Non-Hodgkin Lymphoma

Kenneth L. McClain

EPIDEMIOLOGY

Non-Hodgkin lymphomas (NHLs) represent 6% of all tumors in the pediatric age group and are the fifth most frequent. The incidence per million children is 8.5 for those less than 15 years and 17.1 for children 15 to 19 years of age, with a slight male predominance and 1.5 times as many white patients as black. Three major histologic varieties exist—lymphoblastic lymphoma (LL), Burkitt lymphoma (BL), and large cell lymphomas—most of which are considered high grade. Patients with congenital or acquired immunodeficiency (including those with human immunodeficiency virus infection and transplant recipients) are at higher risk for developing lymphomas than the physiologically normal population. There is a statistically significant association for all subtypes of NHL with maternal pesticide exposure when the patient with lymphoma was in utero.

CLINICAL MANIFESTATIONS

Lymphoblastic Lymphoma

LLs make up 30% to 35% of childhood NHLs. For a child with lymphomatous features of massive lymphadenopathy and hepatosplenomegaly, an arbitrary distinction between leukemia and lymphoma is made by evaluating the bone marrow aspirate. If fewer than 25% lymphoblasts exist in the marrow, the diagnosis is lymphoma; if more than 25%, the diagnosis is acute lymphoblastic leukemia. The cell of origin usually is a T lymphoblast, especially in patients with stage III or IV disease (Table 305.1). Frequent cytogenetic abnormalities are found in the T-cell receptor gene on the long arm (q11.2) of chromosome 14. The B-precursor immunophenotype is found in one-third of patients with stage I and II disease, but in fewer than 5% of patients with a higher stage.

Most children present with painless cervical lymphadenopathy, a mediastinal mass, and moderate hepatosplenomegaly. Fevers and weight loss are less common than in Hodgkin disease, but they are an unfavorable prognostic sign if present. An anterior mediastinal mass with or without a pleural effusion may cause respiratory compromise or the superior vena cava syndrome, and either can be a true medical emergency. These patients should not be forced to lie flat because their airway may obstruct. A high incidence of central nervous system involvement and leukemic transformation exists in patients with LL.

Burkitt Lymphoma

BL is the most common of NHL in childhood (40% to 50%). Patients usually present with an abdominal mass that may originate in the bowel, kidneys, or gonads and may be accompanied by massive ascites. BL is a particularly dangerous form of childhood cancer because it is a rapidly growing tumor that masquerades as an apparently benign case of tonsillitis or as an intussusception from a leading enlargement of cecal, ileal, or mesenteric nodes (Fig. 305.1). Bone marrow involvement may show the L3 variety of lymphoblast, containing many vacuoles.

Immunophenotyping studies reveal tumor cells of a mature B-cell phenotype with surface immunoglobulin. The classic translocation of chromosomes 8 and 14 juxtaposing the
c-myc oncogene (8q24.1) and an immunoglobulin heavy-chain promoter (14q32) are found in more than 80% of cases. Alternative immunglobulin light-chain-myc transolocations t2;8 or t8;22 account for nearly 20% of cases. Additional cytogenetic abnormalities including duplications of chromosome 1, especially bands q21-23, are found in 30% of cases.

TABLE 305.1. STAGING OF CHILDHOOD NON-HODGKIN LYMPHOMA

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