In addition, gain-of-function mutations in KIT, that is mutations that cause constitutive activation of the tyrosine kinase (TK), have been implicated in a variety of neoplasms including, gastrointestinal stromal tumours (GIST), mastocytosis, acute leukaemias, melanomas and other cancers [4], [5]. The gene discussed is KIT; the disease is mastocytosis.