Hereditary non-polyposis colorectal cancer (HNPCC), also known as Lynch syndrome, is an inherited condition which predisposes to a host of malignancies, including colorectal carcinoma. It is considered the most frequent form of hereditary colorectal cancer. Diagnosis requires evaluation using clinical criteria (see: Amsterdam criteria for HNPCC).
Typically HNPCC patients present in their forties and fifties with colorectal cancer 2, or with one of the associated malignancies. It is 5 times more common than familial adenomatous polyposis syndromes (FAP) 6.
HNPCC is due to mutations in DNA mismatch repair (MMR) genes 2, resulting most frequently in colorectal carcinoma (80% lifetime risk) as well as extracolonic malignancies, including 1-2:
- genitourinary tract malignancies
small bowel cancer: lifetime risk ~5% 4
- duodenum 45%
- jejunum 29%
- ileum 12%
- not specified 14%
- gastric cancer
- CNS tumours: most often glioblastoma
- Muir-Torre syndrome: HNPCC-variant with sebaceous tumours and keratoacanthocytomas
Radiographic features are related to the underlying conditions:
- colorectal carcinoma (CRC): more frequently right sided (70% proximal to the splenic flexure) 6. Despite the name, colorectal cancers arise from adenomatous polyps. Diffuse polyposis is characteristically absent.
- small bowel adenocarcinoma: most commonly duodenal
- endometrial carcinoma
- ovarian tumours
- urinary tract malignancies
Treatment and prognosis
The high risk of colorectal carcinoma warrants screening of the colon from 25-40 years of age 2, and may require colectomy. With close surveillance and resection of any adenomas which develop, the risk of CRC can be reduced by 60% 3.
Due to a high number of extracolonic tumours, various screening programs should also be instituted, such as transvaginal ultrasound screening of the uterus and ovaries and serum CA-125 2.
- 1. Kumar V, Abbas AK, Fausto N et-al. Robbins and Cotran pathologic basis of disease. W B Saunders Co. (2005) ISBN:0721601871. Read it at Google Books - Find it at Amazon
- 2. Hodgson SV, Eng C, Maher ER. A practical guide to human cancer genetics. Cambridge Univ Pr. (2007) ISBN:052168563X. Read it at Google Books - Find it at Amazon
- 3. Hauser SC, Pardi DS, Poterucha JJ. Mayo Clinic gastroenterology and hepatology board review. CRC Press. (2004) ISBN:0849320542. Read it at Google Books - Find it at Amazon
- 4. Schulmann K, Engel C, Propping P et-al. Small Bowel Cancer risk in Lynch Syndrome. Gut. 2008;doi:10.1136/gut.2007.140657 - Pubmed citation
- 5. Shinagare AB, Giardino AA, Jagannathan JP et-al. Hereditary cancer syndromes: a radiologist's perspective. AJR Am J Roentgenol. 2011;197 (6): W1001-7. doi:10.2214/AJR.11.6465 - Pubmed citation
- 6.Dahnert, Wolfgang, author. Radiology review manual I Wolfgang Dahnert, M.D., Department of Radiology, Aurora BayCare Medical Center, Green Bay, Wisconsin. - Seventh Edition.