This is a study to evaluate the incidence of sampling bias during pathologic assessment of sentinel lymph nodes (SLN) when they are cut at a certain thickness (1 mm) and the tissue slices are completely analyzed by histopathology (at 200 µm sections). The sponsor and investigators would like to determine how often small cancer deposits are present in one slice but not the other. The data will provide an empirical estimate of the incidence of tissue sampling bias inherent in using different tissue sections for analysis. The data will also show how varying degrees of detail in evaluating the sentinel lymph nodes (SLN) with histopathology methods will impact the degree of agreement.

Inclusion Criteria:

• Male or female
• 18 years of age or older
• Diagnosed pre-surgically with T1 or T2 breast cancer and scheduled for surgery including sentinel lymph node dissection
• Subjects (or the subject's legal representative) who have read, understood (to the best of their ability) and signed the informed consent form.

Exclusion Criteria:

• Subjects diagnosed pre-surgically with large or locally advanced (T3 & T4) breast cancer
• Pregnant subjects, confirmed by interview with either subject or treating physician
• Subjects diagnosed with inflammatory breast cancer
• Subjects diagnosed with ductal carcinoma in situ (DCIS) when breast conservation is to be done
• Subjects with clinically suspicious, palpable axillary lymph nodes
• Subjects previously treated for or previously diagnosed with another type of invasive cancer. Subjects with skin cancer (basal cell and squamous cell carcinoma) may be included, except for subjects diagnosed with melanoma
• Subjects who have received pre-operative systemic therapy
• Subjects who are incapable of providing written informed consent
• Subjects who have been judged to be an inappropriate candidate by any medical care provider (e.g., surgeon, oncologist or pathologist).

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