Outcomes of pleomorphic lobular carcinoma versus invasive lobular carcinoma

Purpose: Pleomorphic lobular carcinoma (PLC) is a rare histologic variant of invasive lobular carcinoma (ILC) that has been associated with worse clinical outcomes than classic ILC. Owing to its rarity, high-volume studies of its clinical characteristics and prognosis are lacking. The purpose of this study was to use a large, contemporary cancer database to investigate the clinical characteristics and survival outcomes for patients with PLC. Methods: The National Cancer Database (NCDB) was queried for women with cT1-4N1-3M0 breast cancer with either ILC or PLC histology having received definitive surgical therapy. Chi-squared analysis was performed to determine differences between the cohorts. Kaplan-Meier analysis evaluated overall survival (OS) between all patients and between patients when stratifying by age and subtype. Cox proportional hazards modeling determined variables associated with OS. Results: A total of 115,260 patients met the study criteria; of these, 114,859 (99.6%) had ILC, while 401 (0.4%) had PLC. A greater proportion of patients with PLC had T3-4 and node-positive disease, and were more likely to have ER- and HER2+ disease. PLC histology was associated with worse OS on both univariate and multivariate analysis (p < 0.001). PLC was associated with poorer OS in subgroups that were T3-4/N+ (but not T1-2N0) disease and ER+ (but not ER-) cancers, but not by HER2 status. Conclusions: Patients with PLC, who were more likely to have ER- and HER2+ disease, experienced worse OS than patients with ILC, which may be limited to patients with more advanced clinical stage and ER + disease. Further work is needed to determine the optimal treatment for this more aggressive form of breast cancer.