Combined Immunohistochemistry for the “Three 7” Markers (CK7, CD117, and Claudin-7) Is Useful in the Diagnosis of Chromophobe Renal Cell Carcinoma and for the Exclusion of Mimics: Diagnostic Experience from a Single Institution

Figure 1

Representative expression of the “three 7” markers in 3 variants of CHRCCs. CHRCC is typically arranged in a solid figuration with delicate, incomplete fibrovascular septa containing two types of polygonal cells (chromophobe and eosinophilic cells) in a variable proportion (a); the tumor cells are diffusely and strongly positive for CK7 (b), CD117 (c), and Claudin-7 (d). The eosinophilic variant is characterized by the predominant sheets of eosinophilic cells mimicking RO (e) and is also readily highlighted by CK7 (f), CD117 (g), and Claudin-7 (h). This HOCT displays RO-like cells intimately admixed with CHRCC-like cells (i); in contrast to the negative staining in the RO-like cells, the CHRCC-like cells are typically immunoreactive for CK7 (j), CD117 (k), and Claudin-7 (l).