Leiomyomatosis peritonealis disseminata. An ultrastructural study.

Electron microscopic features of the eighth documented case of leiomyomatosis peritonealis disseminata identify the main proliferative cell type as a mature leiomyocyte with all its associated ultrastructural features. The histogenesis of this neoplasm is considered to be a multicentric metaplastic change determined by an abnormal tissue response to the elevated hormonal levels occurring in pregnancy or ovarian functioning tumors. It is suggested that the cell of origin is the multipotent subcelomic mesenchymal cell, which retains the capacity to differentiate into several tissues, among them smooth muscle. To illustrate this possibility, myofibroblasts, cells with hybrid characters of fibroblasts and leiomyocytes, were observed; these may represent a transitional stage between the mesenchymal cell and the smooth muscle proliferating cell.