Glucose transporters are integral membrane glycoproteins involved in transporting glucose into most cells. There are many types of glucose transport carrier proteins, designated as Glut-1 to Glut-12. Glucose transporter type I (GLUT1), also known as SCL2A1, is a major glucose transporter in the mammalian blood-brain barrier. It is expressed in high density on the membranes of human erythrocytes and the brain capillaries that comprise the blood-brain barrier. GLUT1 is expressed at variable levels in many human tissues. GLUT1 overexpression is associated with tumor progression or poor prognoses of bladder, breast, cervical, colon, and lung carcinomas, as well as mesothelioma. Glut-1 is a sensitive and specific marker for the differentiation of malignant mesothelioma (positive) from reactive mesothelium (negative). Anti-GLUT1 is useful for distinguishing malignant mesothelioma (GLUT1(+)) from reactive mesothelium (GLUT1(-)).