CD2 and acute lymphoblastic leukemia: Early T cell precursor (ETP) ALL is a subtype characterized by a unique immunophenotype (cCD3+, sCD3−, CD1a−, CD2+, CD5dim (<75%+) and CD7+) and positivity for stem cell and/or myeloid markers that represents 15% of T-ALL cases and was previously associated with a poor outcome [79,80,81].