Different prognosis by subtype in the early mucinous breast cancer: a SEER population-based analysis

Our study aims to investigate the clinicopathological characteristics and survival outcomes of mucinous breast cancer (MBC), and explore the effect of histology type on the breast cancer-specific survival (BCSS) by different subtypes.

we identified 7,083 patients who were diagnosed with MBC and 248,751 with infiltrating ductal carcinoma (IDC) by using the Surveillance, Epidemiology and End Results (SEER) database. The propensity score matching was used to match baseline characteristics among MBC and IDC, and multivariable cox proportional hazards models were used to analyze the relationship between histology type stratified by subtype and BCSS.

MBC patients were associated with a fewer nodal involvement, lower grade, earlier stage, more estrogen receptor (ER) or progesterone receptor (PR) positive, and more favorable prognosis compared to the overall IDC population. After 1:1 matching of MBC with IDC by other factors, we found that MBC patients presented better prognosis than the Matched IDC for BCSS. Analysis among ER+PR+ subgroup revealed that MBC patients was significantly better than that Matched IDC patients for BCSS (HR =0.78, 95% CI, 0.63-0.96). However, the survival analysis in the ER+PR- or ER-PR- subgroups suggested that no significant difference was seen between MBC patients and matched IDC patients for BCSS.

Our findings support that MBC seems to be an independent factor for the better prognosis for breast cancer patients with ER+PR+ breast cancer but not in those with ER+PR- or ER-PR- disease.