Lymphomas are cancers that develop in the lymphatic system, which is part of the immune system. This disease is the third most common form of cancer among children, following leukemias and brain tumors. About 2,200 people under the age of 20 are diagnosed with lymphoma each year in the United States, according to the National Cancer Institute.
The lymphatic system includes a network of glands and vessels that transports lymph, a clear fluid that contains infection-fighting white blood cells, including lymphocytes. Lymphocytes develop from young cells called stem cells.
Lymphocytes circulate throughout the body and are concentrated in areas of the lymph system, such as the bone marrow, spleen, tonsils, thymus, and lymph nodes — small bean-shaped organs found in the neck, chest, abdomen, groin, and underarms.
Lymphomas develop when lymphocytes begin to grow and multiply uncontrollably. These abnormal cells can cause lymph nodes to enlarge and can spread to any other area of the body, including the bone marrow and the central nervous system.
There are two main types of lymphoma: Hodgkin lymphoma and non-Hodgkin lymphoma. Each of these types also has several different subtypes, related to how the lymph node tissue appears under the microscope, the types of cells affected, and other factors.
Hodgkin lymphoma, also known as Hodgkin’s disease, most commonly affects children aged 15 and older. Children with this disease typically have abnormal cells called Reed-Sternberg cells in the cancerous lymph node. These cells may develop from a type of lymphocytes known as B cells.
The more common subtypes of Hodgkin lymphoma in children and young adults include:
- Nodular sclerosis (NS) - Lymph nodes contain scar tissue (sclerosis), normal and abnormal lymphocytes, and Reed-Sternberg cells. This subtype affects 70 percent of children who have Hodgkin lymphoma.
- Mixed cellularity (MC) - Lymph nodes contain inflammatory immune cells and Reed-Sternberg cells. This form is most commonly diagnosed in children younger than 10.
- Lymphocyte predominance (LP) - Abnormal lymphocytes and Reed-Sternberg cells are concentrated in the cancerous lymph node. This form is also more common in younger children.
Doctors have not yet determined the cause of Hodgkin lymphoma. However, the Epstein-Barr virus (EBV), involved in mononucleosis, appears to play a role in Hodgkin lymphoma development in nearly half of children with the disease.
Non-Hodgkin lymphoma is more common in boys than girls. The majority of non-Hodgkin lymphomas are highly aggressive and fast growing.
The two main subtypes of tumors that affect children are:
- Highly aggressive (high-grade) tumors - Burkitt lymphoma, non-Burkitt lymphoma, and lymphoblastic lymphoma
- Intermediate-grade tumors - Follicular large-cell lymphoma, diffuse small cleaved cell lymphoma, mantle cell lymphoma, peripheral T cell lymphoma, immunoblastic diffuse large cell lymphoma, and anaplastic Ki-1 large-cell lymphoma (CD30+). These types of tumors are more common in adults, though they are sometimes seen in children.
Based on the way that the tumors behave, the subtypes of non-Hodgkin lymphoma that develop in children differ from those that develop in adults.
The most common symptom of lymphoma is one or more enlarged lymph nodes in the neck, underarm, or groin, which are usually painless. Enlarged lymph nodes in children with lymphoma may resemble the swollen glands of children who have a throat infection involving the lymph nodes.
Other frequent symptoms of lymphoma can include:
- Unexplained fever
- Night sweats
- Loss of appetite or weight loss
- Coughing or difficulty breathing
- Abdominal swelling (lymphomas in the chest or abdomen can grow to a very large size before symptoms appear)
If your child has a lymph node that becomes enlarged without explanation or remains enlarged for a prolonged period of time, you should consult a pediatrician. The doctor may prescribe a course of antibiotics to treat a possible infection before performing a more extensive evaluation.
If the lymph node remains enlarged or continues to grow after antibiotic treatment, the doctor may need to remove lymph node cells or tissue to examine it for signs of a more serious condition, such as lymphoma. This can be accomplished by removing cells through a fine-needle aspiration procedure under local anesthesia, which may lead to a lymphoma diagnosis. If a diagnosis is not obtained using this method, a surgeon can perform a more extensive biopsy procedure to remove lymph node tissue while your child is placed briefly under general anesthesia.