The purpose of this trial is to show adequate assay performance on clinical samples tested in real time at the clinical site.

This study will determine the sensitivity, specificity, negative predictive value, and positive predictive value of the GeneSearch™ BLN Assay in patient samples by comparing its performance to that of the current methods -- permanent section Hematoxylin and Eosin (H&E) staining with IHC. Additional marker testing using probes associated with nodal metastases may be used in the assay performance calculations. The observed performance measures will be compared to those obtained in the larger U.S. registration trial to show that there are no differences in the assay's performance.

Inclusion Criteria:

• Previous diagnosis of carcinoma of the breast
• Patient scheduled for sentinel lymph node dissection as per standard of care at the clinical site
• 18 years or older
• Female or male, and
• Able and willing to give consent to participate in the study

Exclusion Criteria:

• Patients taking part in other research studies that would interfere with their full participation in this study

Patients with a previous diagnosis of breast cancer scheduled for sentinel lymph node dissection.