Lymphoid leukemia

Lymphoid leukemias are a group of leukemias affecting circulating lymphocytes, a type of white blood cell. The lymphocytic leukemias are closely related to lymphomas of the lymphocytes, to the point that some of them are unitary disease entities that can be called by either name (for example, adult T-cell leukemia/lymphoma). Such diseases are all lymphoproliferative disorders. Most lymphoid leukemias involve a particular subtype of lymphocytes, the B cells. Historically, they have been most commonly divided by the stage of maturation at which the clonal (neoplastic) lymphoid population stopped maturing: Acute lymphoblastic leukemia Chronic lymphocytic leukemia However, the influential WHO Classification (published in 2001) emphasized a greater emphasis on cell lineage. To this end, lymphoid leukemias can also be divided by the type of cells affected: B-cell leukemia T-cell leukemia NK-cell leukemia The most common type of lymphoid leukemia is B-cell chronic lymphocytic leukemia. B-cell leukemia describes several different types of lymphoid leukemia which affect B cells. Other types include (with ICD-O code): 9826/3 – Acute lymphoblastic leukemia, mature B-cell type 9833/3 – B-cell prolymphocytic leukemia 9940/3 – Hairy cell leukemia T-cell leukemia describes several different types of lymphoid leukemias which affect T cells. The most common T-cell leukemia is precursor T-cell lymphoblastic leukemia. It causes 15% of acute leukemias in childhood, and also 40% of lymphomas in childhood. It is most common in adolescent males. Its morphology is identical to that of precursor B-cell lymphoblastic leukemia. Cell markers include TdT, CD2, CD7. It often presents as a mediastinal mass because of involvement of the thymus. It is highly associated with NOTCH1 mutations. Other types include: Large granular lymphocytic leukemia Adult T-cell leukemia/lymphoma T-cell prolymphocytic leukemia In practice, it can be hard to distinguish T-cell leukemia from T-cell lymphoma, and they are often grouped together.