[178] P75/P63; a Novel Immunohistochemical Cocktail Which Is Diagnostically Superior to P63 for the Evaluation of Myoepithelial Cells in Challenging Breast Lesions

SJ Conlon, DE McCrae, SC Chak, SM Moran, FP O'Connell, TJ Browne. Cork University Hospital, Cork, Ireland

Background: Nerve growth Factor receptor (NGFR/p75NTR ) a cell surface receptor glycoprotein with cytoplasmic/membrane staining has been identified as an adjunct marker of myoepithelial cells (MECS). p63 is an established myoepithelial cell nuclear marker. MECS may be attenuated/discontinuous in challenging breast cases. The aim of the study was to combine the cytoplasmic/membranous pattern of p75 with the nuclear pattern of p63 in a novel immunohistochemical cocktail developed to improve detection of MECS in breast lesions.
Design: p63/p75 cocktail was developed and optimized. 100 breast excision specimens were retrieved from the files with institutional approval. H&E slides were reviewed to confirm the diagnosis. Sections were stained for p63, p75 and the p75 cocktail and scored independently by 2 pathologists. A scoring system evaluating distribution and intensity in basal, luminal and stromal cells was designed as follows - Distribution: 1=<5% cells positive, 2= 5-25%, 3=25-50%, 4=>50%; Intensity: 0=negative, 1=weak, 2=moderate, 3=strong. P63 was compared to both p75 alone and the p75 cocktail.
Results: Malignant lesions (n=71) included: 30 invasive carcinomas (12 ductal, 7 lobular, 1 mucinous, 6 tubular, 4 microinvasive); 40 in situ lesions (35 DCIS (14 involving sclerosing adenosis), 5 LCIS); 1 encysted papillary carcinoma. Benign lesions (n=29) included: 12 complex sclerosing lesions, 5 epithelial hyperplasia, 5 papillomas, 4 columnar cell lesions, 2 syringomatous adenomas, 1 lactational adenoma. 93% DCIS had moderate/strong intensity MECS with p75cocktail vs 74% with p63. 94% DCIS had score 3 or 4 MECS distribution with p75cocktail vs 76% with p63. 100% LCIS had moderate/strong intensity MECS with p75cocktail vs 80% with p63. 80% LCIS had score 3 or 4 MECS distribution with p75cocktail vs 40% with p63. 29/30 invasive carcinomas showed complete absence of staining with p63 or p75 cocktail. 1/30 cases showed focal weak staining for all stains. In benign lesions intensity was equal for p63 and p75 cocktail, however the distribution was consistently greater with p75 cocktail (100% score 4) vs p63 (45% score 4). Focal weak stromal staining for p75 and p75cocktail was present in a minority of cases but did not limit evaluation.
Conclusions: p63/P75 cocktail is a novel, highly sensitive and reliable marker for evaluation of MECS in benign, premalignant and malignant breast lesions. It's characteristic continuous strong staining pattern offers diagnostic advantages over p63 alone.
Category: Breast

Monday, March 22, 2010 1:00 PM

Poster Session II # 48, Monday Afternoon


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