Researchers say that people with diabetes have a 19 percent greater risk of getting non-Hodgkin’s lymphoma than those who don’t have diabetes. The increase in such lymphoma cases has paralleled the upward trend of diabetes. Why people with diabetes are at greater risk for non-Hodgkin’s lymphoma is unclear. The lymphoma occurs when circulating immune cells proliferate out of control. The researchers suggest the link may have to do with how diabetes affects the immune system. Obesity may also be a factor. 
Source: Diabetes Care, December 2008