MC‐1 can exert anti‐tumourigenic effect through cytotoxic action (ROS, TNF‐α and granzymes), production of IL‐9 that inhibit tumour cell engraftment, release of histamine promotes dendritic cell (DC) maturation and inhibits tumour growth; tryptase can be taken up into the nucleus of human melanoma cells causing truncation of histones and inhibition of cell proliferation. This evidence concerns the gene IL9 and neoplasm.