CSF3R and chronic neutrophilic leukemia: In a report of 35 cases of clinically suspected CNL in whom JAK2V617F screening was performed, three individuals harbored JAK2V617F mutations but only one with truly WHO-defined CNL (but lacking the prototypical CSF3R mutation)76, supporting the apparent mutual exclusivity of JAK2 and CSF3R mutations, yet allowing for JAK2 positivity in exceptional cases of CNL.