TIM-3 as an immune and leukemia stem-cell biomarker in acute myeloid leukemia: diagnostic laboratory and translational perspectives.

Despite improvements in ELN-based risk stratification, acute myeloid leukemia (AML) still faces three significant challenges: relapse, resistance to therapy, and measurable residual disease (MRD). T-cell immunoglobulin and mucin-domain-containing molecule 3 (TIM-3/HAVCR2) is a clinically relevant AML biomarker, as it is enriched in CD34+CD38- AML leukemia stem cells, with limited expression in normal hematopoietic stem cells, and is involved in immune-checkpoint disruption in the leukemic microenvironment. This review focuses on the diagnostic, prognostic, and translational value of TIM-3 in AML, particularly in relation to clinical chemistry and laboratory medicine. We integrated existing knowledge from various cellular, molecular, and soluble analytical platforms, such as multiparameter flow cytometry, to identify leukemia stem cells based on TIM-3 expression, transcript and protein profiling analysis of HAVCR2, or soluble immunoassay of TIM-3/Galectin-9. The potential applications of TIM-3 in relapse-risk stratification, MRD refinement, immune profiling, and companion biomarker development are further explored. Several important laboratory parameters that influence clinical applicability are also discussed in this review, such as specimen-matrix selection, antibody clone variation, gating strategies and cut-off variability pre-analytical procedures, and cross-platform validation. More harmonized assay workflows, standardized reporting of results, prospectively validated thresholds, and demonstration of the clinical value of TIM-3 beyond known MRD and genetic risk models are needed to enable the translation of TIM-3 into routine AML laboratory practices. Therefore, TIM-3 should currently be regarded as a promising adjunctive AML biomarker; however, it is not recommended for standalone routine clinical decision-making outside clinical trials.