Comparison of the characteristics of medullary breast carcinoma and invasive ductal carcinoma.

PURPOSE: Medullary breast carcinomas (MBC) have been known to represent a rare breast cancer subtype associated with a more favorable prognosis than invasive ductal carcinomas (IDC). The purpose of this study was to compare the clinicopathologic characteristics and outcomes of MBC with those of IDC.

METHODS: We retrospectively reviewed medical records of patients with invasive breast cancer who were managed surgically from August 1995 to June 2010.

RESULTS: Fifty-two patients were identified with MBC and 5,716 patients were identified with IDC. The clinicopathologic features, disease-free survival (DFS), and overall survival (OS) of patients with MBC were compared with those of patients with IDC. The MBC group presented at a younger age (p=0.005) and had a significant association with a higher histological grade (p=0.003) and nuclear grade (p<0.001) as well as negative estrogen receptor (p<0.001) and progesterone receptor (p<0.001) status. Lymphatic invasion was absent (p<0.001) and lymph node metastasis was rare (p<0.001). The DFS and OS did not differ significantly between the two groups (5-year DFS: 88.0% vs. 89.2%, p=0.920; 5-year OS: 93.4% vs. 94.4%, p=0.503). In multivariate analysis, the factors associated with DFS and OS were nuclear grade, histological grade, tumor size, lymph node metastasis, estrogen receptor status, progesterone receptor status, and human epidermal growth factor receptor 2 status, chemotherapy, and hormone therapy. However, DFS and OS were not significantly different between IDC and MBC according to histological type itself (DFS: hazard ratio 0.85, 95% confidence interval 0.12-6.05, p=0.866; OS: hazard ratio 1.49, 95% confidence interval 0.21-10.77, p=0.692).

CONCLUSION: Although MBC has specific clinicopathologic features, its prognosis does not differ from IDC and is determined by prognostic factors such as tumor size and lymph node metastasis. Therefore, patients with MBC also require the same intensive treatment provided for IDC.