This document discusses acute lymphoblastic leukemia (ALL). It defines ALL as a malignant disorder of hematopoietic stem cells characterized by an increased number of white blood cells in the bone marrow or peripheral blood. ALL is classified based on the type of cell affected (lymphoblastic or myeloid) and whether the disease is acute or chronic. The document describes the epidemiology, risk factors, clinical presentation, investigations including blood tests and bone marrow biopsy, classification systems, treatment involving induction, consolidation and maintenance phases, supportive care, medications used, and prognosis for ALL patients.