Invasive Colloid Carcinoma and the role of Ki-67 and HER2 – Two case reports

Mucinous carcinoma (also termed colloid carcinoma) of the breast accounts for 1%-6% of all breast cancer and is considered to have a good relative prognosis. The most common mammographic appearance of pure mucinous carcinoma is a high-density mass with circumscribed margins and on sonographic examination an isoechoic round mass with circumscribed margins. We report 2 cases of invasive mucinous carcinoma, in which one patient showed an intermediate recurrence risk based on Ki-67 and human epidermal growth factor receptor 2 negativity, while the other showed a low Ki-67 recurrence risk and human epidermal growth factor receptor 2 positive. We also review the literature on Ki-67 and human epidermal growth factor receptor 2 and explore the roles of these molecular markers in mucinous carcinomas.