gamma-Glutamyl transpeptidase activity in benign and malignant human mammary epithelial lesions. Histochemical evaluation.

gamma-Glutamyl transpeptidase (GGT) has been identified in many tissues. The enzyme is present in normal human serum and is accepted widely as an indicator of liver disease. gamma-Glutamyl transpeptidase has been characterized as a putative hepatocellular carcinoma marker in rats and humans and a similar role is suggested in carcinomas of other tissues, including breast, colon, and ovary. Using a histochemical technique to demonstrate GGT activity, we have defined characteristic staining patterns for 67 normal or benign, and 108 overtly malignant human breast lesions. Transitions between benign, atypical, and malignant tumors were observed as were differences between intraductal and infiltrating components of a tumor. Normal breast epithelium and nondysplastic proliferative lesions were characterized by concentrated apical and luminal staining with weak cytoplasmic activity. Malignant lesions exhibited diffuse cytoplasmic staining when staining was observed.