# First Case of FLT3-Tyrosine Kinase Domain Mutant Acute Myeloid Leukemia With Unusual Onset as Isolated Bilateral Testicular Myeloid Sarcoma

## TL;DR

This paper reports a rare case of testicular myeloid sarcoma with an FLT3 mutation, emphasizing the need for accurate diagnosis and targeted treatment.

## Contribution

The paper presents a unique case of FLT3-TKD mutant AML manifesting as bilateral testicular myeloid sarcoma.

## Key findings

- The patient was initially misdiagnosed with orchitis but later confirmed to have TMS after reevaluation.
- FLT3 tyrosine kinase domain mutation was identified, necessitating tailored therapy with tyrosine kinase inhibitors.
- The case highlights the importance of comprehensive FLT3 testing for accurate treatment planning in TMS.

## Abstract

Testicular myeloid sarcoma (TMS) is a challenging pathology often posing diagnostic difficulties due to the poorly differentiated nature of tumor cells at the initial presentation. The delay in diagnosis significantly impacts patient life expectancy, emphasizing the need for prompt identification and treatment initiation. In certain cases, the presence of the Fms-like tyrosine kinase (FLT3) mutation adds complexity to the disease, requiring tailored therapeutic approaches. In this report, we present a unique case of bilateral TMS with FLT3 tyrosine kinase domain (TKD) mutation. The patient exhibited an aggressive clinical course, initially misdiagnosed with orchitis during the initial evaluation. Subsequent reevaluation of the testicular biopsy at a second center led to an accurate diagnosis, highlighting the importance of thorough examination in challenging cases. Given the emerging significance of FLT3 mutations in myeloid sarcomas, comprehensive testing for all FLT3 variants is crucial to determine the appropriate treatment modality. This case underscores the need for increased awareness among healthcare professionals regarding the diagnostic nuances and potential genetic variations associated with TMS. Furthermore, the inclusion of tyrosine kinase inhibitors, such as midostaurin or gilteritinib, especially in the presence of FLT3 mutations, may significantly impact treatment outcomes.

This report contributes to the growing body of literature on TMS and highlights the importance of considering FLT3 mutations in the diagnostic and therapeutic decision-making process for improved patient care.