Lymphoma is the third most common cancer in children.
Lymphoma is a heterogeneous group of cancers separated into:
- Hodgkin's lymphoma
- Non-Hodgkin's lymphoma
Hodgkin's lymphoma occurs when there is a malignant transformation of lymphocytes, primarily in B lymphocytes. This type of lymphoma is most often localized in the lymph nodes and the spleen.
Hodgkin's lymphoma in children shares some of the same biological aspects as the disease in adults. Characteristic with this disease is the Reed-Sternberg cell (RS) or large Hodgkin cell in an inflammatory environment. RS and Hodgkin cells appear to be resistant to apoptotic stimuli. RS and Hodgkin cells are essential for making the diagnosis of classic Hodgkin's lymphoma.
Hodgkin's lymphoma constitutes 30–40% of lymphoma cases in children and is separated into two groups:
- classic Hodgkin's lymphoma
- nodular lymphocyte-predominant Hodgkin's lymphoma
Classic Hodgkin's lymphoma is separated into 4 subgroups:
- nodular sclerosis
- mixed type
When starting first-line treatment, the goal of treatment is always to cure the disease. When there is recurrence of the disease, cure remains the goal of treatment. Treatment of children with Hodgkin's lymphoma reflects the stage of the disease at the time of diagnosis and varies for different treatment groups. Since the treatment often includes both chemotherapy and radiation, there should be a close collaboration between pediatrician and oncologist in the follow up of these patients. The university hospitals are responsible for this treatment in Norway.
Non-Hodgkin lymphoma occurs in the body's lymphatic cells in the entire body. This cancer type is systemic.
The differences between Non-Hodgkin lymphoma in children and adults are:
- Childhood lymphoma is always a high-grade malignant disease. It grows almost always diffusely, which means the lymphoma cells infiltrate entire lymph node with no preservation of normal architecture.
- A large portion of childhood lymphomas start extranodally, meaning that lymphoma in children occurs in places other than the lymph nodes, such as the tonsils, liver, spleen, thymus, bone, and stomach/bowel .
- Non-Hodgkin lymphoma in children grows rapidly and is almost never chronic in character.
Non-Hodgkin lymphoma constitutes about 60% of all lymphoma cases and is separated into three groups:
- Lymphoblastic lymphoma (mostly T-lineage)
- Large cell lymphoma (mostly B-lineage)
- Large cell anaplastic lymphoma (LCAL)
- Burkitt’s and Burkitt’s-like lymphoma
Non B cell lymphoma
Non B cell lymphoma constitute about 30–40% of Non-Hodgkin lymphoma. Over 90% originate from immature T cells. The most common localizations are the mediastinum, pleura, lymph nodes, and skeleton.
B cell lymphoma
Burkitt’s and Burkitt’s-like lymphoma constitute about 40–50% of Non-Hodgkin lymphoma (9). As many as 90% of these tumors are located intraabdominally.
There are three clinical variations of Burkitt's lymphoma (8):
- Immune defect associated Burkitt's lymphoma observed in HIV patients, usually as the first manifestation of AIDS.
- Sporadic Burkitt's lymphoma occurs all over the world, mainly in children and young adults and usually involves the intraabdominal and head/neck regions.
- Endemic Burkitt's lymphoma occurs mainly in parts of Africa and Papua New Guinea. The jaw area is the most common area of invasion.
Burkitt's-like lymphoma is characterized by a larger degree of pleomorphism in cell size and form than observed in classic Burkitt's tumors.
Large cell anaplastic lymphoma
Large cell anaplastic lymphoma constitutes about 10% of all Non-Hodgkin lymphomas in children and can have T cell, B cell, or unknown immunophenotype. It is characterized by a translocation between chromosomes 2 and 5-t(2;5).
In children, these immunophenotypes (most are T immunophenotype ?) occur in similar frequencies. The most common localizations are the mediastinum, lymph nodes, skin, skeleton, and lungs.
In Norway in 2012, in the age group of 0–14 years, there were 8 children who received the diagnosis Hodgkin's lymphoma. There were 6 boys and 2 girls. 12 children received a Non-Hodgkin's diagnosis, 5 boys and 7 girls (13).
Hodgkin's lymphoma has two peaks in incidence: one in the adolescent years and one late in life. Hodgkin's lymphoma is very uncommon in children under 5 years. The incidence increases gradually with age, and is most common in boys.