Unmasking myeloid sarcoma: A SEER database study of an underrecognized malignancy

Abstract Introduction: The classification of “myeloid sarcoma” (MS) is often considered imprecise and misleading. A more accurate term is extramedullary acute myeloid leukemia (eAML), as it represents an extramedullary proliferation of immature granulocytic cells. Little is known about this entity and its outcomes due to its rarity. eAML can present with or without synchronous or metachronous intramedullary acute myeloid leukemia (AML) so a bone marrow evaluation is always recommended. It can affect any site, requiring biopsy, immunophenotyping, and molecular testing for diagnosis and treatment planning. Early systemic chemotherapy is recommended, even in nonleukemic cases. Surgery or radiotherapy may be used for localized or symptomatic lesions causing dysfunction or obstruction. Our study investigates the survival trends of myeloid sarcoma in different age, gender, ethnicity and treatment groups using Survival, Epidemiology, and End Results (SEER) database. Objective and Methodology A population-based analysis of MS was performed using SEER Research Plus data (17 registries, Database ID: 2536) from 2000 to 2022.A total of 604 patients were identified using ICD 9930/3 code. Patients were classified by race, gender, therapy received, and age (<65 vs 65+). Kaplan-Meier curves were used to visualize differences in survival. Data was noted for significance based on standard and weighted (Gehan-Breslow-Wilcoxon) Log-Rank tests. Results: Of the 604 patients, elderly patients (age 65+, 57.45%) had the poorest outcomes, with a median survival of 3 months, compared to 8 months in patients under 65 (42.55%) (P-value <0.0001). Gender was not a significant factor in survival. In terms of race, Caucasian patients (71.2%), had a worse median survival at 4 months, compared to an average of 7 months in patients of other races (28.8%) (P-Value 0.0006). Treatment analysis revealed that there was no significant difference in overall survival between patients who received treatment (62.25%) with a median survival of 7 months. Patients who received no treatment (37.75%) had a median survival of just 1 month (P < 0.0001). The impact of combination therapies could not be definitively assessed due to small sample sizes, but in some cases, combined treatments were associated with poorer survival than monotherapy approaches. Conclusion Discrepancies in survival were observed between different age groups, likely due to comorbidities and differences in candidacy for treatment, with treatment showing a clear survival benefit, though no treatment has a clear advantage over any other. Caucasian patients have worse survival, but we lack statistical power to assess additional differences between other ethnicities. Further studies are needed to better understand the etiology and mechanisms of this rare entity, as well as to explore therapeutic strategies beyond conventional chemotherapy—ideally in the context of controlled clinical trials. Keywords: Myeloid Sarcoma, Chloroma, Granulocytic Sarcoma, Extramedullary AML.