# Case Report: Isolated acetabular myeloid sarcoma as the initial presentation of extramedullary blast crisis in chronic myeloid leukemia: a report of two cases and literature review

## TL;DR

This paper reports two rare cases of myeloid sarcoma as the first sign of chronic myeloid leukemia, highlighting diagnostic challenges and aggressive disease progression.

## Contribution

The novelty lies in describing two new cases and a literature review of a rare CML subtype with extramedullary blast crisis and MS as initial presentation.

## Key findings

- Two patients presented with hip pain and soft tissue masses, initially misdiagnosed as non-Hodgkin lymphoma.
- Molecular analysis confirmed CML in extramedullary blast phase with mutations in TP53, KMT2D, and STAG2.
- Despite treatment, both patients had aggressive disease progression and died within a year.

## Abstract

Myeloid sarcoma (MS) as the initial manifestation of chronic myeloid leukemia (CML), while the bone marrow (BM) remains in the chronic phase, is exceedingly rare.

We report two cases of MS initially presented with hip pain and soft tissue masses. Both patients had unremarkable complete blood counts and BM morphology, and initial core needle biopsies were misinterpreted as non-Hodgkin lymphoma. Further cytogenetic and molecular analyses, however, identified the Philadelphia chromosome, BCR::ABL rearrangement, and mutations in TP53, KMT2D and STAG2, establishing the diagnosis of MS secondary to CML in extramedullary blast phase. Both patients received tyrosine kinase inhibitors with or without chemotherapy, nevertheless, their disease progressed rapidly, resulting in death within one year.

Through a comprehensive literature review, we identified 33 additional reported cases with the same diagnosis. This disease predominantly affects middle-aged men, with bone and parosteal soft tissues being the most common involved extramedullary site. Such patients may constitute a biologically distinct subgroup and, in some reports, have shown relatively favorable outcomes. However, our cases follow an aggressive clinical course, possibly influenced by high-risk molecular features. Large-scale clinical studies are required to clarify the biological heterogeneity of this subgroup and to optimize therapeutic strategies.