Acute lymphoblastic leukemia (ALL) is a cancer of the lymphoid line of blood cells characterized by the development of large numbers of immature lymphocytes.[1] Symptoms may include feeling tired, pale skin color, fever, easy bleeding or bruising, enlarged lymph nodes, or bone pain.[1] As an acute leukemia, ALL progresses rapidly and is typically fatal within weeks or months if left untreated.[11]

Reference
Wiki: Acute B-cell lymphoblastic leukemia