Lymphoma represents the third most common pediatric cancer in children between the ages of 0 and 19 years. Sixty percent of all childhood and adolescent lymphomas are classified as non-Hodgkin lymphoma (NHL). NHL represents approximately 10% of all malignancies that occur in children and adolescents. Between 1975 and 2010, the 5-year survival rate for NHL increased from 45% to 87% in children younger than 15 years and from 48% to 82% for adolescents aged 15 to 19 years.
PATHOGENESIS AND EPIDEMIOLOGY
NHL occurs most commonly in the second decade of life, and occurs infrequently in children younger than 3 years. The incidence of childhood NHL is more common in males than in females and is higher in whites than in nonwhites. Risk factors for the development of NHL in children and adolescents are largely unknown, except that children with either inherited and/or acquired immunodeficiencies have a significantly increased risk for developing NHL.
As opposed to NHL seen in adults, where indolent and intermediate subtypes predominate, over 95% of childhood and adolescent NHL are intermediate or aggressive subtypes. Types of childhood NHL according to World Health Organization (WHO) classification are (1) mature B-cell lymphoma, including Burkitt lymphoma (BL; 40% of pediatric NHL) and diffuse large B-cell lymphoma (DLBCL) and variants (15%), and (2) mature T- and natural killer (NK)-cell lymphomas, including anaplastic large-cell lymphoma (ALCL; 15%). Lymphoblastic lymphoma (LL; 20%) is classified with its precursor acute lymphoblastic leukemia (ALL) in the WHO classification. The other 10% of cases of NHL observed in childhood include lymphoproliferative disease in immunodeficient patients, indolent B-cell lymphoma, and other mature T-cell lymphomas.
Less than 10% of childhood and adolescent cases of NHL presents in peripheral nodal tissue. The majority will present with extranodal disease, including lymphoid tissue of the head and neck or gastrointestinal tract. Other presenting sites include the liver, spleen, bone marrow, cerebrospinal fluid, skin, bone, gonads, or central nervous system (CNS). The most common sites of presentation include the head and neck (30%), abdomen (30%), and mediastinal and/or hilar lymph nodes (30%). Each pathologic subtype has distinct primary organ sites of presentation as outlined in Table 447-1.
TABLE 447-1CHILDHOOD AND ADOLESCENT NON-HODGKIN LYMPHOMA: CLINICAL AND PATHOLOGIC CHARACTERISTICS AND OUTCOME ||Download (.pdf) TABLE 447-1CHILDHOOD AND ADOLESCENT NON-HODGKIN LYMPHOMA: CLINICAL AND PATHOLOGIC CHARACTERISTICS AND OUTCOME
|Histologic Subtype ||Percent Observed ||Immunophenotype ||Anatomic Presentation ||Survival |
|Burkitt lymphoma ||40% ||B-cell (100%) ||Abdomen, lymph nodes, head and neck, BM, CNS || |
Diffuse large B-cell lymphoma (DLBCL)
|15% ||B-cell (100%) ||Lymph nodes, mediastinum || |
Anaplastic large-cell lymphoma (ALCL)
|15% || |
|Lymph nodes, skin, liver, spleen, mediastinum || |
Lymphoblastic lymphoma (LL)
|20% || |
|Mediastinum, lymph nodes, BM, ...|