Persistent monosomy 7 in Philadelphia chromosome-negative cells without disease progression over nearly two decades of follow-up in chronic myeloid leukemia.

Monosomy 7 (-7) is frequently associated with myelodysplastic neoplasm/syndrome (MDS) and acute myeloid leukemia (AML). In chronic myeloid leukemia (CML), the acquisition of -7 in Philadelphia chromosome-positive (Ph-positive) cells is considered a high-risk feature for progression to blast crisis. However, the clinical significance of -7 in Ph-negative cells remains less unclear. We report a patient with CML who developed a - 7 clone in Ph-negative cells during tyrosine kinase inhibitor (TKI) therapy. The -7 clone emerged after 14 months of TKI treatment, persisted for nearly six years, and subsequently disappeared. The patient continued treatment with sequential TKIs under long-term surveillance. Over nearly 20 years of follow-up, there was no evidence of significant dysplasia or progression to AML. This case suggests that the occurrence of -7 in Ph-negative cells does not reflect TKI-induced genotoxicity and does not necessarily confer an increased risk of MDS or AML.