Arginase-1, encoded by the ARG1 gene, is a cytosolic metalloenzyme expressed predominantly in hepatocytes which plays a key role in the urea cycle by catalyzing the hydrolysis of arginine to ornithine and urea. Argininemia is an inherited autosomal recessive disorder characterized by a buildup of arginine and ammonia in the blood. Anti-Arginase-1 is highly specific for hepatocytes, and is therefore a sensitive and specific marker of benign and malignant hepatic tumors.