Local cellular responses associated with dormancy and regression of a syngeneic C3H mammary carcinoma

Summary Histological examination of subcutaneous implants of a C3H mammary carcinoma regressing after a period of growth in syngeneic female recipients showed that regression was concomitant with a local cellular reaction that covered the tumor without incursion by effector cells into the tumor. Regressing tumors and tumors in arrested growth appeared to be avascular. There was no evident tendency for responding host cells to make contact with tumor cells, and where close contact between lymphocytes and tumor cells existed at the periphery of the tumor, there were no signs of direct toxic effect on the tumor cells. When tumor pieces that included significant numbers of plasma cells were implanted into normal mice, the local cellular reaction was unusually rapid and abundant. This type of reaction did not develop against similar tumor pieces implanted into presensitized mice.