Microvascular pathology in the skeletal muscle paraneoplastic phenomenon.

: An electron microscopic investigation was made in order to study capillary alterations in the muscle paraneoplastic phenomenon associated with different malignant tumours. Several abnormalities were found including basement membrane widening and lamination, endothelial hypertrophy, a varied degree of lumen occlusion, and proliferative changes in pericytes. A degenerative process leading to capillary necrosis was also observed. A mononuclear cell infiltrate formed by macrophages, lymphocytes and mast cells was seen. The capillary changes observed suggest the existence of an autoimmune vascular factor in the etiopathogenesis of muscle damage in this phenomenon.