Prevalence of CDH1 germline mutations in subjects with early onset or familial lobular breast cancer, a multicenter collaboration
11042 Background: Invasive lobular breast carcinoma (LBC) is part of the hereditary diffuse gastric cancer (HDGC) syndrome, associated with germline mutations in the E-cadherin (CDH1) gene. CDH1 mutations can be identified in 80% of families ascertained by DGC. The risk of DGC in CDH1 mutation carriers is 67% in males, and 83% in females; the estimated risk of LBC in women is 39–50% to age 80. Management of HDGC includes prophylactic gastrectomy. In this study, we estimated the prevalence of germline CDH1mutations among women with LBC who were either diagnosed at young age or had family history of breast cancer (BC). Methods: Germline DNA was collected from 383 women with LBC or mixed, lobular/ductal, BC from breast cancer programs, familial cancer clinics, and population-based cohorts. Germline BRCA1or BRCA2mutations carriers were excluded. Eligible women had (1) LBC before age 45 or (2) LBC at any age with at least two 1st or 2nd degree relatives with BC of any type. Denaturing high pressure liquid chromatography was undertaken, followed by direct sequencing of exons displaying changes. Results: At the time of submission 310 of 383 samples have been fully sequenced. One previously characterized missense mutation and four novel non-synonymous variants (1.6%) were found. Three of these women had LBC before 45 years and no family history of BC; two had BC family history. No gastric cancers were reported in these families. Functional assays to assess the pathogenicity of the variants are in process. Conclusions: These results confirm that CDH1 is responsible for a small proportion of familial and early onset LBC. Given the difficulty of identifying CDH1 mutations from BC history alone and the importance of managing the gastric cancer risk in CDH1carriers, these findings should underscore the need to obtain an accurate abdominal cancer family history from women with LBC. No significant financial relationships to disclose.