Comparative analysis of clinicopathologic characteristics and molecular subtypes of invasive papillary carcinoma of the breast and invasive ductal carcinoma: results from SEER database.

PURPOSE: To investigate the difference of clinicopathologic characteristics and prognosis between invasive papillary carcinoma (IPC) and invasive ductal carcinoma (IDC) in breast cancer patients, and to further confirm the influence of molecular subtype on prognosis of IPC.

METHODS: A total of 158,132 eligible patients from 2010 to 2015 were identified from the Surveillance, Epidemiology, and End Results (SEER) database, of which 348 patients were IPC and 157,784 patients were IDC. We assessed the clinicopathologic characteristics, molecular subtypes and prognostic value of IPC and compared them with those of IDC.

RESULTS: IPC was more frequently presented with older age at diagnosis, less proportion of married and white race, lower grade, smaller tumor size, higher rates of negative nodal status, more AJCC stage I disease and HR+/Her2- breast cancer, and was less likely to be treated with mastectomy, chemotherapy, and radiation therapy than IDC (p<0.05). IPC had a better 5-year breast cancer-specific survival (BCSS) and overall survival (OS) rates than IDC. After adjusting confounding and matching the confounding factors, IPC patients were still associated with better BCSS. Regarding patients with specific subtypes, patients with IPC had more HR+/Her2- subtypes. In addition, HR+/Her2--IPC patients had a better BCSS than HR+/Her2--IDC patients, but OS was similar between the two groups. However, BCSS and OS did not differ in the two groups after matching the confounding factors. Subgroup analysis indicated that molecular subtype may be the main confounding factor in IPC prognosis.

CONCLUSIONS: IPC showed more favorable behavior than IDC, but prognosis was not as favorable as people once thought. The determination of the appropriate therapeutic regimen for IPC still needs to be made according to risk factors such as histological grade, pathological stage and molecular subtype.