Abstract P6-01-03: Invasive Micropapillary Carcinoma (IMPC) of the Breast: An Uncommon but Aggressive Special Type of Breast Cancer

Abstract

Abstract IMPC is an uncommon type of invasive breast cancer. However, in comparison to invasive ductal carcinoma of no special type (IDC), it is reported to have a more aggressive behavior. Our objective was to compare and contrast IMPC with IDC in terms of clinicopathologic features and outcome. One hundred-thirty-one IMPC cases were compared to 1295 IDC and 189 invasive lobular carcinoma (ILC). Medical records and pathology slides were reviewed for traditional factors (tumor grade, lymphatic invasion [LVI], lymph node [LN] status, stage, receptor status, treatment) and specific tumor features (extent of retraction artifact [RA]). Clinicopathologic features between groups were compared and clinical outcome of IMPC was recorded. All patients were women with a median age of 57.6 yrs (range 22-93) for IMPC, 56.3 yrs (range 22-96) for IDC and 60.7 (range35-85) for ILC, respectively (P<0.0001). There were no differences noted for family history, race, or presentation (symptomatic vs. screening). Surgical treatment was partial mastectomy in 770 (47.7%) and mastectomy in 845 (52.3%). All patients had axillary lymph node biopsy. The median tumor size was 2.2 (range 0.3-15.2) cm for IMPC, 2.0 (range 0.05-11.0) cm for ILC and 1.7 (range 0.05-19.0) cm for IDC, respectively (P<0.). The extent of micropapillary features in IMPC ranged from 3% to 100% with a median value of 20%. LVI was more likely to be present in IMPC (67.9%) compared to IDC (28.3%) and ILC (6.9%) (P<0.0001). Axillary LN metastases were seen in 71.8% of IMPC compared to 44.1 % of IDC and 54.5% of ILC (P<0.0001). IMPC and ILC was significantly more frequently ER and PR positive (P<0.0001 each) compared to IDC, while ILC was significantly less frequently HER2 positive (2.8%) compared to IDC (17.9%) and IMPC (8.2%). The mean percent of tumors showing retraction artifact (RA) was 60.2% in IMPC compared to 25.4% in IDC and 3.8% in ILC (P<0.0001). During a median follow-up of 24.3 months 19 (14.5%) and 17 (13.0%) IMPC patients developed local and distant recurrence, respectively. IMPC is an uncommon special type of invasive breast cancer but it is more aggressive in reference to IDC and ILC based on larger tumor size and more frequent the presence of LVI and LN metastases. The presence of IMPC features in breast cancers, even if present focally, should alert the clinician for the high likelihood of lymphatic tumor spread and an adverse biologic behavior. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-01-03.