T-Lymphoblastic Leukemia/lymphoma

T-lymphoblastic leukemia/lymphoma (WHO 2008),^:219 previously labeled precursor T-lymphoblastic leukemia/lymphoma (WHO 2001)^:219 is a form of lymphoid leukemia and lymphoma in which too many T-cell lymphoblasts (immature white blood cells) are found in the blood, bone marrow, and tissues, particularly mediastinal lymph nodes.^:635 Labeling as leukemia or lymphoma depends on which feature is more pronounced in a given situation, but has no biological or treatment implication.^:635

It is uncommon in adults, but represents 15% of childhood acute lymphoblastic leukemia and 90% of lymphoblastic lymphoma.^:635

The 2008 terminology dropped "precursor" to avoid linguistic redundancy because the lymphoblast is an immature precursor cell by definition.^:219