The lymphatic system is composed of a network of lymphatic vessels, lymph nodes, spleen, thymus, and lymphoid nodules present in the mucous membranes of the digestive, respiratory, and urinary tracts, as well as in the tonsils and adenoids. It is responsible for protecting the body from infectious agents and foreign substances, as it circulates defense cells such as lymphocytes, macrophages, and dendritic cells.
Lymphomas are neoplasms that originate in the cells of the lymphatic system as a result of genetic alterations that influence the proliferation of lymphocytes and their precursors, leading to malignant transformation and uncontrolled growth.
It is the third most common neoplasm among the most common cancers in childhood, surpassed only by acute leukemias and tumors of the Central Nervous System. There are different types of lymphomas, some of which grow very slowly and others very rapidly.
Patients with lymphoma have a high probability of cure with current therapeutic regimens, provided that the diagnosis is early and the disease is low-grade.
Types of lymphoma
Lymphomas are divided into two types: Hodgkin’s lymphoma (HL) and non-Hodgkin’s lymphoma (NHL). Both have different cellularity, behaviors, signs, and degrees of aggressiveness. The severity in both types will depend on the staging (degree of disease dissemination) at the time of diagnosis.
- Hodgkin Lymphoma: Among childhood neoplasms, 6% are Hodgkin lymphomas and are rarely observed in children under 5 years of age. It can arise in any part of the body where lymphoid tissue is widely distributed. Lymph nodes (swellings) grow rapidly, most commonly in the neck, supraclavicular, axilla, and chest region. Patients with Hodgkin lymphoma have a high probability of cure as long as the treatment is individualized for each child according to the tumor subtype, disease staging (degree of dissemination), and tumor mass size.
- Non-Hodgkin Lymphoma: represents 7% of neoplasms in childhood. It has a lower incidence in children than in adults, with the peak incidence in childhood occurring from 5 to 15 years and being more frequent in males.
Around 60% of lymphoma cases in children and adolescents are
Non-Hodgkin lymphomas, and the cure rates range from 60% to 90%, depending on the clinical characteristics of each patient. They are classified according to the lineage of origin into B-cell lymphoma or T-cell lymphoma and in a rare form of anaplastic large cell lymphoma called NK lymphoma. The most common Non-Hodgkin lymphomas in the pediatric age group are Burkitt lymphoma, lymphoblastic lymphoma, and large cell lymphoma. Non-Hodgkin lymphomas in children are generally of three types:
- Lymphoblastic lymphoma – accounts for about 25% to 30% of lymphomas in children and adolescents, with a incidence in boys twice as high as in girls. Most cases develop from T cells and can grow rapidly;
- Burkitt lymphoma – represents about 40% of lymphomas in children and is more common in boys between 5 and 10 years old. It almost always starts in the abdomen and, because it grows quickly, it is very important to start treatment as soon as possible; and
- Large cell lymphoma – can grow anywhere in the body and is more common in teenagers. It has two subtypes: anaplastic large cell lymphoma (usually starts in the skin, lungs, bones, digestive system, or other organs) and diffuse large B-cell lymphoma (begins as a rapidly growing mass in areas such as the thoracic-mediastinal region, abdomen, neck, and bones).
Symptoms and signs of lymphoma
Childhood NHL is mostly fast-growing, aggressive, and highly disseminating. The symptoms are the same for Hodgkin and non-Hodgkin lymphoma. The main signs of the disease are:
- Swollen lymph nodes in the neck, groin, and armpits;
- Fever and fatigue;
- Night sweats;
- Unexplained weight loss;
- Enlargement of the chest and abdomen;
- Cough, shortness of breath, and chest pain;
- Enlargement of the spleen (splenomegaly); and
- Itching of the skin (pruritus).
Diagnosis of lymphoma
During the consultation, the doctor inquires about the child’s symptoms, and a physical examination is conducted to check for swollen lymph nodes in areas such as the armpits, neck, and groin. If any are found, tests will be requested to confirm the diagnosis.
Tests are also requested to assess the patient’s overall health and to check for other diseases that may present with symptoms similar to lymphomas.
The other tests usually include:
Lymph node biopsy: the lymph node is surgically removed and sent to the laboratory for analysis. It is the test that confirms whether or not it is lymphoma;
Bone marrow biopsy: when requested, the procedure includes the removal of a small fragment of bone from the iliac crest (pelvis) using a needle to determine if there has been spread to the bone marrow.
Computed tomography (CT) scan: the equipment has a table on which the patient lies down for the exam, which allows the identification of enlarged lymph nodes throughout the body and enables the evaluation of disease spread;
Magnetic resonance imaging (MRI): a method that uses electromagnetic waves to form images, allowing for an evaluation of internal organs. It is used less frequently than CT scans; and
PET scan: allows for the identification of other parts of the body that may be affected by lymphoma and verifies whether the enlarged lymph nodes are diseased or benign. It is also performed to show the response to ongoing treatment.
Treatment of lymphoma in children
Treatment of lymphoma in children and adolescents can have excellent results, with cure rates exceeding 80% considering the extent and initial volume of the tumor mass. Due to its involvement of various parts of the body, surgery or radiation therapy are ineffective even when the disease is localized. The approaches are mainly based on chemotherapy, radiation therapy, stem cell transplants, and immunotherapies. Understand each of them better:
- Chemotherapy – primary therapeutic modality regardless of the location or staging of the disease. The treatment uses medications to destroy, control, and inhibit the growth of cancer cells. It can be administered orally, intravenously through a catheter into the vein, or intrathecally when the medication is injected into the spinal column to reach the central nervous system. Some side effects may occur, such as nausea, diarrhea, constipation, changes in taste, dry mouth, mouth sores, and difficulty swallowing;
- Radiation therapy – used in some cases, with radiation destroying or inhibiting the growth of abnormal cells that form a tumor;
- Bone marrow transplant – also called hematopoietic stem cell transplant, this option is indicated when the treatment is not achieving the desired result. If the bone marrow is not affected, the patient’s own cells will be used for the transplant, in what is called an autologous transplant.
In a surgical setting, stem cells are collected through a vein or by direct bone marrow collection, then frozen and stored (cryopreserved). After collection and cryopreservation, the patient undergoes a regimen of high-dose chemotherapy, called conditioning, which aims to eliminate all cells. This chemotherapy regimen consequently destroys the bone marrow. Therefore, after chemotherapy, the previously collected stem cells are thawed and infused back into the patient.
When the bone marrow starts functioning again (around 2 to 4 weeks after the infusion), it can be said that the marrow has “engrafted”; and
- Immunotherapy – is a treatment carried out with antibodies produced in the laboratory targeted at a specific target of cancer cells. As a result, immunotherapy causes the immune system itself to recognize diseased cells and attack them. Some possible side effects include chills, fever, nausea, rashes, fatigue, and headaches.
Prevention of childhood lymphoma
Most children with lymphoma do not have known risk factors that can be altered – thus, there is no way to protect against lymphomas.
Patients at high risk of developing Hodgkin or non-Hodgkin lymphoma are those with compromised immune systems (immunodeficiencies), HIV infection, Epstein-Barr virus, use of immunosuppressive drugs, and a family history of lymphomas.
