Acute Lymphocytic Leukemia (ALL)

Overview
  • Acute Lymphocytic Leukemia (ALL) is an aggressive neoplasia of the early lymphocytic precursor, termed the "lymphoblast". Like all acute leukemias, ALL follows a rapid course and clinical consequences are largely the result of marrow infiltration. In general, ALL is a disease of the children and can be rapidly fatal if not treated.
Pathogenesis
  • ALL is caused by neoplastic transformation of lymphoblasts, an early progenitor of lymphocytes in the normal sequence of hematopoiesis. Like all acute leukemias, neoplastic cells initially proliferate in the bone marrow and can then spill out into the peripheral blood as well as solid lymphoid organs such as the spleen, lymph nodes, and liver.
Morphology and Subtypes
  • ALL "blasts" share common features with those of all acute leukemias, visible as large cells with large nuclei that possess a fine granular cytoplasm and nucleoli. Unlike the blasts of AML, those of ALL do not possess cytoplasmic granules and instead display clumps of periodic acid-Schiff (PAS)-positive material.
  • Although indistinguishable histologically, immunophenotyping can categorize ALL cells into those with predominantly B-cell or T-cell markers. Most ALLs are those of B-cell lineage and these carry a slightly better prognosis than those of T-cell lineage.
Clinical Consequences
  • Like all acute leukemias the clinical consequences of ALL are largely the result of bone marrow infiltration, potentially leading to bone pain as well as a myelophthisic anemia with consequent pancytopenia. Infiltration of the spleen, liver, and lymph nodes can result in splenomegaly, hepatomegaly, and painless lymphadenopathy. In a minority of cases, seeding of the CNS can result in neurological impairments.