Subplamalemmal linear densities (SLD) consist of a thin layer of electron dense material immediately subjacent to the inner leaflet of the palsma membrane. Short segments of extracellualr basal lamina-like material or collagen fibers usually overlie them. SLD has been considered to be a possible morphologic maker of cells of mesodermal origin. The present study confirms the fact that SLD may be of value in the diagnosis of mesodermal or mesenchymal tumor.