Prognostic markers for invasive micropapillary carcinoma of the breast: a population-based analysis.

BACKGROUND: Invasive micropapillary carcinoma (IMPC) is a rare and distinct variant of breast carcinoma with a high propensity for regional lymph node involvement. Because of its lymphotropic nature, IMPC is considered to have an unfavorable prognosis when compared with invasive ductal carcinoma (IDC).

PATIENTS AND METHODS: This study of 624 patients diagnosed with breast IMPC (2001-2008) listed in the National Cancer Institute's Surveillance, Epidemiology, and End Results (NCI SEER) database was performed to evaluate prognostic factors for disease-specific survival (DSS) and overall survival (OS).

RESULTS: The 5-year DSS and OS for patients with IMPC were 91.9% and 83.8%, respectively. Of those with known estrogen receptor (ER) status, 84.8% were ER-positive (ER(+)), which was associated with better DSS (hazard ratio [HR], 0.27; P < .0002) and OS (HR 0.45; P < .006). At presentation, 52.9% of the patients with lymph node examinations had nodal involvement and 4.1% had distant metastases. Patients with 4 or more positive lymph nodes had worse DSS (HR 6.43; P = .0013) and OS (HR 3.47; P = .00067) than did patients with node-negative disease, but those with 1 to 3 positive lymph nodes had DSS and OS similar to those of patients with node-negative disease.

CONCLUSION: Although IMPC has a high propensity for lymph node metastasis, it has a DSS and overall prognosis comparable to those of IDC. Patients with ER-negative (ER-) disease or those with 4 or more positive lymph nodes have the worst prognosis. This is the largest study of IMPC to date, and these findings will help address some of the inconsistencies regarding this rare histologic variant of breast cancer.