Pure mucinous carcinoma of the breast: clinicopathologic characteristics and long-term outcome among Taiwanese women

BACKGROUND Pure mucinous carcinoma (MC) is found in about 3.5% of all newly diagnosed breast cancer patients in Taiwan. MC is a relatively rare malignancy of breast cancer, and its nature, behaviors, treatment pattern and long-term follow-up are not well understood. The study aimed to investigate the incidence rate, treatment patterns, and prognostic factors of MC of the breast and the clinical long-term outcomes compared with infiltrating ductal carcinoma not otherwise specified (IDC) in the middle and south Taiwanese women. METHODS Data from 93 patients with breast MC were retrospectively reviewed and the clinicopathologic characteristics and survival status were compared with those of 2,674 patients with IDC. RESULTS The expression of hormonal receptor was higher in MC than those in IDC (P <0.001). MC also demonstrated lower Her2/neu gene over-expression (P = 0.023), less axillary lymph node involvement (P <0.0001), lymphovascular invasion (P <0.0001) and higher 10-year overall survival rate (P = 0.042), when compared with those of IDC. CONCLUSION Our data confirm the less aggressive behavior of MC compared to IDC. MC showed favorable clinicopathologic characteristics in tumor grade, hormone receptor status and lymph node involvement in the middle and south Taiwanese women.