Here we propose a hypothesis that a tumor prognosis prediction system based on ILCs can be constructed in the following aspects: (1) the levels and proportions of type 1 and type 2 cytokines; (2) the levels and proportions of anti-tumor cytokines (mainly IL-9) and pro-tumor cytokines (IL-4, IL-13 and amphiregulin); (3) the levels and proportions of ILC and ILC2 subsets in peripheral blood and lesions. The gene discussed is IL9; the disease is neoplasm.