Immunohistochemical detection of glucose transporter GLUT1 in benign and malignant fallopian tube epithelia, with comparison to ovarian carcinomas

Context. - Enhanced expression of GLUT1, a facilitative glucose transporter found on red blood cells, blood-brain barrier, and perineurium, has been described in a large spectrum of epithelial malignancies. Objective. - We present an immunohistochemical survey of GLUT1 expression in benign and malignant fallopian tube epithelia, and compare serous carcinomas of the fallopian tube and ovary. Design. - One hundred two routinely fixed and processed archival specimens (36 benign fallopian tubes, 29 primary tubal adenocarcinomas, and 37 primary ovarian adenocarcinomas) were immunostained with rabbit anti-GLUT1 and developed with streptavidin-biotin/diaminobenzidine. Only distinct membrane staining was scored positively (1+ to 3+). Results. - Benign tubes (n = 36) were either negatively stained (58.3%) or displayed rare weak staining (0.5+ to 1+, rarely 2+; 41.7%); of the latter, 4 specimens showed chronic salpingitis, and 6 showed hyperplasia (epithelial tufting and stratification). A case of florid hyperplasia with atypia in a BRCA1-positive patient was GLUT1 negative. Twenty-three (79.3%) of 29 tubal carcinomas were positively stained. Staining ranged from focal/scattered foci (n = 15) to myltifocal/extensive (n = 8). Of the 6 nonstaining tubal carcinomas, 3 were undifferentiated. Nineteen tubal carcinoma sections showed residual benign epithelium, which was consistently nonstaining. Very frequently, GLUT1 staining intensified in cells furthest from stroma/stromal capillaries and/or bordering necrotic zones. On average, GLUT1 staining in primary fallopian tube cancers was less extensive than in primary ovarian adenocarcinomas. Conclusions. - GLUT1 immunostaining of fallopian tube adenocarcinomas was substantially stronger and more extensive than staining of benign tubal epithelium, consistent with previously described findings in carcinomas versus benign tissues from many primary sites. The frequent localization of GLUT1 positivity to regions most distal from stroma/stromal capillaries is consistent with known activation of GLUT1 expression by hypoxia-sensing cellular pathways and may constitute a survival advantage under hypoxic conditions present in malignancy. The difference in extent of GLUT1 staining between primary tubal and primary ovarian serous adenocarcinomas is discussed.