A
rare neoplasm originating from pericytes which are cells in walls of
capillaries and venules external to endothelial cells and enveloped by a
basement membrane.The tumor
is usually small and singular, with more frequent symptoms than a
capillary hemangioma and more vascularity (#22120).This lesion frequently may recur after incomplete excision and may
potentially undergo a malignant transformation which may metastasize to
lungs, bone, liver, and regional nodes.Histopathologically, this lesion consists of numerous capillary
channels in a sinusoidal or staghorn pattern surrounded by solid areas of
spindle-shaped or round cells with uniform cellular morphology (#22123)
(#22122).A reticulin stain
is often helpful to outline the basement membrane.
