We have previously shown that the breast cancer cell lines MDA-MB-231 and MCF-7 express the IL-10R and that exposure to cmvIL-10 results in enhanced cell proliferation and migration [57, 58]. In the present study, we examined the impact of cmvIL-10 on MDA-MB-231 cell invasion through a simulated basement membrane and investigated the effect of cmvIL-10 on a panel of metastasis-related genes. We found that cmvIL-10 was a potent enhancer of invasion and influenced expression of genes strongly linked to the metastatic spread of breast cancer.