T-cell acute lymphoblastic leukaemia: subtype prevalence, clinical outcome, and emerging targeted treatments.

T-cell Acute Lymphoblastic Leukaemia (T-ALL) is a high-risk hematological disease constituting ~20% of acute leukemias. To date, the only subtype recognized by the World Health Organization's International Consensus Classification is early T-cell precursor ALL. To improve clinical outcomes, several studies have investigated and defined T-ALL genomic subtypes within cohorts of varied ages and geographical locations. These studies have also utilized differing analysis methods including whole transcriptome, exome, or genome sequencing as well as immunophenotyping and cytogenetic testing. As a result, there are significant differences in reported subtypes as well as the frequency at which each occurs. The reported clinical outcomes for specific genomic alterations also depend on patient demographics and treatment protocols. This review synthesizes the data from four T-ALL genomic landscape studies establishing consensus and highlighting differences, details clinical outcomes for the most common genomic alterations observed in T-ALL patients, and proposes novel avenues for future investigation and treatment.