Childhood Lymphoma
Summary of Key Points
Incidence
• Malignant lymphoma, which comprises both Hodgkin lymphoma and non-Hodgkin lymphoma (NHL), is the third most common malignancy in childhood.
• Among children younger than age 15 years, there is a slight predominance of NHL, whereas HL is more frequent among children up to age 18 years.
• There are approximately 500 newly diagnosed cases of pediatric NHL in the United States each year.
Etiology/Epidemiology
• NHL is more common in boys than girls and in white children than black.
• There are geographic differences with respect to the frequency of histologic subtypes of NHL. Burkitt lymphoma is the predominant subtype in equatorial Africa and northeast Brazil, where it is associated with Epstein-Barr virus in the majority of cases, in contrast to the infrequent association observed in the United States and Western Europe.
• Children with immunodeficiency conditions are at increased risk of developing NHL. These include those with ataxia-telangiectasia (A-T), Wiskott-Aldrich syndrome, and X-linked lymphoproliferative syndrome (XLP). Children with acquired immunodeficiency disorders, including the acquired immunodeficiency syndrome (AIDS), and those receiving immunosuppressive therapy following bone marrow or organ transplantation are also at increased risk.
Pathology/Biology
• The most common subtypes of NHL in children are Burkitt lymphoma, lymphoblastic lymphoma, anaplastic large-cell lymphoma, and diffuse large B-cell lymphoma (including the mediastinal subtype).
• Burkitt lymphoma is a mature B-cell lymphoma of germinal center origin, characterized by a very high proliferation rate, resulting from the activation of the c-myc oncogene as a result of juxtaposition to one of the immunoglobulin genes, through one of three characteristic balanced chromosomal translocations, that is, t(8;14), t(2;8), and t(8;22).
• Lymphoblastic lymphoma is typically of precursor T-cell immunophenotype, and may be associated with reciprocal translocations involving a T-cell receptor gene. Rare cases may be of precursor B-cell lineage.
• Anaplastic large-cell lymphoma is a peripheral (postthymic) T-cell lymphoma, characterized by large anaplastic (“hallmark”) cells expressing CD30 and, in the vast majority of pediatric cases, anaplastic lymphoma kinase (ALK), as a result of a balanced translocation involving the ALK gene, for example, t(2;5).
• Diffuse large B-cell lymphomas are a biologically heterogeneous category of mature B-cell lymphomas of germinal center or postgerminal center origin, composed predominantly of large cells, with a diffuse growth pattern.
