Primary leiomyosarcoma of the vagina. Light and electron microscopic observations

Three primary leiomyosarcomas of the vagina in adult women were studied by light and electron microscopy; two of the tumors were well differentiated and one was anaplastic. They were composed of fusiform cells containing elongated, blunt‐ended nuclei arranged in irregular bundles which stained red with the Masson's trichrome stain. The ultrastructure of the tumor cells revealed large, irregular nuclei with a tortuous and bizarre contour, particularly in the less‐differentiated tumor. The cytoplasm contained numerous thin myofibrils arranged in clusters and irregular bundles. Clumps of mitochondria were conspicuous at the nuclear poles; they exhibited irregular, dilated cristae which seemed to delineate a matrix of increased density. The granular endoplasmic reticulum had dilated cysternae containing finely granular electron‐dense material. The cells were loose with poor cohesiveness. However, marginal dense patches in adjacent cytoplasmic extensions were seen in the anaplastic tumor. The periphery of the cells had abundant pinocytotic vesicles in the differentiated tumor; they were very rare in the undifferentiated one. In both, the cells were coated by a basement lamina which appeared fragmented and poorly defined in some areas. In general, the ultrastructure of the cells is comparable to that of smooth muscle tumors in other organs. The ultrastructural identification of the tumor cells is highly valuable for the differential or confirmatory diagnosis of soft tissue tumors of the female genital system.