Oncocytoma : CK7
Oncocytomas usually express EMA, pancytokeratin, low molecular weight keratins, CD117, S100 protein and E-cadherin. Vimentin is negative or focally positive. CK7 is usually negative or shows only scattered positive cells which represent entrapped epithelial cells of distal convoluted tubules. This image shows no CK7 expression in the tumor (lower right). Strong positivity in renal tubular epithelium on the upper left serves as a nice internal positive control.CD10 and RCC marker are negative.