Two cases of fibrous mesothelioma are presented. The first is a malignant tumor containing bundles of spindle-shaped cells with a dense reticulin network and nests of epithelial-like cells. The second is a benign tumor made up of spindle-shaped cells arranged in bundles with abundant reticulin and collagen fibers. Tissue culture in the first case revealed plagues similar to those formed by epithelial tumors. The second case had a fibroblastic pattern with single isolated spindle-shaped cells. These findings confirmed the mesothelial nature of fibrosarcomatous mesothelioma and supported the view that the so-called localized fibrous mesotheliomas could be fibroblastic neoplasms derived from the submesothelial connective tissue.

Forty-eight cerebral astrocytomas and glioblastomas were studied by tissue culture for two purposes: (a) the establishment of a definite growth pattern of cerebral astrocytomas and (b) the comparison of this growth pattern and that of glioblastomas. According to the grade of malignancy the series was divided into four groups: low-, middle-, and high-grade astrocytomas and undifferentiated glioblastomas. All the astrocytomas showed the same growth pattern with two successive phases. First, bipolar cells in radial arrangement emigrated from the explant, whereas in the last weeks, multipolar astrocytic-like cells in reticular arrangement predominated. The more malignant the cases, the more prolonged the bipolar phase, with retardation of the development of multipolar cells. Glioblastomas showed the same behavior with maximal persistence of the bipolar phase. On this basis, we believe that (a) cerebral astrocytomas have a characteristic behavior in vitro and (b) the glioblastoma is an astrocytic tumor showing maximal dedifferentiation.

Astrocytomas have been alternatively considered as a single entity with topographical variabilities or as two different tumours--cerebral astrocytomas and mid line-cerebellar, astrocytomas. Twenty-two astrocytomas, 13 of the cerebral hemispheres, six cerebellar, two brain stem and one of spinal cord, have been studied by short-term tissue cultures. Two distinctive growth patterns have been found. Cerebral astrocytomas grew in the first week as radially arranged bipolar cells and subsequently by multipolar astrocytes in a reticular pattern. On the other hand, astrocytomas of the cerebellum, brain stem and spinal cord showed radial growth of long bipolar cells which persisted during the first 2-3 weeks. Only in the fourth week did a reticular pattern develop, but most of the cells remained bipolar. After the fourth week, a small number of multipolar astrocytes appeared and in two cases Rosenthal fibres were found. It is thus suggested that astrocytomas may be subdivided into two entities, those of the cerebral hemispheres and others in the cerebellum, optic nerve, brain stem and spinal cord which can be grouped as midline astrocytomas.