Expression of gamma-glutamyl transpeptidase in normal and neoplastic epithelial cells of human skin: a marker for distinguishing malignant epithelial tumours.

The distribution of gamma-glutamyl transpeptidase (GGT) activity was studied histochemically in benign and malignant epithelial tumours of human skin. We found that GGT activity in normal skin was confined to the secretory portion of the eccrine and apocrine glands and to the inner root sheath of the hair follicles. In Bowen's disease and actinic keratosis, GGT activity was noted focally in areas where atypical cells were observed. In extramammary Paget's disease, GGT activity was found only in large round cells scattered among GGT negative epidermal cells. No GGT activity was observed in basal cell epitheliomas or benign epithelial tumours, while squamous cell carcinoma and eccrine porocarcinoma exhibited intense GGT activity. Our study suggests that GGT may be useful as a histochemical marker for distinguishing malignant tumours from benign epithelial tumours in human skin.