Cancer syndrome

A cancer syndrome is a cluster of different genetic changes that predispose the affected individuals to the development of cancer later in life. Cancer syndromes often show not only a high lifetime risk of developing cancer, but also the development of independent bilateral tumors and unusually early onset of cancers.

Cancers that are caused by genetic predispositions are called hereditary cancers.

Genetics
These changes are usually transmitted in a mendelian autosomal dominant manner, meaning that given one affected parent, each child has a 50-50 chance of receiving the genes that promote cancer.

In such cancer syndromes, there is one germline mutation, which predisposes the individual to the development of the cancer. A further mutation in the second allele results in the development of cancer. 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.

This genetic predisposition is usually transmitted in the autosomal dominant manner, in rare cases it may transmitted as an autosomal recessive trait. Three types of genes may be affected: protooncogenes, tumor suppressor genes or mismatch repair genes. Cancer syndromes often manifest also in relatives and show development of independent multiple tumors, early onset and typical phenotypical combinations.

Examples
Examples of some cancer syndromes include BRCA mutations of the BRCA1 or BRCA2 genes, which predispose to the development of breast and ovarian cancers or the much more rare, but clinically interesting Li-Fraumeni syndrome, in which there is a germline mutation in the p53 gene which predisposes the individual to the development of a wide array of cancers.