In addition, an immunohistochemical analysis of RCC revealed that preoperative serum GGT levels significantly correlated with tissue GGT levels which were semi-quantified by the intensity of immunohistochemical staining (i.e., negative to weak, moderate, and strong) at the respective median serum GGT levels of 29, 48, and 109 U/L (p = 0.004) [11]. Here, GGT1 is linked to renal cell carcinoma.