Clinicopathological Characteristics and Survival Outcomes in Invasive Papillary Carcinoma of the Breast: A SEER Population-Based Study.

To investigate the clinicopathological characteristics and survival outcomes of invasive papillary carcinoma (IPC), we identified 233,171 female patients in the Surveillance, Epidemiology, and End Results (SEER) database who had IPC (n = 524) or infiltrating ductal carcinoma (IDC) (n = 232,647). Generally, IPCs occurred in older women (≥ 50 years old) and presented with smaller sizes, lower grades, higher rates of oestrogen receptor (ER) and progesterone receptor (PR) positivity, and reduced lymph node (LN) involvement and were less likely to be treated with mastectomy than patients with IDC. The five-year disease-specific survival (DSS) rates were significantly better in IPC than in IDC (97.5% vs. 93%, respectively; P < 0.001). In the multivariate analysis, patients with IPC showed a DSS that was similar to that of IDC (hazard ratio = 0.556, 95% confidence interval 0.289-1.070, P = 0.079). No significant difference was observed in DSS between matched IPC and IDC groups (P = 0.085). Differences in outcomes may be partially explained by differences in tumour grade, LN status, and ER and PR status between the 2 groups. Gaining an improved clinical and biological understanding of IPC might result in more tailored and effective therapies in breast cancer patients.