[262] Myoepithelial Marker Expression in Breast Core Biopsy High Grade DCIS as a Predictor of Invasive Carcinoma in Subsequent Resection Specimens

G Luo, A Somoza, G Hill, Q Zhai, F Lucas. University of Cincinnati, Cincinnati; Greater Cincinnati Pathologists, Inc, Cincinnati

Background: High-grade ductal carcinoma in-situ (DCIS) is a major risk factor in the development of invasive ductal carcinoma. Immunohistochemical (IHC) demonstration of myoepithelial cells provides convincing evidence against an invasive lesion. We analyzed a set of myoepithelial markers in core biopsies with only high grade DCIS to determine the staining pattern and correlation with followup excision.
Design: Thirty five cases of high grade DCIS in core biopsies with follow up excision were selected for a period between 2004 to 2009. All core biopsies were reviewed by two authors and high grade DCIS was confirmed. Myoepithelial markers [p63, calponin, smooth muscle myosin heavy chain (SMMHC), smooth muscle actin (SMA)] were immunostained and evaluated. Stain intensity (1 = weak; 2 = intermediate and 3 = strong), % partial absence of myoepithelium, and % of myoepithelial attenuation were scored for p63, calponin, and SMMHS. For SMA, only stain intensity was graded. We arbitrary established a threshold of > 20% absence of myoepithelium to be significant for all groups.
Results: Of the 35 cases, 7 (20%), had follow up invasive ductal carcinoma (Group 1) and 28 (80%) showed residual DCIS without invasion or no residual DCIS (Group 2). In group I, calponin (83%), p63 (86%), SMMHS (67%), showed significant partial absence of these three markers. In group 2, calponin (33%), p63 (54%), and SMMHS (48%) showed significant partial absence of these markers. There is no difference for % of attenuation between group1 vs group 2 (calponin- 85% vs 89%; p63- 100% vs 100%; SMMHS- 90% vs 97%). Both groups show decrease stain intensity for all the myoepithelial markers (compared with normal internal control), however no significant difference of stain intensity was observed between group1 vs group 2 (calponin- 100% vs 86%; p63- 85% vs 89%; SMMHS- 86% vs 89%; SMA- 83% vs 79%).
Conclusions: Our results show decreased stain intensity and attenuation of all myoepithelial markers in high grade DCIS. Most of the cases showed different degrees of partial absence of p63, calponin, and SMMHS. The percentage of partial absence of myoepithelium appears increased in cases with follow up invasive ductal carcinoma (Group 1). The biologic significance of this absence remains to be determined. However, our observations suggest that it may be taken into consideration for prediction of invasive carcinoma on follow-up excision.
Category: Breast

Wednesday, March 24, 2010 9:30 AM

Poster Session V # 38, Wednesday Morning

 

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