Abstract
Background: BRCA1 and BRCA2 are high-penetrance inherited genes; different founder mutations have been reported in various areas and races. By using trial registration data from the Japanese hereditary breast and ovarian cancer syndrome (HBOC) consortium, we aimed to explore the clinicopathological characteristics of breast cancer patients with the Japanese founder mutation BRCA1 L63X. Results: We found 88 BRCA1 carriers, 76 BRCA2 carriers, and one carrier of both BRCA1 and BRCA2. Of 46 independent BRCA1 mutations, the BRCA1 L63X mutation was detected in 26 patients. We observed a significant difference in the proportion of triple-negative breast cancer phenotype among 88.9%, 72.5%, and 26.8% of BRCA1 L63X mutation, BRCA1 mutation, and BRCA2 mutation carriers, respectively (p < .001). Additionally, significant differences were also observed in nuclear grade in the resultant breast cancer between the groups (p < .001). Conclusions: A high proportion of Japanese HBOC patients showed the BRCA1 L63X mutation, and the clinical characteristics of breast cancer in patients with this mutation might differ from those in patients with other BRCA1 or BRCA2 mutations, in terms of the subtype and nuclear grade of the resultant cancer. Methods: From 827 patients in the Japanese HBOC consortium through August 2015, patients with BRCA1/2 mutations were included in this study. We compared the clinicopathological features among patients with BRCA1 L63X mutation, other BRCA1 mutations, and BRCA2 mutations using Chi-square test.