The risks associated with this syndrome include a strong tendency of developing cancer in a number of parts of the body. While the hamartomatous polyps themselves only have a small malignant potential (<3% - OHCM), patients with the syndrome have an increased risk of developing carcinomas of the pancreas, liver, lungs, breast, ovaries, uterus, testicles and other organs.

The average age of first diagnosis is 23, but the lesions can be identified at birth by an astute pediatrician or family physician. Prior to puberty, the mucocutaneous lesions can be found on the palms and soles. Often the first presentation is a bowel obstruction from an intussusception which is a common cause of mortality; an intussusception is a telescoping of one loop of bowel into another segment.

Polyps are most frequent in the stomach and large intestine, are also found in the small intestine, and are least frequent in the esophagus. A biopsy will reveal them to be hamartomas; the possibility that they progress to cancer is generally considered to be low, although it has been reported multiple times in the past. Chronic diarrhea and protein-losing enteropathy are often observed. Possible collateral features include variable anomalies of ectodermal tissues, such as alopecia, atrophy of the nails, or skin pigmentation

Peutz–Jeghers syndrome (often abbreviated PJS) is an autosomal dominant genetic disorder characterized by the development of benign hamartomatous polyps in the gastrointestinal tract and hyperpigmented macules on the lips and oral mucosa (melanosis). This syndrome can be classed as one of various hereditary intestinal polyposis syndromes and one of various hamartomatous polyposis syndromes. It has an incidence of approximately 1 in 25,000 to 300,000 births.

Most patients with fundic gland polyps (FGPs) do not have any symptoms, and the diagnosis is made on gastroscopy done for other reasons. Retrospective analysis of patients with sporadic FGPs shows that a high percentage do have symptoms, but that this is more likely to be related to the underlying disease responsible for the polyposis. These symptoms include:

- epigastric pain

- nausea

- vomiting

- weight loss

The polyps on endoscopy are usually tiny, numerous and sessile, and usually scattered throughout the fundus of the stomach, where parietal cells are more numerous. They have the same colour as the gastric mucosa, and never have a stalk.

When the polyps are biopsied, the pathology typically shows shortened gastric pits, and both superficial and deep cystic lesions in the fundic glands, lined by all three types of cells of acid-producing mucosa: mucous, parietal and chief cells. As sometimes parietal cell hyperplasia may develop deep dilations of gland, one should be really strict in the diagnosis of FGPs (i.e. the presence of deep and superficial dilations). Infrequently, the two lesions may coexist. Foci of dysplasia can sometimes be seen.

Bannayan–Riley–Ruvalcaba syndrome is associated with enlarged head and benign mesodermal hamartomas (multiple hemangiomas, and intestinal polyps). Dysmorphy as well as delayed neuropsychomotor development can also be present. The head enlargement does not cause widening of the ventricles or raised intracranial pressure; these individuals have a higher risk of developing tumors, as the gene involved in BRRs is phosphatase and tensin homologue.

Some individuals have thyroid issues consistent with multinodular goiter, thyroid adenoma, differentiated non-medullary thyroid cancer,

most lesions are slowly growing. Visceral as well as intracranial involvement may occur in some cases, and can cause bleeding and symptomatic mechanical compression

Cronkhite–Canada syndrome is a rare syndrome characterized by multiple polyps of the digestive tract. It is sporadic (i.e. it does not seem to be a hereditary disease), and it is currently considered acquired and idiopathic (i.e. cause remains unknown).

About two-thirds of patients are of Japanese descent and the male to female ratio is 2:1. It was characterized in 1955.

Muir–Torre syndrome (MTS) is a rare hereditary, autosomal dominant cancer syndrome that is thought to be a subtype of HNPCC. Individuals are prone to develop cancers of the colon, genitourinary tract, and skin lesions, such as keratoacanthomas and sebaceous tumors. The genes affected are MLH1, MSH2, and more recently, MSH6, and are involved in DNA mismatch repair.

Fundic gland polyposis is a medical syndrome where the fundus and the body of the stomach develop many polyps. The condition has been described both in patients with familial adenomatous polyposis (FAP) and attenuated variants (AFAP), and in patients in whom it occurs sporadically.

Muir–Torre syndrome is characterized by both:

1. At least a single sebaceous gland tumor (either an adenoma, an epithelioma, or a carcinoma)

2. A minimum of one internal malignancy

The Amsterdam criteria are frequently used to diagnose Lynch syndrome and Muir–Torre syndrome. They include the following:

- 3 or more relatives with an HNPCC-associated cancer (i.e., colorectal, cancer of the endometrium, small bowel, ureter, or renal pelvis)

- 2 or more successive generations affected by cancer

- 1 or more persons with cancer is a first-degree relative of the other 2, at least 1 case of colorectal cancer younger than age 50 years, a diagnosis of familial adenomatous polyposis has been excluded, tumors are verified by histologic examination

Muir–Torre syndrome is a genetic condition. Mutations in MLH1 and MSH2 are linked with the disease. These genes code for DNA mismatch repair genes, and mutations increase the risk of developing cancerous qualities.

Many patients who have sebaceous neoplasms with mutations in MSH2 and MLH1 do not in fact have Muir–Torre syndrome. The Mayo Muir–Torre risk score was devised to improve the positive predictive value of immunohistochemistry and reduce the false positive rate.

The Mayo Muir–Torre Risk score assigns points based several characteristics. A score of 2 or greater has a high positive predictive value of Muir–Torre syndrome. A score of 1 or lower is less likely to be Muir–Torre syndrome.

Age of onset of first sebaceous neoplasm: <60 years = 1 point, otherwise 0 points

Total number of sebaceous neoplasms: 1 = 0 points, >2 = 2 points.

Personal history of Lynch related cancers: No = 0 points, Yes = 1 point

Family history of Lynch-related cancer: No = 0 points, Yes = 1 point

The most common internal malignancies associated with Muir–Torre syndrome are: Colorectal (56%), Urogenital (22%), Small Intestine (4%), and Breast (4%). A variety of other internal malignancies have been reported.

Age of onset is variable. The term 'Juvenile' in the title of Juvenile polyposis syndrome refers to the histological type of the polyps rather than age of onset.

Affected individuals may present with rectal bleeding, abdominal pain, diarrhea or anemia. On colonoscopy or sigmoidoscopy polyps that vary in shape or size are present. The polyps can be sessile or pedunculated hamartomatous polyps.

Juvenile polyposis syndrome is a syndrome characterized by the appearance of multiple juvenile polyps in the gastrointestinal tract. Polyps are abnormal growths arising from a mucous membrane. These usually begin appearing before age 20, but the term "juvenile" refers to the type of polyp, not to the age of the affected person. While the majority of the polyps found in Juvenile Polyposis Syndrome are non-neoplastic, hamartomatous, self-limiting and benign, there is an increased risk of adenocarcinoma.

Solitary juvenile polyps most commonly occur in the rectum and present with rectal bleeding. The World Health Organization criteria for diagnosis of juvenile polyposis syndrome are one of either:

1. More than five juvenile polyps in the colon or rectum; or

2. Juvenile polyps throughout the gastrointestinal tract; or

3. Any number of juvenile polyps in a person with a family history of juvenile polyposis.

Bannayan–Riley–Ruvalcaba syndrome (BRRS) is a rare overgrowth syndrome and hamartomatous disorder with occurrence of multiple subcutaneous lipomas, macrocephaly and hemangiomas. The disease is inherited in an autosomal dominant manner.

The disease belongs to a family of hamartomatous polyposis syndromes, which also includes Peutz–Jeghers syndrome, juvenile polyposis and Cowden syndrome. Mutation of the PTEN gene underlies this syndrome, as well as Cowden syndrome, Proteus syndrome, and Proteus-like syndrome, these four syndromes are referred to as PTEN Hamartoma-Tumor Syndromes.

From early adolescence, patients with this condition gradually (and much of the time 'silently') develop hundreds to thousands of colorectal polyps (and sometimes polyps elsewhere)—small abnormalities at the surface of the intestinal tract, especially in the large intestine including the colon or rectum. These may bleed, leading to blood in the stool. If the blood is not visible, it is still possible for the patient to develop anemia due to gradually developing iron deficiency. If malignancy develops, this may present with weight loss, altered bowel habit, or even metastasis to the liver or elsewhere. FAP can also develop 'silently' in some individuals, giving few or no signs until it has developed into advanced colorectal cancer.

Because familial polyposis develops very gradually over years, and can also manifest in an 'attenuated' form even more gradually, polyps resulting from FAP can lead to cancer developing at any point from adolescence to old age.

Depending on the nature of the defect in the APC gene, and whether it is the full or attenuated form, familial polyposis may manifest as polyps in colon or in the duodenal tract, or in any combination of these. Therefore, an absence of polyps in, for example, the rectum, may not of itself be sufficient to confirm absence of polyps. It may be necessary to consider and visually examine other possible parts of the intestinal tract. Colonoscopy is preferred over sigmoidoscopy for this, as it provides better observation of the common right-side location of polyps.

The genetic determinant in familial polyposis may also predispose carriers to other malignancies, e.g., of the duodenum and stomach (particularly ampullary adenocarcinoma). Other signs that may point to FAP are pigmented lesions of the retina ("CHRPE—congenital hypertrophy of the retinal pigment epithelium"), jaw cysts, sebaceous cysts, and osteomata (benign bone tumors). The combination of polyposis, osteomas, fibromas and sebaceous cysts is termed "Gardner's syndrome" (with or without abnormal scarring).

Attenuated familial adenomatous polyposis is a form of familial adenomatous polyposis, a cancer syndrome. It is a pre-malignant disease that can develop into colorectal cancer. A patient will have fewer than a hundred polyps located typically in right side of the colon. Cancer might develop as early as the age of five, though typically presents later than classical FAP.

Gardner syndrome, also known as Gardner's syndrome or familial colorectal polyposis, is an autosomal dominant form of polyposis characterized by the presence of multiple polyps in the colon together with tumors outside the colon. The extracolonic tumors may include osteomas of the skull, thyroid cancer, epidermoid cysts, fibromas, as well as the occurrence of desmoid tumors in approximately 15% of affected individuals.

Desmoid tumors are fibrous tumors which usually occur in the tissue covering the intestines and may be provoked by surgery to remove the colon. The countless polyps in the colon predispose to the development of colon cancer; if the colon is not removed, the chance of colon cancer is considered to be very significant. Polyps may also grow in the stomach, duodenum, spleen, kidneys, liver, mesentery and small bowel. In a small number of cases, polyps have also appeared in the cerebellum. Cancers related to Gardner syndrome commonly appear in the thyroid, liver and kidneys. The number of polyps increases with age, and hundreds to thousands of polyps can develop in the colon.

The syndrome was first described in 1951. There is no cure at this time, and in its more advanced forms, it is considered a terminal diagnosis with a life expectancy of 35–45 years; treatments are surgery and palliative care, although some chemotherapy has been tried with limited success.

Pilomatricoma, also known as a calcifying epithelioma of Malherbe, Malherbe calcifying epithelioma, and Pilomatrixoma, is a benign skin tumor derived from the hair matrix. These neoplasms are relatively uncommon and typically occur on the scalp, face, and upper extremities. Clinically, pilomatricomas present as a subcutaneous nodule or cyst with unremarkable overlying epidermis that can range in size from 0.5-3.0 cm, but the largest reported case was 24 cm.

Hereditary nonpolyposis colorectal cancer (HNPCC) or Lynch syndrome is an autosomal dominant genetic condition that has a high risk of colon cancer as well as other cancers including endometrial cancer (second most common), ovary, stomach, small intestine, hepatobiliary tract, upper urinary tract, brain, and skin. The increased risk for these cancers is due to inherited mutations that impair DNA mismatch repair. It is a type of cancer syndrome.

Familial adenomatous polyposis (FAP) is an autosomal dominant inherited condition in which numerous adenomatous polyps form mainly in the epithelium of the large intestine. While these polyps start out benign, malignant transformation into colon cancer occurs when they are left untreated. Three variants are known to exist, FAP and attenuated FAP (originally called hereditary flat adenoma syndrome) are caused by APC gene defects on chromosome 5 while autosomal recessive FAP (or MYH-associated polyposis) is caused by defects in the "MUTYH" gene on chromosome 1. Of the three, FAP itself is the most severe and most common; although for all three, the resulting colonic polyps and cancers are confined to the colon wall and removal can greatly reduce the spread of cancer.

The root cause of FAP is understood to be a genetic mutation—a flaw in the body's tumour suppressor genes that prevent development of tumours. The flaw allows numerous cells of the intestinal wall to develop into potentially cancerous polyps when they would usually reach the end of their life; inevitably one or more will eventually progress and give rise to cancer (7% risk by age 21, rising to 87% by age 45 and 93% by age 50). The flawed genes do not trigger cancer, but rather, they reduce the body's ability to protect against the risk of aged cells becoming cancerous. Even with the flawed gene, it may still take time before a cell actually does develop that is cancerous as a result, and the gene may in some cases still partially operate to control tumours, therefore cancer from FAP takes many years to develop and is almost always an adult-onset disease.

The second form of FAP, known as attenuated familial adenomatous polyposis has the APC gene functional but slightly impaired. It is therefore somewhat able to operate as usual. Attenuated FAP still presents a high 70% lifetime risk of cancer (as estimated), but typically presents with far fewer polyps (typically 30) rather than the hundreds or thousands usually found in FAP, and arises at an age when FAP is usually no longer considered likely—typically between 40 and 70 years old (average 55) rather than the more usual 30's upward. Because it has far fewer polyps, options for management may be different.

The third variant, autosomal recessive familial adenomatous polyposis or MYH-associated polyposis, is also milder and, as its name suggests, requires both parents to be 'carriers' to manifest the condition.

In some cases FAP can manifest higher in the colon than usual (for example, the ascending colon, or proximal to the splenic flexure, or in the gastric or duodenal tracts) where they show no symptoms until cancer is present and greatly advanced. APC mutations have been linked to certain other cancers such as thyroid cancer. As the mutation causing FAP is genetic, it can be inherited hereditarily from either parent, and passed to children. A genetic blood test of the APC gene exists that can determine whether it is deficient, and therefore can predict the possibility of FAP. Individuals at risk (due to family links or genetic testing) are usually offered routine monitoring of the intestinal tract every 1 – 5 years for life, from early adulthood, to detect the slow-forming polyps and act if found, before they can pose a threat. International polyposis registries exists that track known cases of FAP or APC gene defects, for research and clinical purposes. Mutation of APC also occurs commonly in incident cases of colorectal carcinoma, emphasizing its importance in this form of cancer.

Mismatch repair cancer syndrome (MMRCS) is a cancer syndrome associated with biallelic DNA mismatch repair mutations. It is also known as Turcot syndrome (after Jacques Turcot, who described the condition in 1959) and by several other names.

In MMRCS, neoplasia typically occurs in both the gut and the central nervous system (CNS). In the large intestine, familial adenomatous polyposis occurs; in the CNS, brain tumors.

Symptoms of polyps include nasal congestion, sinusitis, loss of smell, thick nasal discharge, facial pressure, nasal speech, and mouth breathing. Recurrent sinusitis can result from polyps. Long-term, nasal polyps can cause destruction of the nasal bones and widening of the nose.

As polyps grow larger, they eventually prolapse into the nasal cavity resulting in symptoms. The most prominent symptoms of nasal polyps result blockage of the nasal passage.

People with nasal polyps due to aspirin intolerance often have symptoms known as Samter's triad, which consists of asthma worse with aspirin, a skin rash caused by aspirin, and chronic nasal polyps.

Pseudopolyps are projecting masses of scar tissue that develop from granulation tissue during the healing phase in repeated cycle of ulceration (especially in inflammatory bowel disease). Inflammatory tissue without malignant potential, pseudopolyps may, according to Joffe (1977), represent either regenerating mucosal islands between areas of ulceration, edematous polypoid tags or granulation tissue covered by epithelium. There are reported cases when localized giant pseudopolyposis resulted in intestinal obstruction.

Residual mucosal islands between ulcerated and denuded areas of mucosa may have a polypoid appearance and are referred to as pseudopolyps. Polyposis syndromes, such as familial adenomatous polyposis, could give rise to a similar appearance on imaging, although the clinical presentation would differ from that of inflammatory pseudopolyposis.

Numerous, confluent ulcerations with bulging of the edematous residual mucosa determine a cobblestone appearance at endoscopy.

SSAs, generally, are asymptomatic. They are typically identified on a colonoscopy and excised for a definitive diagnosis and treatment.

Gardner syndrome consists of adenomatous polyps of the gastrointestinal tract, desmoid tumours, osteomas, epidermoid cysts, lipomas, dental abnormalities and periampullary carcinomas. The incidence of the syndrome is 1:14,025 with an equal sex distribution. It is determined by the autosomal dominant familial polyposis coli gene (APC) on chromosome

5.

Gardner syndrome can be identified based on oral findings, including multiple impacted and supernumerary teeth, multiple jaw osteomas which give a "cotton-wool" appearance to the jaws, as well as multiple odontomas, congenital

hypertrophy of the retinal pigment epithelium (CHRPE), in addition to multiple adenomatous polyps of the colon. Gardner syndrome is also associated with familial adenomatous polyposis and may manifest as aggressive fibromatosis (desmoid tumors) of the retroperitoneum.

Desmoid tumors arise most frequently from the aponeurosis of the rectus abdominal muscle of multiparous women. The extra-abdominal form is rare and desmoids of the breast may arise in the mammary gland or may occur as an extension of a lesion arising from the muscles of the chest wall. The incidence of mammary desmoid tumours is less than 0.2% of primary breast neoplasms.

In Gardner’s syndrome the incidence ranges from 4% to 17%. Desmoid tumours associated with Gardner’s syndrome have been shown to have an alteration of the β-catenin pathway and over express β-catenin.

Pilomatricomas have been observed in a variety of genetic disorders including Turner syndrome, myotonic dystrophy, Rubinstein-Taybi syndrome. Trisomy 9, and Gardner syndrome. It has been reported that the prevalence of pilomatricomas in Turner syndrome is 2.6%.

Hybrid cysts that are composed of epidermal inclusion cysts and pilomatricoma-like changes have been repeatedly observed in Gardner syndrome. This association has prognostic important since cutaneous findings in children with Gardner Syndrome generally precede colonic polyposis.

The Amsterdam clinical criteria identifies candidates for genetic testing, and genetic testing can make a diagnosis of Lynch syndrome. Genetic testing is commercially available and consists of a blood test.