CUTANEOUS ADULT MYOFIBROMA - A VASCULAR NEOPLASM

Infantile myofibromatosis is a distinctive type of fibromatosis that u sually develops during the immediate perinatal period. There are varia nts with solitary and multiple tumors. Lesions confined to the skin, s oft tissue, and bone carry a good prognosis, showing spontaneous regre ssion. The prognosis, however, is much less favorable when visceral le sions are present and the outcome may be fatal. Only recently it becam e obvious that there is an adult counterpart of infantile myofibromato sis, characterized by solitary lesions that have a predilection for in volve the dermis and show no tendency to regression, although they hav e an entirely benign biological behavior. These lesions have been name d cutaneous myofibroma or solitary myofibroma of adults. We have studi ed the clinical, histopathological and immunohistochemical characteris tics of 53 examples of cutaneous adult myofibroma. In addition, 2 case s were examined ultrastructurally. The patients were mostly adults wit h ages ranging from 6-83 years. The lesions presented as solitary, usu ally painless nodules of variable duration on the skin, usually locate d on the extremities. Histopathologically, four patterns were identifi ed: nodular or cellular type, multinodular or biphasic type, leiomyoma -like or fascicular type, and vascular type. A correlation between the histopathologic pattern and the lesional age was observed: vascular t ype of cutaneous adult myofibroma in early lesions, nodular and multin odular lesions in fully developed lesions, and leiomyoma-like or fasci cular type in late lesions; Immunohistochemically, the spindle cells w ere desmin negative, but expressed immunoreactivity for vimentin, pan- smooth muscle actin, and alpha-smooth muscle actin. Ultrastructurally, neoplastic cells showed characteristics of undifferentiated mesenchym al cells with features of fibroblasts, myofibroblasts and pericytes. P rimitive vascular formations were seen in the form of irregular clefts between adjoining cells. We conclude that cutaneous adult myofibroma is a little-known benign vascular neoplasm probably derived from myope ricytes. (C) Munksgaard 1996.