Clinicopathological features and prognosis of mucinous breast carcinoma with a micropapillary structure

To conduct a comparative analysis of clinicopathological data between mucinous micropapillary breast carcinoma (MUMPC) and pure mucinous carcinoma (PMC) without a micropapillary structure to elucidate the distinctive clinicopathological characteristics of MUMPC and their impact on prognosis.

This retrospective analysis included 325 patients diagnosed with mammary mucinous carcinoma admitted to Tianjin Cancer Hospital between July 2014 and December 2019, including 197 patients with MUMPC and 128 patients with PMC without a micropapillary structure. Clinicopathological features were compared, and factors influencing the prognosis of MUMPC were analyzed. Survival analysis was conducted using the Kaplan-Meier method, and univariate and multivariate prognostic analyses for MUMPC were performed using the Cox proportional hazard regression model.

The median follow-up period was 76 months. In the MUMPC and PMC groups, the disease-free survival (DFS) rates at 3, 5, and 7 years were 95.4%, 90.4%, 89.8%, and 100%, 98.4%, and 96.9%, respectively, with a statistically significant difference between the two groups (p = 0.009). Tumor, node, and metastasis (TNM) stage, lymph node metastasis, and endocrine treatment were significant factors influencing the prognosis of the MUMPC group (p < 0.001). Multivariate analysis revealed that lymph node metastasis and endocrine therapy were independent prognostic factors in patients with MUMPC (p < 0.001). Compared with PMC, the MUMPC group exhibited a higher prevalence of HER2 (11.2% vs. 3.1%, p = 0.009) and Ki-67 overexpression (79.7% vs. 60.2%, p < 0.001).

The lymph node stage is the most crucial clinicopathological feature of MUMPC. Endocrine treatment strategy is an independent risk factor affecting the prognosis of MUMPC.