Cowden syndrome (CS) is characterized by multiple tumor-like growths and an increased risk of certain cancers. The majority of patients with CS develop small, non-cancerous growths, or hamartomas, of the skin and mucous membranes, but these growths can also occur in the intestinal tract or brain. Individuals with CS also have an increased risk of developing benign and malignant tumors of the breast, uterus and thyroid. CS is associated with mutations in the PTEN gene.

Hereditary non-polyposis colorectal cancer syndrome (HNPCC) or Lynch Syndrome is characterized by early age onset colorectal cancer and endometrial (uterine) cancer as well as other extracolonic tumors. Hereditary nonpolyposis colorectal cancer (HNPCC) or Lynch Syndrome is caused by mutations in DNA mismatch repair genes (MLH1, MSH2, MSH6 or PMS2). A variant of HNPCC-Lynch Syndrome called Muir Torre Syndrome is associated with increased risk for certain skin tumors. A second variant, called Turcot Syndrome, is associated with certain brain tumors (different than in FAP).

Familial adenomatous polyposis (FAP) or Gardner's Syndrome is a colon cancer predisposition syndrome in which hundreds to thousands of precancerous colon polyps (called adenomas) develop throughout the gastrointestinal tract (mostly in the colon and rectum but also in the stomach and small intestine). Attenuated FAP (AFAP) is a milder form of FAP and is associated with increased risk for colon cancer but fewer number of colon polyps. Gardner's Syndrome is associated with the typical number of polyps as in FAP, but also osteomas (benign tumors of the bone) and soft tissue tumors (called desmoids). A second variant, called Turcot Syndrome, is associated with certain brain tumors (different than in HNPCC-Lynch Syndrome). All forms of FAP are associated with mutations in the APC gene.

Li-Fraumeni Syndrome (LFS) is a rare genetic condition characterized by increased risk to develop multiple types of cancer. The cancers that occur in LFS can be diagnosed during childhood, adolescence or adulthood. Most individuals with LFS are found to have mutations in the TP53 gene.The most common types of cancer associated with LFS include: 

• Soft tissue sarcomas (tumor in fat, muscle, nerve, joint, blood vessel, bone or deep skin)
• Breast cancer
• Leukemia
• Lung cancer
• Brain cancer
• Adrenal gland cancer

Von Hippel-Lindau disease (VHL) is a multi-system disorder characterized by abnormal growth of blood vessels (called hemangioblastomas or angiomas). Hemagioblastomas may develop in the retina, certain areas of the brain, the spinal cord and other parts of the nervous system. Other types of tumors can develop in the adrenal gland, kidney and pancreas. Individuals with VHL also have a higher risk to develop certain types of cancer, especially kidney cancer. Nearly all individuals with VHL are found to have mutations in the VHL gene.

Multiple endocrine neoplasia (MEN) syndromes received their name because they predispose people to develop tumors of the endocrine glands. The endocrine system is comprised of glands that secrete hormones into the bloodstream that control numerous processes within the body. The endocrine system is instrumental in regulating mood, growth and development and metabolism, as well as sexual function and reproductive processes.

The major glands of the endocrine system affected by the MEN syndromes are the pituitary, thyroid, parathyroids, adrenals and pancreas. Currently, there are two distinct MEN syndromes: MEN1 and MEN2. In some ways, the two syndromes are similar, but there are important differences.