Mechanisms of contrast enhancement in human brain tumors

In order to elucidate the mechanism of contrast enhancement on computed tomography observed in glial, non-glial, and metastatic tumors, tumors vessels were studied with conventional ultrathin-section and freeze-fracture replica techniques. Contrast enhancement on CT scan defined the order of non-glial, metastatic, and glial tumors. The materials were obtained from surgically removed specimens in 16 cases of glial (5 astrocytoma, 5 glioblastoma, 2 ependymoma, and 4 medulloblastoma), 19 cases of non-glial (6 meningioma, 6 hemangioblastoma, 5 pituitary adenoma and 2 acoustic neurinoma), and 4 cases of metastatic tumors (1 adenocarcinoma from the breast, 2 adenocarcinomas from the lung, and 1 squamous-cell carcinoma from the lung). The results indicate that the vesicular transport of a contrast material through increased pinocytotic vesicles has an important role in the contrast enhancement of glial tumors, while the extravasation of contrast material through fenestrations serves to effect a marked contrast enhancement of non-glial and metastatic tumors. The osmotic opening of tight junctions by a contrast material and the irregular basal lamina and large perivascular space may also contribute to an increased extravasation of the contrast material in the two groups. The fundamental characteristic of tumor vessels in glial tumors was to be non-fenestrated, whereas non-glial and metastatic tumors were fenestrated. (author)