[279] Mammaglobin Based Assays for Detection of Minimal Residual Mammary Cancer Will Miss All Metaplastic and Medullary Carcinomas

C Reyes, A Mejias, C Gomez-Fernandez, M Nadji. University of Miami, Jackson Memorial Hospital and Sylvester Comprehensive Cancer Center, Miami, FL

Background: Mammaglobin (MGB) and Cytokeratin 19 (CK19) are the two most commonly utilized markers for the detection of minimal residual mammary carcinomas in sentinel lymph nodes or bone marrow. The purpose of this study was to explore the expression of these markers in common histologic subtypes of breast cancer.
Design: Core needle, or excisional biopsies from 1,123 untreated invasive mammary carcinomas were evaluated for the immunohistochemical expression of MGB and CK19. The staining result for MGB was semiquantitated as 1+ (less than 10% positive cells), 2+ (11% to 25% positive cells) and 3+ (more than 26% positive cells).
Results: Thirty-six carcinomas were classified as metaplastic (based on morphology; triple-negative, p63+), 38 as medullary (based on morphology; triple-negative; HLA-DR+), 44 lobular (morphology; E-Cadherin -) and 1,005 ductal carcinomas. All metaplastic and medullary carcinomas were negative for MGB. Thirty-three lobular (75%) and 492 ductal carcinomas (49%) showed positive reaction for MGB (1+= 43%; 2+= 23%; 3+= 34%). CK19 was expressed by 97% of all mammary carcinomas.
Conclusions: Mammaglobin-based assays for detection of minimal residual disease will fail to detect all medullary and metaplastic mammary cancers as well as more than 50% of ductal carcinomas.
Category: Breast

Wednesday, March 11, 2009 1:00 PM

Poster Session VI # 23, Wednesday Afternoon