B lymphoblastic leukaemia or lymphoma with t(9:22) (q34;q11.2); BCR-ABL1

**Definition:** A precursor lymphoid neoplasm which is composed of B-lymphoblasts and carries a translocation between the BCR gene on chromosome 22 and the ABL1 gene on chromosome 9. It results in the production of the p190 kd or p210 kd fusion protein. It has an unfavorable clinical outcome.