e22188 Background: In daily oncology practice, triple-negative invasive breast cancer is defined by negative immunohistochemistry for ER, PR and HER-2. Patients with this phenotype experience poor prognosis due to limited treatment options and intrinsic tumor biology. In a population-based case-control study, the Carolina Breast Cancer Study (Carey et al, JCO, 2004: suppl; abstr 9510), the triple-negative phenotype in African-American women represented 33.9% of the tumors. We aimed to identify the incidence of triple-negative invasive breast cancer in a group of women living in a predominantly Hispanic population on the Texas- Mexico border. Methods: We collected retrospective data for all invasive breast cases diagnosed between January 2005 and December 2008 at our affiliated county hospital. Clinical and pathological features were summarized. ER, PR and HER-2 was performed by immunohistochemistry. Results: 309 patients with invasive breast cancer were identified. 23.9% (74 patients) of all breast cancer patients were triple-negative. 70 of the 74 subjects (94.6%) were Hispanic. There was equal distribution of patients over and under the age of 50. Histologically all cases were invasive ductal carcinoma. The vast majority had grade 3 tumors (82%) with a high Ki-67 proliferative index (97%). Lymphovascular invasion was present in 38 patients (51.4%). Distant metastases at diagnosis was found in 4 patients (5.4%). Conclusions: In our population-based study the proportion of triple-negative invasive breast cancer phenotype was not as high as in the Carolina Breast Cancer Study, but does reflect that a quarter of the patients with invasive breast cancer in this growing Hispanic population may carry this phenotype. The triple-negative phenotype was strongly associated with high tumor grade and proliferative index. No significant financial relationships to disclose.
Highly metastatic claudin-low mammary cancers can originate from luminal epithelial cells
