Types of Leukemia

Leukemia is not one disease. Although it is a form of cancer affecting blood cells, there are several types of leukemia and they can be either acute or chronic.

Almost 62,000 new cases of leukemia are diagnosed each year in the U.S., according to the American Cancer Society. But leukemia isn’t one single disease entity. Instead, leukemia describes several cancers of the blood cells.

Types of leukemia depend on the specific kind of blood cells that become malignant and whether the cancer is an acute form and progressing quickly or growing slowly and chronic.

Leukemia, including the acute and chronic types, can occur in people of any age, although the cancers develop in adults 10 times more often than in children, according to the Leukemia Research Foundation.

Although there are many types of leukemia, the most common forms are chronic and acute lymphocytic leukemia, and chronic and acute myelogenous leukemia.

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Understanding chronic lymphocytic leukemia

Chronic lymphocytic leukemia (frequently called CLL) is one of the most frequently diagnosed forms of leukemia in adults. It’s more likely to occur during or after middle age; children rarely are diagnosed with CLL.

There is some genetic component to this cancer. If there is a family history of CLL or cancer of the lymphatic system — or if your family ancestry includes Eastern European or Russian Jews — you may be at higher risk for this type of leukemia, according to the National Cancer Institute (NCI).

In CLL, excess number of white blood cells called lymphocytes develop but are abnormal and unable to fight infections in the body well. In addition, as the number of lymphocytes in the bone marrow and blood accumulate, they replace healthy red blood cells, white blood cells, and platelets. The result can be anemia, bleeding easily and being more prone to infections.

Chronic lymphocytic leukemia progresses slowly and may not cause any obvious symptoms, especially when it first develops. The disease is usually discovered during a check-up or other doctor visit.

When symptoms occur, they often include:

• Swollen lymph nodes in the neck, underarm, groin, or stomach
• Feeling unusually tired
• Pain or fullness below the ribs
• Unexplained weight loss
• Fever and infections

Tests to diagnose and stage the disease involve examining the blood, bone marrow, and lymph nodes. Because it is a chronic and usually slowly progressing disease, very early stage CLL may be managed by watchful waiting to see if and when the disease progresses.

Depending on the stage and symptoms, different types of treatments are used, including radiation therapy, chemotherapy, surgery (to remove the spleen, possibly slowing disease progression), and targeted therapy using drugs or other substances to identify and attack specific malignant cells without damaging normal cells, the NCI explains.

Why acute lymphocytic leukemia needs immediate treatment

The acute form of lymphoblastic leukemia (ALL) needs treatment as soon as possible because the disease can progress quickly. In fact, the American Cancer Society explains this type of leukemia, if untreated, can be fatal within a few months.

Like CLL, this leukemia starts in the bone marrow and develops from early forms of lymphocytes. But in ALL, the abnormal leukemia cells invade the blood quickly and can spread to the lymph nodes, spleen, liver, testicles in males, and the brain and spinal cord.

ALL is more likely to occur in children and people who are 70 and beyond. Exposure to high levels of radiation (such as exposure to an atomic bomb blast or nuclear accident) can cause ALL, but this kind of exposure is extremely rare.

However, treating cancer with medical doses of radiation does increase the risk of this leukemia somewhat, especially if chemotherapy is also used. Exposure to some toxic chemicals, including benzene (found in cigarette smoke and some cleaning products, art supplies, paint strippers, and glues) and certain chemotherapy drugs, is also a risk factor.

Although ALL doesn’t run in families, having specific genetic disorders such as Down syndrome may raise the risk of the disease.

Early symptoms of ALL can be similar to the flu or other common infections, the NCI points out. Other common signs include easy bleeding and bruising, night sweats, frequent infections, weight loss, and shortness of breath. There are several sub-types of ALL, depending on what areas of the body the leukemia is affecting, that can cause numerous other symptoms, including swelling in the abdomen, headaches, seizures, and bone pain.

Blood work, a physical exam, bone marrow biopsy, and other tests are used to assess ALL, but there are no standard stages for the disease, the NCI points out. Instead, once adult ALL has been diagnosed, tests can determine if the cancer has spread to the central nervous system (brain and spinal cord) or other parts of the body to decide on treatment. The main treatment for ALL in adults is typically long-term chemotherapy. Radiation therapy, chemotherapy with stem cell transplant, and targeted therapy may also occur.

Understanding chronic and acute myelogenous leukemia (CML)

Acute myelogenous leukemia (also called acute myelocytic leukemia) is another indolent (slow growing) type of leukemia. Like CLL, acute myelogenous leukemia (CML) typically appears in middle-aged or older adults and, rarely, in youngsters.

Your bone marrow produces a subtype of immature white blood cells, called myeloblasts, that normally grow, divide, and mature into infection-fighting white blood cells. But in CML, the bone marrow makes abnormal myeloblasts that don’t change into healthy, mature cells. Instead, the bone marrow keeps pumping out large amounts of abnormal white blood cells that don’t fight infections, causing a variety of problems.

Most people with CML have a gene mutation, the Philadelphia chromosome, which is believed to result in this type of leukemia. (However, it is not passed from parent to child).

Symptoms of CML can include fever, night sweats, fatigue, unexplained weight loss, and a pain of feeling of fullness below the ribs on the left side — due to a swollen spleen. However, the disease may not cause any readily apparent symptoms.

Routine blood tests for other reasons, like a routine physical, can sometimes find CML . Test results might show that a person's white blood cell count is very high, even though he or she doesn't have any symptoms. The same tests used for other forms of leukemia are conducted to find if the cancer has spread.

CML is classified by chronic phase (slowly progressing), accelerated phase (10 percent or more blood cells are immature myoblast cells), or the blastic phase (in medical terms, "blast" refers to immature cells, and the blastic phase in CML means 20 percent or more of blood cells are now immature myeloblasts). When symptoms such as extreme fatigue, fever, and enlarged spleen occur during the blastic phase, it is called a blast crisis.

Depending on the phase and individual patient’s condition, treatment may include targeted therapy, chemotherapy, biologic therapy, high dose chemo with stem cell transplant, donor lymphocyte infusion, and surgery.

If you are diagnosed with CML and have the Philadelphia chromosome, you may be treated with tyrosine kinase inhibitors (TKIs). TKIs block a protein produced by the chromosome, and the treatment may result in remission of the leukemia.

Acute myelogenous leukemia (AML) has the same signs and symptoms of CML — except the AML can develop very quickly, and people often know something is wrong and seek medical attention. Men are more likely to develop AML than women, and smoking is a known risk factor for this type of leukemia, according to the American Cancer Society.

Bottom line? It’s important to recognize and treat leukemia early

The NCI points out the survival rates for leukemia patients have improved dramatically over the past three decades, as new treatments have been developed. Although outcomes depend on the type of cancer, the patient’s age, and other factors, early diagnosis and treatment are important for the best prognosis.

If you, or anyone in your family has unexplained symptoms, make an appointment for a check-up. While possible signs of leukemia usually have other, less serious causes, don’t take chances: talk to your doctor.

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