Precursor lymphoid neoplasms

**Definition:** Neoplasms of immature malignant lymphocytes (lymphoblasts) committed to the B-cell or T-cell lineage. Neoplasms involving the bone marrow and the peripheral blood are called precursor lymphoblastic leukaemias or acute lymphoblastic leukaemias. Neoplasms involving primarily lymph nodes or extranodal sites are called lymphoblastic lymphomas.