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INTRODUCTION

Children and adolescents develop different types of cancers than adults. The 5-year survival rate for all childhood (0 to 19 years of age) cancers in the United States has been steadily increasing and is currently 83% to 84%1; however, malignant neoplasms remain the second leading cause of death for U.S. children age 5 to 14 years.2 The most common childhood malignancies are discussed below.

LEUKEMIA

EPIDEMIOLOGY

Acute leukemias, including acute lymphoblastic leukemia (ALL) and acute myelogenous leukemia (AML), are the most common cancers in children, accounting for over a quarter of all malignancies.3-6 Chronic leukemias are rare in children and adolescents. ALL accounts for approximately 75% to 80% of pediatric leukemias and, if diagnosed early, carries a 5-year survival rate of 85% to 90% in developed countries.4-7 The peak incidence of ALL is 3 to 5 years of age, with younger children having the best outcomes.8 In the United States, ALL is more common in boys and more common in white and Hispanic children than in African American children.2-5 A number of inherited risk factors, including trisomy 21, are well documented.

AML accounts for approximately 15% to 20% of childhood and adolescent leukemias in the United States.4,6,9 Cure rates have improved to 57% to 70% but remain lower than those for ALL. Relapsed AML accounts for greater than half of all childhood leukemia-related deaths.4,9 Incidence of AML peaks in the first 2 years of life.4,6 Environmental exposures, including chemotherapy agents and radiation received during treatment of other childhood cancers, are known causes of secondary AML. Patients being treated for AML have a higher incidence of complications than those with ALL, especially infections. This is primarily due to the greater intensity of chemotherapeutic regimens necessary to achieve remission.

CLINICAL FEATURES

Most signs and symptoms of acute leukemia are due to bone marrow infiltration by blasts, as well as infiltration of extramedullary sites. A detailed history may reveal nonspecific constitutional symptoms: fever, fatigue, anorexia, and weight loss. Cytopenias from marrow infiltration can present as pallor, easy bleeding/bruising with petechiae and ecchymoses, infections, or bone pain. The reticuloendothelial system is the most common site of extramedullary infiltration, manifesting as hepatomegaly, splenomegaly, and/or lymphadenopathy. Other sites include the CNS and testes.

Consider leukemia in cases of recurrent or severe unexplained epistaxis or other mucosal bleeding or in children with unusually extensive or abnormally located bruising. Concerning symptoms include abnormal blood counts, a history of nighttime pain, and recurrent or persistent bony complaints.10 Bone and joint pain may present as limping or refusal to walk. In rare cases of AML, solid nodules of leukemic blasts (chloromas) may be noted, most commonly in the skin (leukemia cutis) or gingiva. For a subset of ...

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