BCOR and acute promyelocytic leukemia: Other kinds of atypical APL such as NuMA-RARα, NPM-RARα, F1P1L1-RARα, BCOR-RARα and PRKAR1A-RARα positive APL are proved to be effective to ATRA and ATO.[30,31] In a word, although atypical APL is rare, it remains a challenge to all of us.