Breast Carcinoma with Basal Phenotype: Mammographic Findings

OBJECTIVE: Basal phenotype has been found to be an independent poor prognostic factor for breast cancer. The aim of this study was to assess the mammographic appearance of screening-detected breast carcinoma with the basal phenotype. MATERIALS AND METHODS: A series of 1,944 consecutively enrolled patients with operable invasive breast cancer underwent immunohistochemical analysis with cytokeratin 5/6 and cytokeratin 14 markers to identify tumors exhibiting basal phenotype characteristics. Among those patients, 356 women with breast cancer were common to a prospectively collected database of screening-detected cases of breast cancer. The predominant mammographic appearance and any associated features were reported by experienced image readers blinded to phenotype status. A chi-square test was used to assess difference between the mammographic appearances of a group of tumors with the basal phenotype and those of a group with the nonbasal phenotype. RESULTS: Forty-one (12%) of the screening-detected tumors had basal phenotypic expression, and these were compared with 309 (88%) nonbasal tumors. Basal-phenotype tumors were significantly more likely to manifest as an ill-defined mass (basal phenotype, 25 61% of 41 tumors; nonbasal phenotype, 75 24% of 309 tumors; p < 0.001) or with comedo calcification (basal phenotype, nine 22% of 41 tumors; nonbasal phenotype, 30 10% of 309 tumors; p = 0.019). Nonbasal-phenotype tumors were more likely to manifest as a spiculated mass (nonbasal phenotype, 150 49% of 309 tumors; basal phenotype, eight 20% of 41 tumors; p < 0.001). The low rate of spiculation in basal tumors was independent of histologic grade. CONCLUSION: Screening-detected breast tumors with a basal phenotype have a mammographic appearance different from that of nonbasal tumors. This finding may explain the good prognostic value of mammographic spiculation reported in previous studies.