The present invention provides a therapeutic agent and others for various tumors including angioimmunoblastic T-cell lymphoma (AITL), which is an orphan disease. The present invention relates to a therapeutic agent and others for tumors identified by phosphorylation of a proto-oncogene protein belonging to the VAV family, which comprises dasatinib or a prodrug thereof or a pharmacologically acceptable salt thereof or a hydrate or solvate thereof as an active ingredient.
