Pediatric Tumors

• Among children (0-14 years) and adolescents (0-19 years) in the US, cancer is the second most common cause of death, following injury-related deaths, and the leading cause of death by disease.
• The case distribution by International Classification of Childhood Cancer (ICCC) cancer types is leukemias (28% and 13% in children and adolescents, respectively), followed by central nervous system neoplasms (27%, 21%), lymphomas (12%, 19%), neuroblastoma and other peripheral nervous cell tumors (6%, <1%),  nephroblastoma and other nonepithelial renal tumors (5%, <1%), malignant bone tumors (4%, 5%), rhabdomyosarcoma (3%), germ cell and gonadal tumors (3%), hepatic tumors (2%, <1%), retinoblastoma (2%, <1%), thyroid carcinoma (2%, 11%), and malignant melanoma (1%, 3%).
• The overall cancer incidence in children and adolescents has increased (by 0.6-0.7% per year).
• The mortality rates have decreased from 6.3 and 7.1/100,000 children and adolescents in 1970 to 2.0 and 2.9/100,000 in 2018, respectively, which were 68% and 59% reductions.
  • However, the survival rates remain low for some tumor types (e.g., diffuse intrinsic pontine glioma), for some age groups (e.g., Wilms tumors in older patients), tumors in higher stages (metastasis), and tumors with unfavorable histology (e.g., neuroblastoma, Wilms tumor).

Pediatric Extracranial Solid Tumors

• Pediatric cancers are divided into three broad groups: hematologic, central nervous system (CNS) tumors, and extracranial solid tumors (EST).
• Extracranial solid tumors account for approximately 40% of all pediatric cancers.
• Pediatric EST is roughly subdivided into two groups:
  • Mesenchymal-derived tumors (sarcomas) in bone and soft tissue and less commonly in other organs
    • Pediatric sarcomas often show monotonous “small round cell tumor” or “spindle cell tumor” morphology resembling each other.
  • Embryonal to predominantly epithelial-type tumors with morphologic features following the embryonic differentiation specific to the organs; many of these tumors are called “-blastomas.”
    • Typical histologic features of “-blastomas” are helpful for correct diagnosis.
• The diagnosis is challenging solely by histology and usually requires ancillary testing, such as immunohistochemical staining and molecular testing.

References

1. Bleyer, A., A. Viny, and R. Barr, Cancer in 15- to 29-year-olds by primary site. Oncologist, 2006. 11(6): p. 590-601.
2. Siegel, R.L., et al., Cancer Statistics, 2021. CA Cancer J Clin, 2021. 71(1): p. 7-33.
3. Hayat, M.J., et al., Cancer statistics, trends, and multiple primary cancer analyses from the Surveillance, Epidemiology, and End Results (SEER) Program. Oncologist, 2007. 12(1): p. 20-37.