Cancer syndrome

A cancer syndrome or family cancer syndrome is a genetic disorder in which inherited genetic mutations in one or more genes predispose the affected individuals to the development of cancers and may also cause the early onset of these cancers. Cancer syndromes often show not only a high lifetime risk of developing cancer, but also the development of multiple independent primary tumors. Many of these syndromes are caused by mutations in tumor suppressor genes, genes that are involved in protecting the cell from turning cancerous. Other genes that may be affected are DNA repair genes, oncogenes and genes involved in the production of blood vessels (angiogenesis). Common examples of inherited cancer syndromes are hereditary breast-ovarian cancer syndrome and hereditary non-polyposis colon cancer (Lynch syndrome).sebaceous adenomas) A cancer syndrome or family cancer syndrome is a genetic disorder in which inherited genetic mutations in one or more genes predispose the affected individuals to the development of cancers and may also cause the early onset of these cancers. Cancer syndromes often show not only a high lifetime risk of developing cancer, but also the development of multiple independent primary tumors. Many of these syndromes are caused by mutations in tumor suppressor genes, genes that are involved in protecting the cell from turning cancerous. Other genes that may be affected are DNA repair genes, oncogenes and genes involved in the production of blood vessels (angiogenesis). Common examples of inherited cancer syndromes are hereditary breast-ovarian cancer syndrome and hereditary non-polyposis colon cancer (Lynch syndrome). Hereditary cancer syndromes underlie 5 to 10% of all cancers and there are over 50 identifiable hereditary forms of cancer. Scientific understanding of cancer susceptibility syndromes is actively expanding: additional syndromes are being found, the underlying biology is becoming clearer, and commercialization of diagnostic genetics methodology is improving clinical access. Given the prevalence of breast and colon cancer, the most widely recognized syndromes include hereditary breast-ovarian cancer syndrome (HBOC) and hereditary non-polyposis colon cancer (HNPCC, Lynch syndrome). Some rare cancers are strongly associated with hereditary cancer predisposition syndromes. Genetic testing should be considered with adrenocortical carcinoma; carcinoid tumors; diffuse gastric cancer; fallopian tube/primary peritoneal cancer; leiomyosarcoma; medullary thyroid cancer; paraganglioma/pheochromocytoma; renal cell carcinoma of chromophobe, hybrid oncocytic, or oncocytoma histology; sebaceous carcinoma; and sex cord tumors with annular tubules. Primary care physicians can identify people who are at risk of heridatary cancer syndrome. Two copies of every gene are present in all cells of the body and each one is called an allele. Most cancer syndromes are transmitted in a mendelian autosomal dominant manner. In these cases, only one faulty allele has to be present for an individual to have a predisposition to cancer. Individuals with one normal allele and one faulty allele are known as heterozygous. A heterozygous individual and a person with two normal alleles (homozygous) will have a 50% chance of producing an affected child. The mutation in the inherited gene is known as a germline mutation and a further mutation in the normal allele results in the development of cancer. This is known as Knudson's two hit hypothesis, where the first hit of the gene is the inherited mutation and the second hit occurs later in life. As only one allele needs to be mutated (as compared to both in so-called 'sporadic cancers'), the individual has a higher chance of developing the cancer than the general population. Less often, syndromes may be transmitted as an autosomal recessive trait. Both alleles of a gene must be mutated in autosomal recessive disorders for an individual to have a predisposition to cancer. A person with two recessive alleles is known as homozygous recessive. Both parents must have at least one faulty allele in order for a child to be homozygous recessive. If both parents have one mutant allele and one normal allele (heterozygous) then they have a 25% chance of producing a homozygous recessive child (has predisposition), 50% chance of producing a heterozygous child (carrier of the faulty gene) and 25% chance of produced a child with two normal alleles. Examples of autosomal dominant cancer syndromes are autoimmune lymphoproliferative syndrome (Canale-Smith syndrome), Beckwith–Wiedemann syndrome (although 85% of cases are sporadic), Birt–Hogg–Dubé syndrome, Carney syndrome, familial chordoma, Cowden syndrome, dysplastic nevus syndrome with familial melanoma, familial adenomatous polyposis, hereditary breast-ovarian cancer syndrome, hereditary diffuse gastric cancer (HDGC), hereditary non-polyposis colon cancer (Lynch syndrome), Howel–Evans syndrome of eosophageal cancer with tylosis, juvenile polyposis syndrome, Li-Fraumeni syndrome, multiple endocrine neoplasia type 1/2, multiple osteochondromatosis, neurofibromatosis type 1/2, nevoid basal cell carcinoma syndrome (Gorlin syndrome), Peutz-Jeghers syndrome, familial prostate cancer, hereditary leiomyomatosis renal cell cancer (LRCC), hereditary papillary renal cell cancer (HPRCC), hereditary paraganglioma-pheochromocytoma syndrome, retinoblastoma, tuberous sclerosis, von Hippel-Lindau disease and Wilm's tumor. Examples of autosomal recessive cancer syndromes are ataxia telangiectasia, Bloom syndrome, Fanconi anemia, MUTYH-associated polyposis, Rothmund-Thomson syndrome, Werner's syndrome and Xeroderma pigmentosum.