Outcomes of Patients with Invasive Mucinous and Tubular Carcinomas of the Breast

Invasive tubular carcinoma (ITC) and invasive mucinous carcinoma (IMC) of the breast are rare histologic subtypes of breast cancer associated with favorable prognoses. The aim of our study was to investigate the outcomes for these rare subtypes using the National Cancer Database. Female patients diagnosed with ITC or IMC between 2005 and 2014 were analyzed. The primary outcome was overall survival (OS), and we analyzed its association with adjuvant therapy. 2735 patients with ITC and 5602 patients with IMC were identified. ITC presented in younger patients (57 vs. 67 years), had smaller tumors (size <1 >cm, 63.1% vs. 25.4%), earlier stage, and less node-positive disease (5% vs. 8.6%), compared with IMC. Older age, government insurance, lower income, treatment in a community cancer program, large tumor size, positive nodal status, and without endocrine therapy were associated with worse OS with either subtype on multivariate analysis. No OS benefit was found for node-positive ITC that received adjuvant chemotherapy compared with those who did not. (5-year OS of 96.0% vs. 91.3%, p = 0.17).OS was improved for IMC that received adjuvant chemotherapy (10-year OS: 82.5% vs. 60.1%, p = 0.008) and endocrine therapy (10-year OS: 86.6% vs. 81.2%, p < 0.001). We concluded that ITC has favorable clinicopathological characteristics and prognosis, even with node-positive disease. ITC and IMC may need to be evaluated independently when administering adjuvant treatment plans.