Abstract
Invasive micropapillary carcinoma (IMPC) is a rare subtype of breast carcinoma. It is presumed to be more aggressive than invasive ductal carcinoma (IDC), though it is uncertain whether the prognoses of IMPC and IDC differ. In this retrospective study, we compared the clinicopathologic characteristics and survival between 170 female patients with IMPC (pure or mixed with IDC) and 728 with pure IDC. The IMPC patients had higher clinical stages and histologic grades, higher incidences of lymphovascular invasion and axillary lymph node extracapsular extension, and a higher degree of lymph node involvement than IDC patients. Moreover, IMPC was associated with increases in estrogen receptor (ER) and progesterone receptor (PR) positivity and HER-2 overexpression. Although locoregional recurrence-free survival (LRRFS) and recurrence-free survival (RFS) were poorer in IMPC patients than IDC patients, overall survival and distant metastasis survival did not differ between the two groups. Multivariate analysis revealed that IMPC was an independent prognostic factor for LRRFS in breast cancer, and IMPC patients had poorer clinicopathologic characteristics and poorer RFS and LRRFS than IDC patients. We therefore suggest that to improve treatment decisions, patients with breast carcinoma be tested for the presence of this specific subtype.
Highlights
Invasive micropapillary carcinoma (IMPC) of the breast, which was first defined by Siriaunkgul and Tavassoli, is characterized by micropapillae surrounded by empty stromal spaces [1, 2]
Among the 3,693 patients diagnosed with invasive breast cancer at our institution between January 2000 and April 2016 who were included in the database, we www.impactjournals.com/oncotarget identified 170 IMPC patients (4.6%) who received standard curative treatment without neoadjuvant chemotherapy
Previous studies reported that most patients had mixed IMPC [17, 18], which is consistent with our findings here that 154 (90.6%) patients had a 10% to 90% micropapillary growth pattern with other components
Summary
Invasive micropapillary carcinoma (IMPC) of the breast, which was first defined by Siriaunkgul and Tavassoli, is characterized by micropapillae surrounded by empty stromal spaces [1, 2]. The relatively low incidence of IMPC makes it difficult to directly compare its clinical outcomes and pathologic features to invasive ductal carcinoma (IDC). IMPC is more likely to have aggressive characteristics, such as high incidences of axillary lymph node (ALN) metastasis and local recurrence, compared to IDC [9, 10]. This would be expected to result in poorer outcomes for IMPC patients compared to IDC patients, reports have indicated that they have similar prognoses [6, 11]. Differences in the prognoses of IMPC and IDC require further investigation, and identifying the features that distinguish IMPC from IDC would help to improve disease management for IMPC patients
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