PTEN Gene

Cowden syndrome is a genetic disorder characterized by multiple noncancerous, tumor-like growths called hamartomas and an increased risk of developing certain cancers.

Almost everyone with Cowden syndrome develops hamartomas. These growths are most commonly found on the skin and mucous membranes (such as the lining of the mouth and nose), but they can also occur in the intestine and other parts of the body. The growth of hamartomas on the skin and mucous membranes typically becomes apparent by a person's late twenties.

Cowden syndrome is associated with an increased risk of developing several types of cancer, particularly cancers of the breast, a gland in the lower neck called the thyroid, and the lining of the uterus (the endometrium). Other cancers that have been identified in people with Cowden syndrome include kidney cancer, colorectal cancer, and an agressive form of skin cancer called melanoma. Compared with the general population, people with Cowden syndrome develop these cancers at younger ages, often beginning in their thirties or forties. People with Cowden syndrome are also more likely to develop more than one cancer during their lifetimes compared to the general population. Other diseases of the breast, thyroid, and endometrium are also common in Cowden syndrome. Additional signs and symptoms can include an enlarged head (macrocephaly) and a rare, noncancerous brain tumor called Lhermitte-Duclos disease. A small percentage of affected individuals have delayed development, intellectual disability, or autism spectrum disorder, which can affect communication and social interaction.

Some people do not meet the strict criteria for a clinical diagnosis of Cowden syndrome, but they have some of the characteristic features of the condition, particularly the cancers. These individuals are often described as having Cowden-like syndrome. Both Cowden syndrome and Cowden-like syndrome are caused by mutations in the same genes.

The features of Cowden syndrome overlap with those of another disorder called Bannayan-Riley-Ruvalcaba syndrome. People with Bannayan-Riley-Ruvalcaba syndrome also develop hamartomas and other noncancerous tumors.  Some people with Cowden syndrome have relatives diagnosed with Bannayan-Riley-Ruvalcaba syndrome, and other affected individuals have the characteristic features of both conditions. Based on these similarities, researchers have proposed that Cowden syndrome and Bannayan-Riley-Ruvalcaba syndrome represent a spectrum of overlapping features known as PTEN hamartoma tumor syndrome (named for the genetic cause of the conditions) instead of two distinct conditions.

MN1 C-terminal truncation (MCTT) syndrome is a condition characterized by intellectual disability, developmental delay, distinctive facial features, and brain abnormalities.

Most people with MCTT syndrome have mild to moderate intellectual disability. Many affected individuals are nonverbal, but some have speech limited to one or two words or communicate using sign language. Most children with this condition have delayed development of motor skills, such as crawling or walking, but are able to walk by age 2 or 3. However, they often need help with fine-motor skills, such as getting dressed or using a fork when eating.

Individuals with MCTT syndrome often have distinctive facial features that include a sunken appearance of the middle of the face (midface hypoplasia); a high arch in the roof of the mouth (high-arched palate); outside corners of the eyes that point downward (downslanting palpebral fissures); widely spaced eyes (hypertelorism ); shallow and bulging eyes (exophthalmos); a short, upturned nose; and small, low-set ears. Some affected individuals have dental abnormalities, such as cone-shaped (conical ), jagged, or crowded teeth. Rarely, people with MCTT syndrome have premature fusion of certain skull bones (craniosynostosis).

People with MCTT syndrome often have characteristic brain abnormalities. The surface of the brain normally has many ridges or folds, called gyri. A common brain abnormality in people with MCTT syndrome is called perisylvian polymicrogyria, in which an area of the brain called the perisylvian region develops too many gyri, and the folds are irregular and unusually small. Individuals with MCTT syndrome can also have a malformation of the part of the brain that coordinates movement (the cerebellum ). This malformation, called atypical rhombencephalosynapsis, is characterized by tissue loss in the central part of the cerebellum (known as the vermis) and fusion of the two sides of the cerebellum. These brain abnormalities likely contribute to the movement problems and intellectual disability that are common in MCTT syndrome. 

Less common features of MCTT syndrome include hearing loss, seizures, abnormal curvature of the spine, and heart abnormalities.

Breast cancer is a disease in which certain cells in the breast become abnormal and multiply uncontrollably to form a tumor. Although breast cancer is much more common in women, this form of cancer can also develop in men. In both women and men, the most common form of breast cancer begins in cells lining the milk ducts (ductal cancer). In women, cancer can also develop in the glands that produce milk (lobular cancer). Most men have little or no lobular tissue, so lobular cancer in men is very rare.

In its early stages, breast cancer usually does not cause pain and may exhibit no noticeable symptoms. As the cancer progresses, signs and symptoms can include a lump or thickening in or near the breast; a change in the size or shape of the breast; nipple discharge, tenderness, or retraction (turning inward); and skin irritation, dimpling, redness, or scaliness. However, these changes can occur as part of many different conditions. Having one or more of these symptoms does not mean that a person definitely has breast cancer.

In some cases, cancerous cells can invade surrounding breast tissue. In these cases, the condition is known as invasive breast cancer. Sometimes, tumors spread to other parts of the body. If breast cancer spreads, cancerous cells most often appear in the bones, liver, lungs, or brain. Tumors that begin at one site and then spread to other areas of the body are called metastatic cancers.

A small percentage of all breast cancers cluster in families. These cancers are described as hereditary and are associated with inherited gene mutations. Hereditary breast cancers tend to develop earlier in life than noninherited (sporadic) cases, and new (primary) tumors are more likely to develop in both breasts.