KRT7 and kidney neoplasm: However, if doing a biopsy of the renal mass and the histology alone is not conclusive, immunohistochemistry is useful because TTF-1 which is a typical marker for adenocarcinoma in the lung is negative in primary renal neoplasms [9] and a CCR which represents 80% of the kidney cancer expressed often the CD10 and the vimentin with no expression of the CK7.