Background: Invasive micropapillary carcinoma(IMPC) is a rare variant of invasive breast cancer that is associated with a high incidence of lymph node(LN) metastasis. But, the meaning of focal micropapillary component has not been fully elucidated.

Methods: We retrospectively reviewed 88 invasive breast carcinoma cases with IMPC and focal micropapillary component.

Results: Sixty-four cases had micropapillary component only in operative specimens, 18 cases had only in core-needle specimens, and 6 cases had in both. Sixteen were diagnosed as IMPC, and 72 cases had focal micropapillary component with other histological type of invasive breast carcinoma; 65 cases with invasive ductal carcinoma, 6 cases with mucinous carcinoma and one with metaplastic carcinoma. There was one male patient. Mean age was 56.5 years old. Median tumor size was 2.5 cm. Forty two (47.7%) cases were nuclear grade(NG)1, 16 (18.2%) were NG2 and 30 (34.1%) were NG3. Seventy eight cases (90%) were ERand/orPgR positive and 18.5% were HER2 positive. Six cases had distant metastasis at initial diagnosis. LN metastases were observed in 63.6% of all cases, and this high rate of LN metastasis could be seen even in small tumor group; 45.5% in cases with tumor equal or less than 2 cm. In the group of IMPC, 40.0% had LN metastasis, and 56.9% in cases with focal micropapillary component. There was no significant difference between IMPC and focal micropapillary component by univariate analysis(p = 0.055). Multivariate analysis of all cases showed that tumor size(>2cm)(p = 0.047), NG(1 vs 2&3, p = 0.017), and lymphatic invasion(p = 0.001) were significantly associated with LN metastasis. No significant difference between IMPC and focal micropapillary component was showed by multivariate analysis also (p = 0.60). Hormone receptor status or HER2 status were also not correlated(p = 0.92, p = 0.27 respectively). Among female patients without neoadjuvant chemotherapy, sentinel lymph node biopsy(SLNB) were underwent in 38 cases, and 16 cases (42.1%) had positive sentinel lymph node(SLN). Fourteen patients underwent additional axillary dissection and 7 cases (50%) had non-SLN metastases. Among patients with SLNB, 12 patients had micropapillary component in needle biopsy specimens, and 6 (50%) cases had positive SLN.

Conclusion: Our data showed very high rate of LN metastasis in patients with micropapillary component, and this tendency still exists in cases with only focal micropapillary pattern. High positivity of SLNB was observed in these groups, and our data suggests that the findings of micropapillary component in CNB specimen could be used as a predictor of SLN metastasis.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P1-01-20.