# Myeloid sarcoma masquerading as central nervous system diffuse large b-cell lymphoma: a case report and literature review

## TL;DR

A patient with a history of leukemia developed a brain tumor initially mistaken for lymphoma, but further testing revealed it was a myeloid sarcoma.

## Contribution

This case highlights the diagnostic challenges of myeloid sarcoma masquerading as lymphoma in the central nervous system.

## Key findings

- The tumor was initially misdiagnosed as diffuse large B-cell lymphoma due to B-cell marker expression.
- Comprehensive testing confirmed it was a myeloid sarcoma, an extramedullary relapse of the patient's AML.
- The case emphasizes the importance of considering myeloid sarcoma in AML patients with atypical presentations.

## Abstract

This report presents a challenging case of a 52-year-old male with a history of acute myeloid leukemia (AML) with t(8;21)(q22;q22.1)/RUNX1::RUNX1T1 who developed an intracranial mass during hematologic remission. Initial histopathological examination of the resected lesion, due to aberrant expression of B-cell markers (PAX-5, CD79a, c-Myc, Bcl-2), led to a misdiagnosis of diffuse large B-cell lymphoma (DLBCL). Subsequent comprehensive integration of clinical history, repeated bone marrow assessment, cytogenetics, fluorescence in situ hybridization (FISH), and extended immunohistochemistry(IHC) revealed the tumor to be a myeloid sarcoma (MS), representing an extramedullary relapse of his underlying AML. This case underscores the diagnostic pitfalls of MS, particularly within the central nervous system (CNS), and highlights the critical importance of considering MS in patients with a history of AML, especially those with genetic profiles predisposing to extramedullary disease, even when pathology initially suggests lymphoma.