Quantitative cytochemistry of glucose-6-phosphate dehydrogenase in benign and malignant breast tumours.

Glucose-6-phosphate dehydrogenase (G6PD) activity was quantified cytochemically in mammary epithelial cells within frozen tissue sections from 38 patients with breast cancer and 44 with benign breast disease. G6PD activities were measured under atmospheres of both N2 and O2. The mean (S.E.) G6PD value 2.5 (0.23) IE U/min measured in N2 in mammary epithelial cells from the group of malignancies was significantly greater than that of 1.6 (0.37) IE U/min in the benign group (P less than 0.001), but there was considerable overlap between individual values. G6PD measured in O2 was detectable in 84% of malignancies compared to only 14% of benign biopsies and the group mean of 1.3 (0.18) IE U/min in the former was significantly greater than that of 0.35 (0.20) IE U/min in the latter (P less than 0.001). Significant correlations between G6PD activities measured in N2 and O2 were observed in both groups. The techniques present a sensitive method of identifying increases in G6PD activity in mammary epithelial cells and provide an assay that in a majority of cases permits the separation of malignant from benign tissues.