[Ultrastructure of capillary permeability in human brain tumor--Part 6: Metastatic brain tumor with brain edema].

Metastatic brain tumors very often cause severe brain edema. We examined ultrastructural findings of capillaries of these tumors and discussed the causes of cerebral edema as compared with those of glioblastoma which were previously reported. Four specimens were examined: two adenocarcinomas from the lung, one squamous cell carcinoma from the lung and one adenocarcinoma from the breast. These replicas and ultrathin sections were examined by transmission electron microscope. The following characteristic structures were detected; the capillary endothelium was proliferated, had marked infolding, and an increased number of pinocytotic vesicles and vacuoles. Short and elongate intercellular junctions were present. No open junction was detected. The basal lamina lost its three layered appearance and was irregular in width. Among these, an appearance of capillary fenestration was the most conspicuous features and observed in almost all capillaries. Two different pathogenesis for making vasogenic edema are proposed in metastatic brain tumor and glioblastoma. The frequent fenestration of the former and activated pinocytotic vesicles of the latter are responsible for extravasation of the edema fluid. The differences in distribution patterns of fenestration in metastatic brain tumor cannot be identified with respect to histological types.