Central nervous system (CNS) cancers are the second most frequent in pediatric oncology, accounting for about 27% of CC [2]. in children under 15 years of age. Childhood cancers (CC) include a variety of malignant tumors. Annual incidence worldwide is approximately 160,000 cases per year, whereas mortality rates average 90,000 [1]. Leukemia is diagnosed in about 30 34% of all CC [1]. Acute lymphoblastic leukemia (ALL) and acute myeloblastic leukemia (AML) are the two most frequent types of leukemia found in children [1]. The former occurs approximately five times more frequently than the latter, and accounts for approximately 75% of all childhood leukemia cases [1]. Central nervous system (CNS) cancers are the AZD1208 second most frequent in pediatric oncology, accounting for about 27% of CC [2]. The occurrence of CNS tumor types in children differs by type, with 30% low-grade glioma, 25% medulloblastoma, 20% high-grade glioma, 10% atypical teratoid/rhabdoid tumor, and 15% other CNS tumors [3]. Lymphomas represent the next most common type of CC, averaging 15% [4]. According to the National Cancer Institute, Hodgkins lymphoma (HL) accounts for 4 6% of all childhood cancers, with the highest incidence rates in 1519 year olds [2]. Non-Hodgkins lymphomas (NHL) account for 6 7% of all childhood malignancies, and are comprised of the four most frequent subtypes, Burkitts lymphoma (BL), lymphoblastic lymphoma (LL), diffuse large B-cell lymphoma (DLBCL), AZD1208 and anaplastic large cell lymphoma (ALCL) [4]. There are other subtypes of childhood NHL, but they account for less than 5% of all cases. Incidence statistics for soft tissue cancers is around 9%, whereas for bone cancers (including osteosarcoma and Ewings sarcoma) the incidence is 6% [2]. Neuroblastoma is diagnosed in 7% of the CC cases, nephroblastoma (Wilms) tumors occurs in 5% and retinoblastoma in 3% CC cases [2]. Cancers found in children are usually quite distinct from those seen in adults. Because the causes of childhood cancers are unknown, it is difficult to determine a specific mechanism. This may be due to different exposures to environmental hazards/infectious agents coupled with immature physiological systems, as well as vulnerability at critical developmental stages [5]. In this review, we address the possible role of infectious agents AZD1208 in the onset and progression of childhood tumors. Our search strategies included AZD1208 a background literature review, then systematic analysis and all-round discussion of found information on childhood cancers, risk factors and mechanisms of infectious agents. General and advanced search via the most comprehensive scientific databases on life sciences and biomedical topics, such as MEDLINE and SpringerLink, were used to conduct effective literature review. The search specifications narrowed species to Human, language to English and article types to Review, clinical, trials, meta-analyses, and case reports. Reference lists were thereafter hand-searched for additional articles. Then the full text articles were obtained and analyzed for actuality and authenticity of information. == Possible causes and risk factors == To date, in addition to inherited factors, the World Health Organization (WHO) classifies four different groups of external agents as carcinogens which cause cancer in children. These are physical, biological, chemical carcinogens, and dietary components (e.g., cured meats) [5]. Extensive data is now available on known and suspected risk factors for childhood cancers, including but not limited to: early-life exposures to infectious agents (viruses, bacteria, protozoa, and fungi); parental, fetal, or childhood exposures to environmental toxins (pesticides, solvents, and household chemicals); parental occupational exposures to radiation or chemicals; parental medical conditions during pregnancy or before conception; maternal diet during pregnancy; early postnatal feeding patterns AZD1208 and diet; maternal reproductive history, and familial and genetic susceptibility; and risk associated with exposure to HIV[5]. Genetic risk factors usually include familial aggregations of genetic syndromes such as retinoblastoma, Li-Fraumeni syndrome, hereditary nonpolyposis colon cancer, ataxia telangiectasia, and others [6]. However, there are still no definitive causes identified for CC. In general, in 5 15% of CC cases genetic factors are thought to predispose the child to the development of cancer [7]. Environmental and exogenous factors have HNRNPA1L2 much lower figures (5 10%), leaving the vast majority of CC (75 90%) poorly recognized and of unfamiliar causes [8,9]. Because malignancy is definitely a multifactorial disease caused by genetic and environmental factors, it is often hard to determine the critical period of exposure as during pregnancy.
