The myofibroblastic nature of the uterine plexiform tumor.

Electron microscopic study of rare, benign, plexiform tumor of the uterus showed that of its component cells exhibit characteristics of both smooth muscle cells and fibroblasts, which allows for their identification as myofibroblasts. Although such cells have been more frequently associated with reactive processes, their presence in some malignant soft tissue tumors, viz, fibrosarcoma and malignant fibrous histiocytoma, has been noted by others. Analysis of recorded accounts, as well as our own limited personal experience with the ultrastructural characteristics of smooth muscle neoplasms and those putatively regarded as being of such origin, indicates that many of these may contain a relatively large complement of myofibroblasts. The spectrum of myofibroblastic differentiation of smooth muscle cells and/or fibroblasts may account for the varied interpretations that concern the derivation of some of these neoplasms, particularly hemangiopericytoma.