• To estimate the positive predictive value (PPV) of the GeneSearch™ BLN Assay as measured against histology that is as accurate as possible in assessing whether a SLN is truly positive. [ Time Frame: 1 week ] [ Designated as safety issue: No ]
• To gather data on size of metastases (micrometastases versus macrometastases) identified by histology to examine the assay performance for various levels of metastases. [ Time Frame: 1 week ] [ Designated as safety issue: No ]

This post-approval study is designed to determine the performance of the FDA-approved GeneSearch™ BLN Assay when compared to the site's standard of care permanent section histological evaluation, and when compared to more extensive histological evaluation when the assay is being used by clinicians to make surgical decisions on complete axillary dissections (ALND).

The primary objective of this clinical study is to gather data to estimate the positive predictive concordance (PPC) between the GeneSearch™ BLN Assay and histology as routinely practiced, i.e., routine H&E histology of sentinel lymph node(s) (SLN) and, when available, routine histology of non-sentinel axillary lymph nodes (ALN). This study will provide information on the assay that will augment the performance data gained in pre-market validation studies. In addition, with the assay being used for ALND decision-making, the metastatic status of the non-sentinel axillary nodes can be taken into account in the performance measures, i.e., if the patient's sentinel or non-sentinel nodes are histologically positive, the patient will be considered positive for the primary comparison to the assay results.

• Blumencranz P, Whitworth PW, Deck K, Rosenberg A, Reintgen D, Beitsch P, Chagpar A, Julian T, Saha S, Mamounas E, Giuliano A, Simmons R. Scientific Impact Recognition Award. Sentinel node staging for breast cancer: intraoperative molecular pathology overcomes conventional histologic sampling errors. Am J Surg. 2007 Oct;194(4):426-32.
• Julian TB, Blumencranz P, Deck K, Whitworth P, Berry DA, Berry SM, Rosenberg A, Chagpar AB, Reintgen D, Beitsch P, Simmons R, Saha S, Mamounas EP, Giuliano A. Novel intraoperative molecular test for sentinel lymph node metastases in patients with early-stage breast cancer. J Clin Oncol. 2008 Jul 10;26(20):3338-45.
• Veys I, Majjaj S, Salgado R, Noterman D, Schobbens JC, Manouach F, Bourgeois P, Nogaret JM, Larsimont D, Durbecq V. Evaluation of the histological size of the sentinel lymph node metastases using RT-PCR assay: a rapid tool to estimate the risk of non-sentinel lymph node invasion in patients with breast cancer. Breast Cancer Res Treat. 2009 Sep 25; [Epub ahead of print]

Inclusion Criteria:

• Pre-operatively established diagnosis of invasive carcinoma of the breast
• Scheduled for axillary sentinel lymph node dissection as per standard of care at the clinical site for newly diagnosed breast cancer patients
• Patients for whom the GeneSearch™ BLN Assay will be used intra-operatively to make a decision for an axillary lymph node dissection
• 18 years of age or older
• Female or male
• Willing and able to give informed consent to participate in the study

Exclusion Criteria:

• Previous diagnosis of lymphoma
• Subjects participating in other research studies that would interfere with their full participation in this study
• Patients and/or conditions with 'interfering substances' as listed in the IFU.
• Patients who have had any pre-operative treatment for breast cancer including neoadjuvant and/or hormonal intervention such as aromatase inhibitors or tamoxifen