Contribution to the study of 150 cases of cerebral metastases. II. Neuropathological study.

This study deals with the morphology of 150 cases of cerebral metastases. They are, for the most part, associated to other cases of metastases elsewhere in the body (96.7%). A histological study shows that the nervous parenchyma is more frequently invaded by expansion than infiltration; the majority of metastases settle in the grey matter or where the white matter meets the cortex. There is no predominance for one of the two hemispheres. The frequency of metastases in the various lobes is proportionate to their respective volumes. In 30% of the cases, there is only one single metastasis; these are then, very often, tumours from the digestive tract and from the breast. Usually they are large, and especially if they originate from the digestive tract. Single metastases are three times more frequent in the brain than in the cerebellum. In 10% of the cases, only the cerebellum is affected by metastases. Breast tumours are by far the most frequent kind of tumor to invade the dura. The widely accepted principle that the brain is invaded by means of the arteries is confirmed by our series, where no document shows an illustration in support of the venous theory. In most cases, the metastases are of the same histological type as the primary tumour. More or less deep necroses are found quite often. These disorders of vascular permeability explain fairly clearly the varying responses of the environing nervous tissue to the tumours invasion, particularly in the presence of hemorrhages. When they are voluminous, they may clinically have appeared in the form of an ictus. These hemorrhages occur preferably in the white matter. Necroses are sometimes cavitary, their centre being taken up by a necrosis of liquefaction, surrounded by a more or less continuous neoplastic border. The most frequent inflammatory reaction is lymphoplasmocytarian, particularly accentuated on the periphery of the metastasis and in the neighbouring meninges. Oedema predominates in the white matter. They nearly always lead to demyelinization, with its aftermath of granulofatty bodies or astrocytarian reactions. Fibrosis is also frequent, it is intra-metastatic and in direct relationship with the tumour's histological type; it is more rarely perimetastatic, developing from the vascular mesenchyma. The vascular changes constitute one of the most constant peri-metastatic parenchymatous alterations. They may appear in the form of vascular ectasia or neoformations of vessels, the most characteristic aspect of which is the formation of vascular glomerules. These undergo a very quick evolution and are indubitably linked to the degree of malignancy.