A comparative ultrastructural study of leiomyosarcoma, cellular leiomyoma, and leiomyoma of the uterus

Abstract

An electron microscopic study was made of a uterine leiomyosarcoma, and this lesion was compared with normal myometrium and with uterine leiomyomas, one of which was of the cellular type. The leiomyomas had abundant myofilaments, well‐developed pinocytic activity, a well‐defined basement membrane, and an abundant extracellular collagenous matrix. The cellular leiomyoma bore a close ultrastructural resemblance to the smooth muscle cells of the ordinary leiomyomas and to normal myometrium. There was, however, increased nuclear size, and an increase in the number of mitochondria and cytoplasmic free ribosomes. The leiomyosarcoma was characterized by nuclear pleomorphism, scanty myofilaments, abundant mitochondria, and free ribosomes. Single cilia with centriolar apparati were occasionally encountered in both the cellular and ordinary leiomyomas but were absent in the leiomyosarcoma. This study suggests that the leiomyoma and leiomyosarcoma are distinct entities and that the cellular leiomyoma represents a variety of the common leiomyoma rather than an intermediate form between leiomyosarcoma and leiomyoma. Copyright © 1971 American Cancer Society