Leukemia is a blood cancer characterized by a rapid production of abnormal white blood cells called blasts. These malignant cells may be found in the bone marrow, where the blood cells are generated, and in the peripheral blood (i.e. in circulation within the blood vessels). As the disease progresses, the leukemic white blood cells swamp out the healthy blood cells, preventing them to perform their functions, like fighting infections or avoiding serious bleeding.

Like other cancers, there are many types and subtypes of leukemia. The most simple classification includes only four types of leukemia based on two parameters: evolution (chronic or acute), and cell lineage (myeloid or lymphoblastic/lymphocytic. Chronic leukemias typically have an indolent evolution, i.e. progress slowly over the years, whereas acute leukemias are more aggressive and may be fatal in few weeks.

For a correct diagnosis, physicians must take into account a lot of different information: the clinical features and the results from the morphology (shape, size and other characteristics of the malignant cells seen by microscopy), immunophenotyping (proteins expressed by the malignant cells seen by flow cytometry) and genetics analysis.

Types Of Leukemia

The different types of leukemias are associated with different symptoms, prognoses, treatments, and genetic causes. Part of making a correct diagnosis involves analyzing patients blood cells under a microscope after chemical staining, called a “blood smear”. Different leukemias are associated with different visual features of blood cells, such as their shape, color upon staining, and size.

There are several different types of leukemia:

Other types of blood and bone marrow malignancies include:

  • Myeloproliferative Neoplasms (MPN)
  • Myelodysplastic Syndromes (MDS)
  • Systemic Mastocytosis (SM)
  • Multiple Myeloma
  • Hodgkin Lymphoma
  • Non-Hodgkin Lymphoma

Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a blood cancer caused by uncontrolled proliferation of abnormal myeloid precursor cells. It accounts for approximately 90% of all acute leukemias in adults. The incidence of AML increases with age. Most patients with AML are aged 65 years and over. Only 6% of patients, more or less, are younger than 20 years. AML prognosis is very poor, with a 5-year survival of < 10% in patients older than 60 years at diagnosis. The prognosis is better in younger patients.

The immature precursor cells of the myeloid lineage are called myeloblasts, and they normally develop into neutrophils, monocytes, eosinophils, basophils, erythrocytes, and megakaryocytes.

With Acute Myeloid Leukemia, the myeloblasts do not develop into healthy cells, resulting in neutropenia, anemia, thrombocytopenia, and in the clinical manifestations of bone marrow failure, which include pallor, fatigue, fever, bruising, and bleeding.

Acute Myeloid Leukemia is diagnosed when there is a percentage greater than or equal to 20% myeloblasts, monoblasts, or promonocytes, erythroblasts, or megakaryoblasts in the peripheral blood or bone marrow, except in patients with the certain cytogenetic abnormalities and who are classifed as having AML irrespective of blast count.

Acute Myeloid Leukemia was the type of Leukemia that Peter was diagnosed with in 2018. The disease was completely missed in a standarad blood test just one month before he was diagnosed as terminal with AML, this lead to our first research project Peter Moss Acute Myeloid & Lymphoblastic Leukemia AI Research Project, and ultimately, the formation of Asociación de Investigacion en Inteligencia Artificial Para la Leucemia Peter Moss.

The American Cancer Society's estimates for leukemia in the United States for 2019 are:

  • About 21,450 new cases of acute myeloid leukemia (AML). Most will be in adults.
  • About 10,920 deaths from AML. Almost all will be in adults.

Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL), also known as acute lymphocytic leukemia, is a cancer that affects the lymphoid blood cell lineage. It is the most common leukemia in children, and it accounts for 10-20% of acute leukemias in adults. The prognosis for both adult and especially childhood ALL has improved substantially since the 1970s. The 5- year survival is approximately 95% in children. In adults, the 5-year survival varies between 25% and 75%, with more favorable results in younger than in older patients.

Lymphocytes include: 1) B cells, that produce antibodies to help fight infection; 2) T cells, that help B cells to fight infection; 3) Natural Killer (NK) cells that attack cancer cells and viruses.ALL is caused by lymphoid blasts, or lymphoblasts, and may be classified as B cell precursor ALL, mature B-cell ALL, or T ALL. NK cell leukemia is very rare.

B-cell ALL commonly presents with fever, fatigue, bone or joint pain, bleeding or anorexia (signs of bone marrow infiltration). T-cell ALL most commonly presents with anterior mediastinal mass, which may cause variable symptoms, from dry cough or shortness of breath to a medical emergency called superior vena cava syndrome (obstruction of blood flow through the superior vena cava). Generalized lymphadenopathy (enlarged lymph nodes) and hepatosplenomegaly (enlarged liver and spleen) are also frequent in T-cell ALL.

Acute Lymphoblastic Leukemia is diagnosed when abnormal lymphoblasts are present in bone marrow or in circulation. Although there is no consensus regarding a minimal proportion of lymphoblasts in bone marrow, the diagnosis of ALL should be avoided when there are < 20 percent of lymphoblasts. Under normal circumstances, blasts don't make up more than 5% of bone marrow cells.

The American Cancer Society’s estimates for acute lymphocytic leukemia (ALL) in the United States for 2019 (including both children and adults) are:

  • About 5,930 new cases of ALL (3,280 in males and 2,650 in females).
  • About 1,500 deaths from ALL (850 in males and 650 in females).

Document Contributors

Rita Rb-Silva

Rita Rb-Silva

Medical Advisor (Hematology)

Ho Leung Ng

Alumni: Ho Leung Ng

Leukemia Drug Discovery

Adam Milton-Barker

Adam Milton-Barker