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Familial Adenomatous Polyposis
Published in Savio George Barreto, Shailesh V. Shrikhande, Dilemmas in Abdominal Surgery, 2020
Paul Kolarsick, Steven D. Wexner
Attenuated familial adenomatous polyposis (AFAP) syndrome is a phenotypic variant in which less than one hundred synchronous adenomas are detected (Figure 24.2). Attenuated familial adenomatous polyposis is associated with a later onset of polyposis, frequently a right-sided polyp distribution, and a lower lifetime colorectal cancer risk (up to 70%). Average age of colorectal cancer diagnosis is also later, generally greater than 50 years of age. However, there are a number of other disorders that can yield a similar phenotype to AFAP, such as MYH-associated polyposis syndrome, Lynch syndrome, polymerase proofreading-associated polyposis, or simply multiple sporadic adenomas. The diagnosis of AFAP is made based on clinical findings including adenoma number (typically ranging from 20 to 100, with an average of 30 adenomatous polyps), family history, and results of genetic testing [3]. Upper gastrointestinal findings and the risk of duodenal cancer are similar to classic FAP.
Hereditary Colorectal Cancer
Published in Peter Sagar, Andrew G. Hill, Charles H. Knowles, Stefan Post, Willem A. Bemelman, Patricia L. Roberts, Susan Galandiuk, John R.T. Monson, Michael R.B. Keighley, Norman S. Williams, Keighley & Williams’ Surgery of the Anus, Rectum and Colon, 2019
Patients undergo colonoscopy for a variety of reasons, including screening, surveillance (follow-up of a neoplasm) and symptoms. Findings that suggest a hereditary syndrome include an advanced neoplasm in a young patient (age 40) and multiple polyps that may be synchronous (>10 adenomas, >5 juvenile polyps, >2 hamartomas) or metachronous (>20 adenomas) (Table 42.3). Grover et al. used data from genetic testing laboratory to show that patients with 10–19 adenomas in their colon had risks of attenuated familial adenomatous polyposis (AFAP) of 5% and MYH-associated polyposis (MAP) of 4%. With 20–100 adenomas, the risks of carrying a germline mutation of either APC or MYH approximately doubled.5 Ten or more synchronous adenomas or >20 cumulative adenomas are therefore valid indications for germline genetic testing. Similarly the presence of multiple hamartomas suggests that genetic testing is indicated.6 Multiple serrated polyps indicate Serrated Polyposis Syndrome (SPS), and because of the phenotypic overlap of syndromes, panel testing is indicated. 7
Genetics of Endocrine Tumours
Published in John C Watkinson, Raymond W Clarke, Louise Jayne Clark, Adam J Donne, R James A England, Hisham M Mehanna, Gerald William McGarry, Sean Carrie, Basic Sciences Endocrine Surgery Rhinology, 2018
Waseem Ahmed, Prata Upasna, Dae Kim
Mutations in the APC gene cause FAP and attenuated familial adenomatous polyposis (AFAP). FAP is inherited as autosomal dominant and is characterized by multiple adenomatous polyps in the colon and rectum with a natural history of progression to colorectal carcinoma in nearly 100% of cases, usually by the age of 40. People with FAP have up to a 2% lifetime risk of developing papillary thyroid cancer (PTC). Women with FAP appear to be at greater risk than men (80:1) and develop a particular histological variant of PTC (cribriform morular variant of PTC) that demonstrates more indolent behaviour than the sporadic type.90
Optimizing the timing of colorectal surgery in patients with familial adenomatous polyposis in clinical practice
Published in Scandinavian Journal of Gastroenterology, 2019
Hans F. A. Vasen, Zeinab Ghorbanoghli, Bastian de Ruijter, Ro-Anne Trinidad, Alexandra M. J. Langers, Koen C. M. J. Peeters, Bert A. Bonsing, James C. H. Hardwick
Familial adenomatous polyposis (FAP) is a dominantly inherited syndrome caused by a mutation in the APC gene and characterized by the development of hundreds of adenomas in the colon and certain extracolonic features [1]. Colorectal adenomas usually develop in the second decade of life and if patients are left untreated, nearly all will develop cancer between the ages of 30 and 40 years [2]. However, about 10–20% of cases show a mild polyposis phenotype, which is referred to as ‘attenuated familial adenomatous polyposis’ (AFAP) [3]. This subtype of FAP is associated with specific mutations located at the extreme ends of the APC gene and in exon 9 [4].