Lymphoid leukemias — also called lymphocytic, lymphogenous, or lymphoblastic leukemias — are a group of leukemias affecting circulating lymphocytes, a type of white blood cells. 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.