Hereditary non-polyposis colorectal cancer
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.
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
- Turcot syndrome: HNPCC variant with CNS glioblastoma
Radiographic features are related to the underlying conditions:
- colorectal carcinoma (CRC): more frequently right sided; despite the name colorectal cancers arising from the adenomatous polyps, however, 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