<prompt> Most of the ALLs have -B - cell originT-cell originNK cell originNone  <response>: Acute lymphoblastic leukaemialymphoma Acute lymphoblastic leukaemia ALL encompasses a group of neoplasms composed of immature, precursor B Pre-B or T Pre-T lymphocytes referred to as lymphoblast.The majority 85 of all ALLs are precursor B-cell tumors that typically manifest as childhood Leukemia with extensive bone marrow and variable peripheral blood involvement.The less common precursor T-cell ALLs tend to present in adolescent males as lymphomas, often with thymic involvement.The peak incidence of Pre B-cell ALL is evident between 3-5 years and ALL is the most common childhood cancer.Pre T-cell ALL occurs in adolescent male.Morphology of tumor cell lymphoblast.Having scant cytoplasm and nuclei somewhat larger than those of small lymphocytes.The nuclear chromatin is delicate and finely stippled and nucleoli are either absent or inconspicuous.Contain cytoplasmic aggregates of Periodic acid Schiff PAS positive material. Clinical manifestationsSymptoms related to depression of normal marrow function.An accumulation of neoplastic blast cells in the bone marrow suppresses normal hematopoiesis by physical crowding and competition for growth factors.This results in : -Anemia Fatigue, pallorNeutropenia Infection, feverThrombocytopenia Bleeding, petechiae, ecchymoses, epistaxis.These are the most common sign symptoms.Bone pain tendernessResulting from marrow expansion and infiltration of the subperiosteal.Generalized lymphodenopathy, Splenomegaly and hepatomegaly.Caused by neoplastic infiltration of these tissues.More common in ALL than AML.Symptoms related to compression of large mediastinal vessels or airway.In Pre-T ALL of thymus.CNS manifestationDue to meningeal involvementA headache, vomiting, nerve palsies.More common in ALL than in AML.Testicular involvement is also more common in ALL than in AML.NoteThe FAB diagnostic criteria for acute leukaemia is the presence of 30 blasts in bone marrow normal 5.According to WHO classification, blasts should be 20 in bone marrow for diagnosis of acute leukaemia. 