ALK and mesenchymal cell neoplasm: The clinical success of tyrosine kinase inhibitors is proven by a number of examples, such as imatinib in BCR–ABL1 fusion-positive leukaemia patients [7], or the more recent crizotinib and ceritinib in patients with lung carcinomas and mesenchymal tumors harboring anaplastic lymphoma kinase (ALK) fusions [8, 9].