Screening for basal marker expression is necessary for decision of therapeutic strategy for triple-negative breast cancer

Background: Triple-negative breast cancer (estrogen receptor-negative, progesterone receptor-negative and Her2-negative) can be classified into two subtypes: basal and non-basal phenotype. Among these subtypes the basal phenotype is associated with poor outcome. Ordinarily, clinicopathological testing involves only screening for ER, PgR and Her2, and. for this reason the therapeutic approach that is decided for triple-negative disease is usually the same regardless of the subtype. Methods: Immunohistochemical staining was performed for the CK5/6, CK14, and CK17 basal markers in 66 triple-negative patients for the purpose of classifying as basal or non-basal phenotype, and the clinicopathology was investigated. Results: Forty (60.1%) were the basal phenotype. Compared with the non-basal phenotype, the basal phenotype lesions were significantly larger in diameter, higher incidences of EGFR-positive and a high nuclear grade. In the node-negative group the basal phenotype clearly showed those same clinicopathological differences and a higher incidence of distal recurrence compared with the non-basal phenotype. Conclusions: Although there was the small number of the patients, this study results show that it is important to perform basal marker immunohistochemical staining and classify lesions as the basal or the non-basal phenotype, since this will aid in deciding the therapeutic strategy for triple-negative breast cancer.