Clinical definition of hereditary non-polyposis colorectal cancer: a search for the impossible?

The phenotypic expression of three MSH2 mutations in large Newfoundland families with Lynch syndrome

To compare the phenotypic expression of three different MSH2 mutations causing Lynch syndrome, 290 family members at 50% risk of inheriting a mutation were studied. Two truncating mutations of the MSH2 gene have been identified in Newfoundland: an exon 8 deletion in five families (N=74 carriers) and an exon 4-16 deletion in one family (N=65 carriers). The third mutation was an intron 5 splice site mutation resulting in deletion of exon 5 in RNA and occurred in 12 families (N=151 carriers). Age to onset of first cancer, first colorectal cancer (CRC), first extracolonic cancers and death were compared. By age 60, 89% of family members with the intron 5 mutation, 81% with the exon 8 deletion, and 85% with the exon 4-16 deletion had developed cancer. For all three mutations males had a higher age-related risk of CRC and death compared to females. In the intron 5 splice site mutation carriers, the number of transitional cell cancers of the urinary tract was significantly lower and time to first ovarian cancer was significantly higher than in the carriers of the genomic deletions. The incidence of CRC in MSH2 mutation carriers, exposed to the same environment, is not modified by the specific mutation, although there is a suggestion that type of mutation may influence development of some extracolonic cancers.

[Implantation of a hospital registry of hereditary nonpolyposis colorectal cancer]

INTRODUCTION

Identification of patients with hereditary nonpolyposis colorectal cancer (HNPCC) can allow colorectal cancer (CRC) prevention through colonoscopy and polypectomies. The purpose of this study was to report the clinical characteristics of HNPCC families in our registry.

PATIENTS AND METHOD

HNPCC was identified using the Amsterdam criteria. Familial clustering of CRC and extracolonic cancers were investigated in families. Individuals at risk were offered annual colonoscopy, starting from the age of 25 years.

RESULTS

Twelve HNPCC families were identified. There were 46 cases of CRC in 38 patients. The mean age at diagnosis of CRC was 45.4 +/- 12.7 years (range 25-73 years). In patients with documented disease, right-sided tumors predominated. Eleven patients with extracolonic cancer were identified (six tumors located in the endometrium). Of 43 at-risk individuals, 29 accepted surveillance.

CONCLUSIONS

Our data confirm the importance of the family history in identifying HNPCC. This study confirms previously described characteristics in HNPCC, namely, early age at onset of CRC, right-sided predominance, multiple synchronous and metachronous neoplasms, and increased extracolonic cancers. This is the first study of clinical data in a Spanish HNPCC registry.

Hereditary non-polyposis colorectal cancer: The rise and fall of a confusing term

The term Hereditary Non-Polyposis Colorectal Cancer (HNPCC) is a poor descriptor of the syndrome described by Lynch. Over the last decade, the term has been applied to heterogeneous groups of families meeting limited clinical criteria, for example the Amsterdam criteria. It is now apparent that not all Amsterdam criteria-positive families have the Lynch syndrome. The term HNPCC has also been applied to clinical scenarios in which CRCs with DNA microsatellite instability are diagnosed but in which there is no vertical transmission of an altered DNA mismatch repair (MMR) gene. A term that has multiple, mutually incompatible meanings is highly problematic, particularly when it may influence the management of an individual family. The Lynch syndrome is best understood as a hereditary predisposition to malignancy that is explained by a germline mutation in a DNA MMR gene. The diagnosis does not depend in an absolute sense on any particular family pedigree structure or age of onset of malignancy. Families with a strong family history of colorectal cancer that do not have Lynch syndrome have been grouped as ‘Familial Colorectal Cancer Type-X’. The first step in characterizing these cancer families is to distinguish them from Lynch syndrome. The term HNPCC no longer serves any useful purpose and should be phased out.

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