IL10 and breast angiosarcoma: Moreover, IL-10 upregulates hyaluronic acid (HA) synthases (HAS) 1, 2, and 3 and stimulates fetal fibroblasts to produce an HA-rich matrix.147,148 Multiple studies have found an association between BA and increased serum levels and differential expression of IL-10.149, , -152 In BA, increased IL-10 levels at the time of Kasai surgery may be the residua of fetal wound healing from the time of initial damage, although it appears that the restorative effect of IL-10 is not able to outweigh the subsequent fibrosing and inflammatory response in these patients.