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Gastric cancer is comprised of two major types1: (1) intestinal, which is often associated with environmental factors such as diet, cigarette smoking, and Helicobacter pylori2; and (2) diffuse gastric cancer (DGC) which, although less common than the intestinal type, is more likely to be due to host factor effects.3 4 Hereditary diffuse gastric cancer (HDGC), which is featured in this editorial, was first described in 1964 in three Maori families from New Zealand.5 A descendant in one of the families died at age 14 years and more than 25 of his relatives also died of DGC. The pedigrees in these families were compatible with an autosomal dominant mode of genetic transmission for HDGC, which was subsequently attributed to mutations of the E-cadherin (CDH1), epithelial-cadherin (OMIM 19, 2009) gene, identified by Guilford et al6 in members of these Maori families.
Fitzgerald et al's article published in this issue6a discusses the veritable exponential increase of phenotypic and genotypic knowledge, consonant with HDGC's heterogeneity.5 It is now estimated that approximately 40% of HDGC families may harbour the CDH1 mutation.7 The mutation's penetrance is approximately 70%.8 9 Upper endoscopy shows the stomach mucosal surface to be “normal” while its diffuse signet ring cell pathology is submucosal, thereby making upper endoscopy an ineffective screening procedure. In addition to gastric cancer, approximately 40% of women with this CDH1 mutation will develop lobular carcinoma of the breast.3
Given these facts, it is clear that physicians and genetic counsellors must be highly knowledgeable about HDGC so that they can effectively provide accurate and compassionate genetic counselling, mandatory before collecting the patient's DNA for CDH1 mutation testing.10 11 The high risk family member needs to understand why he/she must give serious thought to the option …
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