Clinicopathological characteristics and prognostic marker of triple-negative breast cancer in older women.

Triple-negative breast cancer (TNBC) lacks an effective treatment target and is usually treated with chemotherapy. Treatment of older patients with TNBC, however, should be decided carefully because of the side effects of chemotherapy in this population. Some forms of TNBC are associated with a favorable prognosis and do not require chemotherapy. To optimize the treatment of older patients with TNBC, it is important to know the clinicopathological characteristics and a prognostic marker. In this study, classic clinicopathological factors, immunohistochemical characteristics (androgen receptor [AR], cytokeratin 5/6 [CK5/6], epidermal growth factor receptor), tumor-infiltrating lymphocytes (TILs), and the clinical outcome based on the status of each biomarker were compared among a consecutive series of female patients with TNBC aged ≥75 years (n = 75) and among those aged 55-64 years matched for the pathological stage (n = 47) who underwent surgery without neoadjuvant therapy. TNBC with special histology (particularly apocrine carcinoma, pleomorphic invasive lobular carcinoma, and metaplastic carcinoma) was more frequent in the older group than in the younger group (35/75, 57% versus 11/47, 23%, P = 0.010). The AR positivity rate was higher in older patients than in younger patients, whereas TILs and CK5/6 exhibited the opposite results. In multivariate analyses, AR positivity was an independent predictor of a favorable outcome in older patients (lower recurrence rate), whereas the high level of TILs was favorable in younger patients (lower recurrence and mortality rates). AR positivity or apocrine morphology was frequent and predicts a favorable clinical outcome in older patients with TNBC, suggesting the importance of AR examination in this population.