AllergoOncology: Emerging Translational and Clinical Significance of Basophils and Mast Cells in Cancer.

Mast cells and basophils, historically defined by their pathogenic roles in allergic diseases and type I hypersensitivity, are increasingly recognized as influential participants in cancer biology. Emerging research in AllergoOncology highlights their plasticity, diverse functions, and significance beyond classical contributions to allergy. This review summarizes current evidence on their presence, activation states, and roles across multiple cancer types. We examine their interactions with other immune populations, their context-dependent pro- and anti-tumor functions, and their potential utility as biomarkers. Their pro-tumor activities include secretion of Th2 cytokines, release of angiogenic mediators, and facilitation of extracellular matrix remodeling, all of which can support tumor progression. Conversely, these cells may also promote anti-tumor immunity through effector mechanisms and recruitment of cytotoxic CD8+ T cells. Translational tools such as the basophil activation test (BAT) and the mast cell activation test (MAT) are emerging to help predict hypersensitivities to cancer treatments including immunotherapies. A deeper understanding of their dynamic roles within the tumor microenvironment (TME) and across anatomical locations may reveal previously underappreciated functions, prognostic value, and therapeutic opportunities.