<prompt> Drug of choice for treatment of gastrointestinal stromal tumors is:RituximabImatinib mesylateAnagrelideDenileukin diftitox  <response>: Ans: B Imatinib mesylate Ref: Goodman Gillman, The pharmacological basis of therapeutics, 12th edition, Pg No. 1732-1734.Explanation:Imatinib mesylate is used in the treatment of Approved indicationsChronic phase of CIVILGIST- Gastrointestinal Stromal tumorChronic Myelomonocytic leukemiaHypereosinophilic syndromeDermatofibrosarconia protruberanceProgressive plexiform neurofibromatosisIt is also tried in Experimental and Not approved for routine useSystemic MastocytosisPulmonary hypertensionAlzheimer s diseaseLowering or reversing opioid toleranceDesmoid tumor 