ALK and leiomyosarcoma: At molecular level, approximately 50% of IMT cases contain rearrangements involving the anaplastic lymphoma kinase (ALK) gene, leading to constitutive activation of the tyrosine kinase, as well as positive immunohistochemical staining for ALK [8], which distinguishes IMT from gastrointestinal stromal tumor (GIST), leiomyoma, and leiomyosarcoma.