2.3. Histopathology and BRCA Mutation Evaluation

After the operation, hematoxylin and eosin-stained slides of sections of gross residual tumor and LN(s) were assessed for a total of 273 patients by an experienced pathologist. The following molecular subtypes were classified according to ER, PR, HER2, and Ki-67 receptor status: luminal A (ER+ and/or PR+, HER2−, and negative Ki-67), luminal B (ER+ and/or PR+ and HER2+) or (ER+ and/or PR+ and HER2–, and positive Ki-67)), HER2-enriched (ER−, PR−, and HER2+), and triple-negative (ER−, PR−, and HER2−) [17].

BRCA mutation analysis was conducted mainly at the Department of Laboratory Medicine and Genetics at Samsung Medical Center with the cooperation of three other DNA testing laboratories, all of which are certified annually by the Korean Institute of Genetic Testing Evaluation. Genomic DNA was extracted and purified from peripheral blood leukocytes. The whole exons and the flanking intrinsic sequences of the BRCA1 gene or BRCA2 gene were amplified by polymerase chain reaction. The amplified products were directly sequenced, and the sequences were then compared with reference sequences using Sequencher software (Gene Codes Co., Ann Arbor, MI, USA). The nomenclature for BIC (Breast Cancer Information Core) traditional mutations was used, based on {"type":"entrez-nucleotide","attrs":{"text":"U14680","term_id":"555931","term_text":"U14680"}}U14680 (BRCA1) and {"type":"entrez-nucleotide","attrs":{"text":"U43746","term_id":"1161383","term_text":"U43746"}}U43746 (BRCA2). In addition, all mutations were described according to HUGO-approved systematic nomenclature (nomenclature for the description of sequence variations, Human Genome Variation Society. http://www.hgvs.org/mutnomen/). HUGO-approved mutation nomenclature of BRCA1 (GenBank accession no. {"type":"entrez-protein","attrs":{"text":"NP_009225.1","term_id":"6552299","term_text":"NP_009225.1"}}NP_009225.1) and BRCA2 (GenBank accession no. {"type":"entrez-protein","attrs":{"text":"NP_000050.2","term_id":"119395734","term_text":"NP_000050.2"}}NP_000050.2) defined the A of the ATG translation initiation codon as nucleotide +1. Splicing-defect mutations in intronic region were described at the genomic DNA level using GenBank genomic reference sequence {"type":"entrez-nucleotide","attrs":{"text":"NC_000017.10","term_id":"224589808","term_text":"NC_000017.10"}}NC_000017.10 (BRCA1) and {"type":"entrez-nucleotide","attrs":{"text":"NC_000013.10","term_id":"224589804","term_text":"NC_000013.10"}}NC_000013.10 (BRCA2). In addition, variants of unknown significance were excluded. Genetic testing of high-risk breast cancer patients was approved by the IRB of Samsung Medical Center (2010-09-006-001).