Leukemia

Definition

Leukemia or leukaemia (Greek leukos λευκός, "white"; aima αίμα, "blood") is a cancer of the blood or bone marrow and is characterized by an abnormal proliferation (production by multiplication) of blood cells, usually white blood cells (leukocytes). It is part of the broad group of diseases called hematological neoplasms.

Classification

Leukemia is a broad term covering a spectrum of diseases.

Leukemia is clinically and pathologically split into its acute and chronic forms.

• Acute leukemia is characterized by the rapid increase of immature blood cells. This crowding makes the bone marrow unable to produce healthy blood cells. Acute forms of leukemia can occur in children and young adults. (In fact, it is a more common cause of death for children in the US than any other type of malignant disease). Immediate treatment is required in acute leukemias due to the rapid progression and accumulation of the malignant cells, which then spill over into the bloodstream and spread to other organs of the body. Central nervous system (CNS) involvement is uncommon, although the disease can occasionally cause cranial nerve palsies.

• Chronic leukemia is distinguished by the excessive build up of relatively mature, but still abnormal, blood cells. Typically taking months to years to progress, the cells are produced at a much higher rate than normal cells, resulting in many abnormal white blood cells in the blood. Chronic leukemia mostly occurs in older people, but can theoretically occur in any age group. Whereas acute leukemia must be treated immediately, chronic forms are sometimes monitored for some time before treatment to ensure maximum effectiveness of therapy.

Combining these two classifications provides a total of four main categories:

Four major kinds of leukemia

Cell type Acute Chronic

Lymphocytic leukemia

(or "lymphoblastic") Acute lymphocytic leukemia (ALL) Chronic lymphocytic leukemia (CLL)

Myelogenous leukemia

(also "myeloid" or "nonlymphocytic") Acute myelogenous leukemia (AML). Chronic myelogenous leukemia (CML)

Within these main categories, there are typically several subcategories. Types outside these main categories include hairy cell leukemia.

Comparison of leukemia types

Type Occurrence 5-year survival rate Overall treatment

Acute lymphocytic leukemia Most common type of leukemia in young children. This disease also affects adults, especially those age 65 and older. 85% in children and 50% in adults[1] Bone marrow and systemic disease control, prevention of spreading, e.g. to CNS

Chronic lymphocytic leukemia Most often affects adults over the age of 55. It sometimes occurs in younger adults, but it almost never affects children. ⅔ of affected are men. 75%[2] Incurable

Acute myelogenous leukemia Occurs more commonly in adults than in children, and more commonly in men than women. 40% [3] Bone marrow and systemic disease control, specific treatment of CNS, if involved

Chronic myelogenous leukemia Occurs mainly in adults. A very small number of children also develop this disease. 90% [4][5]

Hairy cell leukemia About 80% of affected people are adult men. 96% to 100% Incurable, but easily treatable