The clinical relevance of micropapillary carcinoma of the breast : a case-control study

AIMS: To ascertain the prognostic relevance of micropapillary carcinoma, a specific type of breast tumour. METHODS AND RESULTS: We interrogated the clinical records of a series of 49 pure micropapillary carcinoma patients and 13 487 invasive ductal carcinoma patients, diagnosed and treated consecutively in our institution over a 9-year time-frame. Compared with invasive ductal carcinoma, patients with micropapillary carcinoma more frequently had moderately differentiated tumours (P = 0.02) with extensive peritumoral vascular invasion (P < 0.0001), associated with a significantly higher rate of axillary lymph node involvement (P < 0.0001). Survival data obtained by comparing 49 micropapillary carcinoma patients with a set of 98 invasive ductal carcinoma patients matched for age, tumour size and grade, peritumoral vascular invasion, immunohistochemically defined molecular subtype, number of positive lymph nodes and year of surgery showed that the micropapillary histotype did not add any independent information to the risk of locoregional (P = 0.48) or distant (P = 0.79) relapse, or overall survival (P = 0.60). CONCLUSIONS: Our data reinforce the notion that micropapillary carcinoma usually arises as a locally advanced disease, and provide evidence that micropapillary histology does not add any additional information on clinical outcome independent of clinicopathological characteristics such as lymph node status and immunohistochemically defined molecular subtype.