Here we show that surgical cavity seroma from breast cancer patients has a higher expression of certain tumor-promoting cytokines, including GRO, ENA-78/CXCL5 and TIMP-2, and lower expression of tumor-inhibiting cytokines IGFBP-1, IL-16, IFN-γ, IL-3 and FGF-9, when compared to seroma from non-cancer patients. Here, IFNG is linked to cancer.