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What is Cowden syndrome and explain in detail?
Cowden syndrome (also known as Cowdens disease and multiple hamartoma syndrome) is an autosomal dominant inherited condition characterized by benign overgrowths called hamartomas as well as an increased lifetime risk of breast, thyroid, uterine, and other cancers. It is often underdiagnosed due to variability in disease presentation, but 99% of patients report mucocutaneous symptoms by age 20–29. Despite some considering it a primarily dermatologic condition, Cowdens syndrome is a multi-system disorder that also includes neurodevelopmental disorders such as macrocephaly.The incidence of Cowdens disease is about 1 in 200,000, making it quite rare. Furthermore, early and continuous screening is essential in the management of this disorder to prevent malignancies. It is associated with mutations in PTEN on 10q23.3, a tumor suppressor gene otherwise known as phosphatase and tensin homolog, that results in dysregulation of the mTOR pathway leading to errors in cell proliferation, cell cycling, and apoptosis. The most common malignancies associated with the syndrome are adenocarcinoma of the breast (20%), followed by adenocarcinoma of the thyroid (7%), squamous cell carcinomas of the skin (4%), and the remaining from the colon, uterus, or others (1%).

Signs and symptoms
As Cowdens disease is a multi-system disorder, the physical manifestations are broken down by organ system:
Skin
Adolescent patients affected with Cowden syndrome develop characteristic lesions called trichilemmomas, which typically develop on the face, and verrucous papules around the mouth and on the ears. Oral papillomas are also common. Furthermore, shiny palmar keratoses with central dells are also present. At birth or in childhood, classic features of Cowdens include pigmented genital lesions, lipomas, epidermal nevi, and cafe-au-lait spots. Squamous cell carcinomas of the skin may also occur.Thyroid
Two thirds of patients have thyroid disorders, and these typically include benign follicular adenomas or multinodular goiter of the thyroid. Additionally, Cowdens patients are more susceptible to developing thyroid cancer than the general population. It is estimated that less than 10 percent of individuals with Cowden syndrome may develop follicular thyroid cancer. Cases of papillary thyroid cancer have been reported as well.Female and Male Genitourinary
Females have an elevated risk of developing endometrial cancers, which is highest for those under the age of 50. Currently, it is not clear whether uterine leiomyomata (fibroids) or congenital genitourinary abnormalities occur at an increased rate in Cowden syndrome patients as compared to the general population. The occurrence of multiple testicular lipomas, or testicular lipomatosis, is a characteristic finding in male patients with Cowden syndrome.Gastrointestinal
Polyps are extremely common as they are found in about 95% of Cowden syndrome patients undergoing a colonoscopy. They are numerous ranging from a few to hundreds, usually of the hamartomatous subtype, and distributed across the colon as well as other areas within the gastrointestinal tract. Other types of polyps that may be encountered less frequently include ganglioneuromatous, adenomatous, and lymphoid polyps. Diffuse glycogenic acanthosis of the esophagus is another gastrointestinal manifestation associated with Cowden syndrome.Breast
Females are at an increased risk of developing breast cancer, which is the most common malignancy observed in Cowdens patients. Although some cases have been reported, there is not enough evidence to indicate an association between Cowden syndrome and the development of male breast cancer. Up to 75% demonstrate benign breast conditions such as intraductal papillomatosis, fibroadenomas, and fibrocystic changes. However, there is currently not enough evidence to determine if benign breast disease occurs more frequently in Cowdens patients as compared to individuals without a hereditary cancer syndrome.Central Nervous System
Macrocephaly is observed in 84% of patients with Cowden syndrome. It typically occurs due to an abnormally enlarged brain, or megalencephaly. Patients may also exhibit dolichocephaly. Varying degrees of autism spectrum disorder and intellectual disability have been reported as well. Lhermitte-Duclos disease is a benign cerebellar tumor that typically does not manifest until adulthood in patients with Cowden syndrome.

Genetics
Cowden syndrome is inherited in an autosomal dominant fashion. Germline mutations in PTEN (phosphatase and tensin homolog), a tumor suppressor gene, are found in up to 80% of Cowdens patients. Several other hereditary cancer syndromes, such as Bannayan-Riley-Ruvalcaba syndrome, have been associated with mutations in the PTEN gene as well. PTEN negatively regulates the cytoplasmic receptor tyrosine kinase pathway, which is responsible for cell growth and survival, and also functions to repair errors in DNA. Thus, in the absence of this protein, cancerous cells are more likely to develop, survive, and proliferate.Recently, it was discovered that germline heterozygous mutations in SEC23B, a component of coat protein complex II vesicles secreted from the endoplasmic reticulum, are associated with Cowden syndrome. A possible interplay between PTEN and SEC23B has recently been suggested, given emerging evidence of each having a role in ribosome biogenesis, but this has not been conclusively determined.

Diagnosis
The revised clinical criteria for the diagnosis of Cowdens syndrome for an individual is dependent on either one of the following: 1) 3 major criteria are met or more that must include macrocephaly, Lhermitte-Duclos, or GI hamartomas 2) two major and three minor criteria. The major and minor criteria are listed below:

Screening
The management of Cowden syndrome centers on the early detection and prevention of cancer types that are known to occur as part of this syndrome