Minor breakpoint cluster region (m‐BCR) positive chronic myeloid leukaemia with an acute lymphoblastic leukaemia onset: a case report

m-BCR chronic myeloid leukaemia (CML) is a rare entity. We report a patient presenting with Philadelphia (Ph)-positive, m-BCR-positive acute lymphoblastic leukaemia (ALL) who achieved complete remission after induction chemotherapy, but showed a majority of Ph-positive mitoses during this remission. A diagnosis of m-BCR CML was established and the patient was given interferon alpha therapy. This is the first m-BCR CML presenting as ab initio ALL. This report emphasizes the importance of karyotyping Ph-positive ALL during remission so as not to misdiagnose CML patients who can benefit from Interferon therapy.