Classification of ALL In acute lymphoblastic leukemia, the precursor lymphoid neoplasms are broadly categorized based on their lineage into B-lymphoblastic leukemia / lymphoma (B-ALL / LBL) T-lymphoblastic leukemia / lymphoma (T-ALL / LBL) Disease can manifest as leukemia when neoplastic cells (lymphoblasts) involve blood and bone marrow (defined as > 20% bone marrow blasts) or as lymphoma when blasts infiltrate mainly extramedullary tissue.