Background: : Basal-like breast cancers are a subgroup of breast cancers defined by the absence of staining for estrogen-receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER-2/neu) and by positive staining for the cytokeratins (CKs) expressed in the myoepithelial cells of the ducts and lobules (CK5/CK6, CK14) and for epidermal growth factor receptor (EGFR). This class of tumors has an unusually aggressive course, and it is not clear whether conventional prognostic factors for breast cancers also predict outcome for patients who have the basal phenotype.
Methods: : A panel of 962 breast cancers was stained for 5 markers (ER, PR, HER-2/neu, CK5/CK6, and EGFR). The patients were followed for clinical outcomes for up to 15 years from diagnosis, and the rates of distant disease recurrence and death were compared by tumor size (< or =2 cm or >2 cm) and by lymph node status within the subgroups of women with basal and nonbasal cancers.
Results: : Of the 962 women with breast cancer, 116 cancers were basal (12%), 845 were nonbasal (88%), and 1 could not be classified as either basal or nonbasal and was excluded. In total, 426 tumors measured < or =2 cm (45%), and 530 tumors measured >2 cm (55%). Among women with nonbasal cancers, large tumor size was an adverse prognostic factor. Among women with basal cancers, a transient adverse effect of size on disease recurrence was observed; however, after 10 years, mortality rates were equal for women with small tumors and women with large tumors.
Conclusions: : Among women with basal breast cancers, the long-term prognosis was similar for women with large tumors and women with small tumors. However, women with large basal tumors appeared to develop recurrent disease sooner. Cancer 2009. (c) 2009 American Cancer Society.