MedGen

APC-associated polyposis conditions include (classic or attenuated) familial adenomatous polyposis (FAP) and gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS). FAP is a colorectal cancer (CRC) predisposition syndrome that can manifest in either classic or attenuated form. Classic FAP is characterized by hundreds to thousands of adenomatous colonic polyps, beginning on average at age 16 years (range 7-36 years). For those with the classic form of FAP, 95% of individuals have polyps by age 35 years; CRC is inevitable without colectomy. The mean age of CRC diagnosis in untreated individuals is 39 years (range 34-43 years). The attenuated form is characterized by multiple colonic polyps (average of 30), more proximally located polyps, and a diagnosis of CRC at a later age than in classic FAP. For those with an attenuated form, there is a 70% lifetime risk of CRC and the mean age of diagnosis is 50-55 years. Extracolonic manifestations are variably present and include polyps of the stomach and duodenum, osteomas, dental abnormalities, congenital hypertrophy of the retinal pigment epithelium (CHRPE), benign cutaneous lesions, desmoid tumors, adrenal masses, and other associated cancers. GAPPS is characterized by proximal gastric polyposis, increased risk of gastric adenocarcinoma, and no duodenal or colonic involvement in most individuals reported. [from GeneReviews]

Lynch syndrome is characterized by an increased risk for colorectal cancer (CRC) and cancers of the endometrium, ovary, stomach, small bowel, urinary tract, biliary tract, brain (usually glioblastoma), skin (sebaceous adenomas, sebaceous carcinomas, and keratoacanthomas), pancreas, and prostate. Cancer risks and age of onset vary depending on the associated gene. Several other cancer types have been reported to occur in individuals with Lynch syndrome (e.g., breast, sarcomas, adrenocortical carcinoma). However, the data are not sufficient to demonstrate that the risk of developing these cancers is increased in individuals with Lynch syndrome. [from GeneReviews]

MUTYH polyposis (also referred to as MUTYH-associated polyposis, or MAP) is characterized by a greatly increased lifetime risk of colorectal cancer (CRC). Although typically associated with ten to a few hundred colonic adenomatous polyps, CRC develops in some individuals in the absence of polyposis. Serrated adenomas, hyperplastic/sessile serrated polyps, and mixed (hyperplastic and adenomatous) polyps can also occur. Duodenal adenomas are common, with an increased risk of duodenal cancer. The risk for malignancies of the ovary and bladder is also increased, and there is some evidence of an increased risk for breast and endometrial cancer. Additional reported features include thyroid nodules, benign adrenal lesions, jawbone cysts, and congenital hypertrophy of the retinal pigment epithelium. [from GeneReviews]

Lynch syndrome is characterized by an increased risk for colorectal cancer (CRC) and cancers of the endometrium, ovary, stomach, small bowel, urinary tract, biliary tract, brain (usually glioblastoma), skin (sebaceous adenomas, sebaceous carcinomas, and keratoacanthomas), pancreas, and prostate. Cancer risks and age of onset vary depending on the associated gene. Several other cancer types have been reported to occur in individuals with Lynch syndrome (e.g., breast, sarcomas, adrenocortical carcinoma). However, the data are not sufficient to demonstrate that the risk of developing these cancers is increased in individuals with Lynch syndrome. [from GeneReviews]

NTHL1 tumor syndrome is characterized by an increased lifetime risk for colorectal cancer (CRC), breast cancer, and colorectal polyposis. Colorectal polyps can be adenomatous, hyperplastic, and/or sessile serrated. Duodenal polyposis has also been reported. Additional cancers reported in individuals with NTHL1 tumor syndrome include endometrial cancer, cervical cancer, urothelial carcinoma of the bladder, meningiomas, unspecified brain tumors, basal cell carcinomas, head and neck squamous cell carcinomas, and hematologic malignancies. The cumulative lifetime risk of developing extracolonic cancer by age 60 years has been estimated at 35% to 78%. [from GeneReviews]

Hereditary mixed polyposis syndrome-2 (HMPS2) is characterized by colonic polyps of mixed hyperplastic, adenomatous, and occasional juvenile types. Polyposis eventually progresses to colorectal cancer (Cao et al., 2006). For a discussion of genetic heterogeneity of HMPS, see HMPS1 (601228). [from OMIM]

Mismatch repair cancer syndrome-4 (MMRCS4) is an autosomal recessive childhood cancer predisposition syndrome characterized by early-onset leukemia/lymphoma, brain tumors, colorectal/gastrointestinal cancers, and other rare malignancies, including rhabdomyosarcoma (summary by Li et al., 2015). Cafe-au-lait spots are usually present (De Vos et al., 2006). For a discussion of genetic heterogeneity of mismatch repair cancer syndrome, see MMRCS1 (276300). [from OMIM]

Oligodontia-cancer predisposition syndrome is a rare, genetic, odontologic disease characterized by congenital absence of six or more permanent teeth (excluding the third molars) in association with an increased risk for malignancies, ranging from gastrointestinal polyposis to early-onset colorectal cancer and/or breast cancer. Ectodermal dysplasia (manifesting with sparse hair and/or eyebrows) may also be associated. [from ORDO]

Familial adenomatous polyposis-4 is an autosomal recessive tumor predisposition syndrome characterized by the development of multiple colonic adenomas in adulthood, often with progression to colorectal cancer. Proliferative lesions in other tissues may also occur (summary by Adam et al., 2016). For a discussion of genetic heterogeneity of familial adenomatous polyposis, see FAP1 (175100). [from OMIM]

Tumor predisposition syndrome-2 (TPDS2) is an autosomal recessive cancer predisposition syndrome characterized by the onset of various types of tumors or malignancies in young adulthood. The most common clinical manifestations include acute myeloid leukemia (AML), myelodysplastic syndrome, colorectal adenomatous polyposis and carcinoma, and uveal melanoma, although other tumors and malignancies have been reported (summary by Palles et al., 2022). For a discussion of genetic heterogeneity of TPDS, see TPDS1 (614327). [from OMIM]

Presence of multiple adenomatous polyps in the colon. [from HPO]