A clinicopathologic and immunohistochemical review was made of seven cases of angiomyofibroblastoma. The patients were middle-aged women who had a slowly growing mass, measuring 1.5-6 cm in maximum dimension, located subcutaneously in the vulva. The tumors were well-demarcated and characterized by well-vascularized, alternating hypercellular and hypocellular edematous areas composed of bland, plump spindle- or oval-shaped stromal cells frequently aggregated around small blood vessels. An epithelioid appearance of the stromal cells was seen in two cases. Immunohistochemically, the stromal cells were consistently positive for vimentin and desmin, but negative for muscle specific actin, alpha-smooth muscle actin, myosin, cytokeratins, S-100 protein or von Willebrand factor. Ultrastructurally, the plump stromal cells had a small amount of peripherally located rough endoplasmic reticulum, numerous pinocytotic vesicles and abundant intermediate filaments, on which immunogold probes for desmin were localized, whereas fine filaments were few and there were no electron dense plaques. Thus, while the proliferating stromal cells expressed an immunohistochemical profile of peculiar myoid differentiation, ultrastructural findings differed from those of smooth muscle cells or those seen in typical myofibroblasts. At 1-4 years after surgery, there was no evidence of recurrence.