ANGIOMATOID MALIGNANT FIBROUS HISTIOCYTOMA REVISITED - AN IMMUNOHISTOCHEMICAL AND DNA-PLOIDY ANALYSIS

A histologic, immunohistochemical, and DNA ploidy analyses were perfor med on two cases of angiomatoid malignant fibrous histiocytoma to asce rtain the histogenesis and relationship of endothelial, histiocytic, a nd fibroblastic elements. Both cases were slowly growing, grossly enca psulated, subcutaneous masses resected from pediatric patients. Micros copically, the tumors were composed of solid masses of epithelioid and spindle cells with abnormal endothelial-lined and blood-filled cystic spaces surrounded by normal vascular structures and aggregates of lym phocytes occasionally forming germinal follicles. The tumor cells stai ned exclusively with CD34 and vimentin antibodies. Tumor-associated ve ssels stained for CD31, CD34, vimentin, and Ulex europaeus. Occasional cells within germinal follicles stained for lysozyme, CD68, and HAM56 . Ploidy analysis of tumor cells showed intermediate aneuploidy with a DNA index of 1.14. Blood vessels within and surrounding the tumor as well as inflammatory cells were DNA euploid. These studies suggest tha t the tumor-though comprised of histologically and immunohistochemical ly benign-appearing euploid endothelial, fibroblastic, and inflammator y elements-contains an aneuploid population of undifferentiated mesenc hymal cells.