M Dydo, J Shutter. University of South Florida, Tampa, FL
Background: Mammaprint® is a 70 gene FDA approved gene expression profile used to stratify invasive breast cancer patients into recurrence risk categories using fresh tissue(Figure 1). This test also produces ER/PR and Her-2/Neu gene signatures. The purpose of this pilot study was to correlate the results of routine quantitative immunohistochemisty (IHC) of ER/PR and Her2/Neu protein expression to that of Mammaprint® gene expression profiling.
Design: Fresh tissue was sent for Mammaprint® analysis on 29 patients treated at the University of South Florida Breast Health Center with suspected or biopsy proven diagnosis of invasive breast cancer from 6/09 through 9/09. Fresh tissue samples were obtained by core biopsy or at the time of surgical excision. A gene expression profile for ER/PR and Her-2/Neu was included in the analysis where tumor volume was sufficient (> 30% tumor/connective tissue ratio). The remainder of the tissue was routinely processed for pathologic analysis and evaluation of ER/PR and Her-2/Neu status was performed by IHC. ER/PR was considered positive for ≥ 1% positive nuclear staining.
Results: ER/PR and Her2/Neu data were obtained for both Mammaprint® and IHC for 15 patients. Thirteen out of 15 (87%) cases were ER/PR concordant when comparing IHC to Mammaprint® results (Table 1). The two discordant cases were ER/PR positive by Mammaprint® and ER/PR negative by IHC. All cases were Her2/Neu concordant (Table 2).