UTERINE SARCOMAS: HISTOGENESIS AND TAXONOMY

before proposing a system of classification, I should like to consider t he histogenetic aspects of uterine sarcomas. In most cases, histogenesis is st raight forward once i he neoplasm has been classified correctly. For example. leiomyosarcoma, the most frequently encountered form, is derived from adult smooth muscle. Tumors of blood-vessel origin are derived from pre-existing d u l t blood vesc;els, which are ubiquitous i n the uterus ss i n any other viscus. ’The few instances of lymphosarcoma or reticulum cell s;irconi;i that arise i n the uterus either de nmo or as part of multicentric tumorigenesis are derived from lymphoid or reticuloendothelial cells, which are likewise ubiquitous. The only group of uterine sarcomas that poses a histogenetic problem is the group of >o-called “mixed” or ”mixed mesmchymal” or “mixed mesodermal” tumors. This group is of particular import ance because. historically, there ha.: been much debate concerning its nature, particularly with respect to explanations for the diversity of cellular elements i t may contain atid with respect to the problem of tlie relationship of malformation to tumor. hIany of the theories held in the past have been discarded as either not probable or not provable. For example, J. F. (’ohnheim’s theory of displ;ic.ed rests is not given much credence today. 11 . m’ilms’ theory, which v . 7 ; ~ ~ it >lightly more sophisticated version of the rest. theory, implied an invisible rest, that is, ;I group of cells indistinguishable from uormally matured cells, but lacking the capacity for coordinated response to normal stimuli for growt t i and differentiation. Wilms explained the presence of cartilage and bone i t i mixed tumors on the basis of inclusion of structures from the sclerotome into tlie caudal por‘tion of tlie growing Wolffian duct. J. E. Sweet applied Wilms’ ideas to AIiillerian duct derivatives as well. T t is not clear from reading eithcr Wilms or Sweet whether they thought their theories were a further definition of Schwalbe’s concept of a “dysontogenetic field” or : is something opposed t o i t . Robert. nleyer advanced theories of displacement still further by postulating “illegal cell connections” between Wolffian and Mullerian systems as the origin of mixed tumors. Some reinforcement of lreyer’s theory can be fouiicl in the observation of Gruenwald,l who demonstrnted that the growing caudal end ol thc 3\liillerian duct is in contact with a n d surrounded by the same basement membrane as the growing end of the Wolffian duct. Possibly, Neyer’s illicit cell connections may not. prove to he as illegal as the embryologic. knowledge of his day permitted him to think. €Towever, oc.xxsionaliy tlie presence of a displaced rest is noted. In only one case have I cvcr seen mything in a tumor that rcmotely might be considered a rest. This w:ts i n :I case of sarcoma botryoidcs of the cervix of a 21-year-old woman reported by Edgcornb and myself.’ In the middle of this poorly differentiated neoplasm