Claudin 7 (5D10F3)

Claudin-7 is a transmembrane protein involved in the formation of tight junctions between epithelial cells.1 Tight junctions restrict lateral diffusion of lipids and membrane proteins which physically define the border between the apical and basolateral compartments of epithelial cells. The Claudin family of proteins has been implicated in the pathogenesis of various human neoplasms. The differential diagnosis of chromophobe renal cell carcinoma (RCC) and oncocytoma is difficult by light microscopy, and yet important as chromophobe RCC is malignant, whereas oncocytoma is benign2. Membranous claudin-7 expression was detected in 67-100% chromophobe RCCs, compared with 0-7% clear cell RCCs, 28-90% papillary RCCs, and 26-45% oncocytomas.1,3 Distal nephron (distal convoluted tubule and thick ascending limb of Henle’s loop) epithelium showed strong membranous staining in 100% (174/174) of the cases.4