[123] Utility of Prostate-Specific Membrane Antigen (PSMA) Expression by Vascular Endothelial Cells in the Differential Diagnosis of Papillary Lesions of the Breast

Timothy M D'Alfonso, Brian D Robinson. Weill Cornell Medical College, New York, NY

Background: The classification of papillary lesions of the breast can be challenging, even with the use of myoepithelial markers, as some papillary carcinomas may show patchy positivity for myoepithelial cells while papillomas may focally lack staining. A definitive diagnosis of papillary carcinoma in needle core biopsy (NCB) can allow for preoperative planning of a sentinel lymph node biopsy and wider surgical margins, thus potentially sparing patients a second surgical procedure. Neovascular endothelium in a variety of malignancies has been documented to express PSMA protein by immunohistochemistry (IHC). In this study, we set out to determine whether neovasculature expression of PSMA may be useful in the classification of papillary lesions of the breast, with particular focus on atypical papillary lesions in NCB samples.
Design: 50 papillary lesions of the breast consisting of 17 papillomas, 17 papillary carcinomas, and 16 tumors classified as atypical papillary lesions were identified. Cases included 20 NCB, 26 excisional biopsies, and 4 mastectomies. IHC staining with PSMA was performed on representative formalin-fixed paraffin-embedded tissue sections of each case. Lesional vasculature was examined for the extent and intensity of PSMA staining. Papillary lesions with ≥ 5% of vessels staining or with 2-3+ intensity were considered positive for PSMA expression.
Results: Positive PSMA staining was seen in 5 of 19 (26%) papillomas, 5 of 10 (50%) atypical papillary lesions, and 14 of 21 (67%) papillary carcinomas (p=0.006). 12 cases were classified as atypical on NCB. Upon excision, 2 of these cases were classified as papilloma, 6 remained atypical, and 4 were diagnosed as papillary carcinoma. Neovasculature in 0 of 2 papillomas, 3 of 6 atypical papillary lesions, and 4 of 4 papillary carcinomas stained positive with PSMA on the NCB specimens. If atypical and malignant cases are grouped together, 0 of 2 benign cases stained with PSMA, whereas 7 of 10 atypical/malignant cases stained positive (specificity = 100%, sensitivity = 70%).
Conclusions: PSMA expression in neovasculature of papillary breast tumors is more frequently seen in atypical and malignant lesions compared to papillomas. Our findings suggest that PSMA may be a useful adjunct in classifying papillary breast lesions, particularly in those that are atypical on NCB. Investigation of PSMA expression in a larger series of such cases is ongoing.
Category: Breast

Wednesday, March 21, 2012 1:00 PM

Poster Session VI # 24, Wednesday Afternoon


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