<prompt> Most common malignant tumour in childhoodRhabdomyosarcomaLeukemiaLymphangiomaNeuroblastoma  <response>: Leukemia is the most common malignancy of childhood.There are two main subtypes,the commoner acute lymohoblastic leukemiaALL acute myeloid leukemiaAML.A small propoion may have chronic myeloid leukemiaCML and juvenile myelomonocytic leukemiaJMML.ALL is the most common childhood malignancy accounting for one-fouh of all childhood cancers. Reference:Essential pediatrics-Ghai,8th edition,page no:599. 