Which of the following is true about Familial adenomatous polyposis (FAP)?
Correct Answer: It is less common than HNPCC
Description: Ans. B. it is less common than HNPCC. (Ref Harrisonys 18th/ Chapter 296.)HNPCC is the most common hereditary colorectal cancer syndrome.Hereditable (Autosomal Dominant) Gastrointestinal Polyposis SyndromesSyndromeDistribution of PolypsHistologic TypeMalignant PotentialAssociated LesionsFamilial adenomatous polyposisLarge intestineAdenomaCommonNoneGardner's syndromeLarge and small intestinesAdenomaCommonOsteomas, fibromas, lipomas, epidermoid cysts, ampullary cancers, congenital hypertrophy of retinal pigment epithelium (CHRPE)Turcot's syndromeLarge intestineAdenomaCommonBrain tumorsNonpolyposis syndrome (Lynch syndrome)Large intestine (often proximal)AdenomaCommonEndometrial and ovarian tumorsPeutz-Jeghers syndromeSmall and large intestines, stomachHamartomaRareMucocutaneous pigmentation; tumors of the ovary, breast, pancreas, endometriumJuvenile polyposisLarge and small intestines, stomachHamartoma, rarely progressing to adenomaRareVarious congenital abnormalitiesPolyposis Coli (familial polyposis of the colon)# a rare condition with thousands of adenomatous polyps throughout the large bowel.# It is transmitted as an autosomal dominant trait.# Polyposis coli is associated with a deletion in the long arm of chromosome 5 in both neoplastic (somatic mutation) and normal (germ-line mutation) cells.# The presence of soft tissue and bony tumors, congenital hypertrophy of the retinal pigment epithelium, mesenteric desmoid tumors, and ampullary cancers in addition to the colonic polyps characterizes a subset of polyposis coli known as Gardner's syndrome. The appearance of malignant tumors of the CNS accompanying polyposis coli defines Turcot's syndrome.# The colonic polyps in all these conditions are rarely present before puberty but are generally evident in affected individuals by age 25. If the polyposis is not treated surgically, colorectal cancer will develop in almost all patients before age 40.# Once the multiple polyps are detected, patients should undergo a total colectomy. Medical therapy with NSAIDs such as sulindac and cyclooxygenase-2 inhibitors such as celecoxib can decrease the number and size of polyps in patients with polyposis coli; however only temporary, and NSAIDs are not proven to reduce the risk of cancer. Colectomy remains the primary therapy/prevention.# Proctosigmoidoscopy is a sufficient screening procedure because polyps tend to be evenly distributed from cecum to anus, making more-invasive and expensive techniques such as colonoscopy or barium enema unnecessary. The detection of such a germ-line mutation can lead to a definitive diagnosis before the development of polyps.Hereditary Nonpolyposis Colon Cancer (Lynch syndromei# autosomal dominant trait.# It is characterized by the presence of three or more relatives with histologically documented colorectal cancer, one of whom is a first-degree relative of the other two;# In contrast to polyposis coli, HNPCC is associated with an unusually high frequency of cancer arising in the proximal large bowel.# Association of colorectal cancer with either ovarian or endometrial CA is especially strong.# HNPCC is associated with germ-line mutations of hMSH2 on chromosome 2 and hMLHl on3.# Testing tumor cells through molecular analysis of DNA or immunohistochemical staining of paraffin-fixed tissue for "microsatellite instability" (sequence changes reflecting defective mismatch repair) in patients younger than age 50 with colorectal cancer and a positive family history.
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