Ultrastructural observations of the stroma of human colon carcinomas with special regard to myofibroblasts.

The stroma of 18 human colon carcinomas was studied with regard to the occurrence of myofibroblasts. In addition, we tried to determine if there was any relationship between myofibroblasts and other stromal responses to tumor growth, e.g. immunologic inflammatory reactions or activation of vascular structures. We found myofibroblasts in 13 carcinomas, although only sporadically in 6 of them. In 5 carcinomas these cells were absent. The number of myofibroblasts showed an inverse relation to the quantity of inflammatory cells (mainly lymphocytes, plasma cells and histiocytes). A variable amount of activated vascular structures could be seen in all cases. In 5 tumors many activated vessels showed a multilayered basement membrane. The electron microscopic findings led to the conclusions that myofibroblast proliferation and immunologic inflammation are not positively correlated with each other and that vascular activation does not parallel myofibroblast induction. The significance of the individual components for tumor prognosis is briefly discussed and the need for further work to clarify the role and mode of interaction of the different factors in tumor-induced stromal response is emphasized.