Atypical chronic myeloid leukemia, BCR/ABL-neg, in relapse

This code describes a rare and aggressive form of myelodysplastic/myeloproliferative neoplasm characterized by features of both chronic myeloid leukemia and myelodysplastic syndromes, but without the Philadelphia chromosome (BCR/ABL fusion gene). It indicates that the disease, after a period of remission or improvement, has returned or worsened.

Assign this code when documentation confirms a diagnosis of atypical chronic myeloid leukemia that is explicitly stated as BCR/ABL-negative and is currently in a state of relapse. This typically follows a period of treatment where the disease was controlled.

• Ensure documentation clearly specifies "BCR/ABL-negative" to differentiate from classic CML.
• Confirm the "in relapse" status is explicitly documented by the clinician, indicating recurrence after a period of remission.
• Do not confuse with other myeloproliferative neoplasms or myelodysplastic syndromes; the specific "atypical CML" diagnosis is crucial.