The present invention provides a novel method for determining cancer malignancy, a novel cancer diagnostic method, a novel method for determining prognosis, a novel vaccine for cancer treatment, and a novel vaccine for suppressing cancer metastasis. Specifically, the invention provides a cancer malignancy evaluation method that comprises the step of measuring a DDX3X expression level in a cancer tissue, and the step of evaluating malignancy of the cancer tissue by using the DDX3X expression level.
