GLUT1 glucose transporter: a highly sensitive marker of malignancy in body cavity effusions.

Malignant cells exhibit increased rates of glycolysis and glucose uptake, and several types of cancer have been reported to overexpress the GLUT1 glucose transporter. The diagnosis of malignancy in body cavity effusions remains a dilemma in certain cases, despite recent progress in diagnostic immunocytochemistry. We used immunostaining to detect the facilitative glucose transporter, GLUT1, in cytologic preparations of body cavity effusions and washes. With the use of standard avidin-biotin immunostaining for GLUT1, we examined cell blocks of body cavity effusions or washings from 31 carcinomas, 1 lymphoma, and 25 benign effusions or washes. GLUT1 staining occurred in the malignant cell population in 29 (93.5%) of 31 carcinomatous effusions or washes. The characteristic staining pattern consisted of dense, linear staining of the plasma membrane, with accentuation at cell-cell borders, with or without cytoplasmic staining. Erythrocytes showed positive GLUT1 membrane staining, consistent with previous reports. Of 25 benign effusions, 20 were nonstaining (excepting erythrocytes), and 5 contained rare single mesothelial cells, with equivocal to very weak membrane staining. Staining of these cells was readily distinguishable from the characteristic strong staining of malignant cells, and these cells were easily distinguished from tumor cells by their benign morphologic characteristics. At least three of these latter five specimens were from patients with cirrhosis. In all of the other cases, mesothelial cells, histiocytes, and other inflammatory cells did not stain. These findings suggest that GLUT1 immunostaining could be useful in diagnostic cytopathology. The findings also suggest that enhanced glycolysis, which requires increased glucose transport, might be a survival adaptation for tumor cells in effusions, a significant number of which are hypoxic.