Leukemia and lymphoma are most common childhood cancers

By Drs. Sally Robinson and Keith Bly

Two similar and common types of childhood cancer that affect entire systems of the body are leukemia and lymphoma.

Leukemia is cancer that affects bone marrow, which is the spongy center of the bones where blood cells are made. It is the most common type of childhood cancer - 35 percent of all children diagnosed with cancer have leukemia. It is most common in children under age 10. Blood consists of three main types of cells: white blood cells (also called leukocytes), red blood cells (erythrocytes) and platelets. Leukocytes protect the body against disease; erythrocytes carry oxygen to the body; platelets help blood to clot.

Leukemia is cancer of the white blood cells. When a child has leukemia, abnormal white blood cells grow in large numbers in the bone marrow, where they become crowded and eventually flow into the blood stream. But, because these leukocytes are abnormal, they cannot fight infection and they crowd out healthy leukocytes, erythrocytes and platelets. The cure rate for leukemia is very good. Most children undergo treatment, which usually consists of chemotherapy, sometimes combined with radiation.

Symptoms of leukemia are lethargy; back, leg and joint pain; headache; trouble standing or walking; easy bruising or unusual bleeding; frequent nose bleeds; bleeding gums; red pinpoints on the skin (known as petechiae); fever that lasts several days; loss of appetite; swollen lymph nodes; tender or bloated stomach; swollen liver or spleen; night sweats and irritability.

In general, leukemias are divided into two types: acute (rapidly developing) and chronic (slowly developing). Ninety-eight percent of all leukemias are acute. Acute leukemias are divided into acute lymphocytic leukemia and acute myelogenous leukemia, depending on whether or not specific types of white blood cells called lymphocytes are affected. Acute lymphocytic leukemia is the most common type of acute leukemia and usually occurs in children between ages 2 and 8, but it can occur in any age group.

Lymphoma is a cancer that affects the lymphatic system, which keeps the body's fluid levels in balance and protects the body against infection. Lymphatic tissues that are affected by lymphoma include the lymph nodes, thymus, spleen, tonsils, adenoids and bone marrow, as well as a network of channels that carry fluids throughout the body. Many types of cancer may eventually spread to parts of the lymphatic system, but lymphomas originate in the lymphatic system.

Lymphomas are separated into two general categories: Hodgkin's disease and non-Hodgkin's lymphoma. Hodgkin's disease affects about three in 100,000 Americans, and is most common during early (between 15 and 40 years of age) and late (after age 55) adulthood. It is characterized by a painless enlargement of lymph nodes located in the neck, above the collarbone, under the arms, or in the groin, caused by specific types of malignant cells.

Non-Hodgkin's lymphoma may occur at any age, but it rarely occurs before age 3, and it is slightly more common than Hodgkin's disease in children under the age of 15. In NHL, lymphocytes grow abnormally, just as they may in acute lymphocytic leukemia, making it difficult to distinguish between lymphoma and leukemia. People with lymphoma usually have little or no bone marrow involvement, while those with leukemia have extensive bone marrow involvement. If the spleen or liver are involved in the lymphoma, they will be enlarged.

Lymphomas are usually treated with a combination of chemotherapy, radiation and bone marrow transplants. The cure rates vary depending on the type of lymphoma and how far the disease has progressed.

Symptoms of lymphoma include swollen lymph nodes, facial swelling, weakness or tiredness, night sweats, unexplained fever, unexplained weight loss, abdominal pain or swelling, generalized pain, breathing difficulties including occasional cough and difficulty in swallowing.

For more information about leukemia or lymphoma, please visit www.leukemia-lymphoma.org.

Dr. Sally Robinson is a pediatrician in the division of children's special services at the University of Texas Medical Branch at Galveston. She teaches medical students about caring for children with chronic medical conditions. Dr. Keith Bly is a hospitalist and assistant professor of pediatrics at UTMB.

The Your Health column is written by health and medical experts at the University of Texas Medical Branch at Galveston. The column focuses on topical health issues that we believe are of interest to your readers. It is e-mailed every Tuesday. If you have any questions about the column, or would like to suggest topics, please contact John Koloen, media relations specialist, at (409) 772-8790 or email jskoloen@utmb.edu.