Very Late Extramedullary Relapse of Acute Myeloid Leukemia 13 Years After Allogeneic Transplant: A Case Report.

The 2007 sample contained nine somatic variants, while the 2021 myelosarcoma harbored four variants.

Only a single somatic mutation, a frameshift alteration in the HNRNPK gene, located on 9q21, was shared across both timepoints, suggesting a potential founder event and supporting the hypothesis of clonal evolution.

Chimerism analysis and histopathological findings confirmed that the relapse originated from the patient rather than from donor-derived hematopoiesis.

The persistent HNRNPK mutation across both disease phases may point to a rare but critical driver of leukemogenesis and relapse.