The available information to date suggests that PTEN abnormalities appear to be associated with adverse outcome in T-ALL, but the data are limited; the cohorts in some studies are small, not all studies have examined both mutations and deletions, and most studies have not considered the impact of the mutant level, in particular whether those with complete (biallelic) PTEN loss differ from those with partial (monoallelic) loss. Here, PTEN is linked to acute lymphoblastic leukemia.