Reorganization of molecular morphology of epitheliocytes and connective-tissue cells in morphogenesis and carcinogenesis.

Complete and incomplete transitions of epitheliocytes into cells of mesenchymal type, so-called epithelial-mesenchymal transitions (EMT), take place in many types of normal morphogenesis and in epithelial carcinogenesis. Connective tissue cells (fibroblasts) also undergo considerable morphological changes during normal morphogenesis and carcinogenesis, but their dynamics are less known. It is suggested that EMT and fibroblast dynamics may have some common step that is some united precursor cell type. The program for normal EMT can be activated in the course of multistep progression of epithelial carcinogenesis; this activation can be supported by cell selection as it provides a basis for dissemination of neoplastic cells from original tumor.