[Pediatric neoplasms]

The types and frequencies of pediatric neoplasms vary with age, sex, ethnicity, socioeconomic status, and geographic location. The pathogenesis of cancer in children and adult is different. Histopathologic and cytologic diagnosis of pediatric neoplasms can be difficult because they are frequently so anaplastic. For this reason initial aspiration, biopsy or resection of children's cancers need to be conducted in a Children's Cancer Study Group where morphologists have continuous intensive experience with pediatric neoplasms and are prepared to use electron microscopy, cytochemistry, cell surface marker, immunofluorescence and tissue culture methods. Special diagnostic problems on pediatric neoplasms such as transient leukemia (transient myeloproliferative syndrome) or acute megakaryoblastic leukemia in Down syndrome, and reactive or neoplastic histiocytosis are discussed.