.In conclusion, it was seen that positive RCCm and negative CK7 and CD117 were important in RCC diagnosis; positive EpCAM, CK7 and CD117 and negative GST-?, RCCm and vimentin were important in the diagnosis of chromophobe RCC; positive CK7 and RCCm and negative CD117 and GST-? were diagnostic in papillary RCC and positive CD117 and negative CK7, GST-? and vimentin were diagnostic in oncocytoma. We believe that use of the stated immunohistochemical markers in addition to morphological findings in renal tumours that pose diagnostic problems shall considerably contribute to correct diagnosis.Key Words: RCC, oncocytoma, immunohistochemisty