This prospective, multicenter, 1:1 randomized, controlled trial is designed to evaluate the safety and effectiveness of the Breast Cancer Locator (BCL) in subjects with non-palpable invasive breast cancer or ductal carcinoma in situ (DCIS). Subjects will be randomized to breast conserving surgery (BCS) utilizing either the BCL or wire localization (WL) to guide surgery.

The BCL System is intended to be used to guide a surgeon when performing partial mastectomy for breast cancer and to minimize positive margins. The purpose of this study is to provide evidence that the BCL is safe, effective, and non-inferior to the standard of care (WL) in the removal of non-palpable invasive breast cancer and DCIS.

Investigators in the intervention group will be provided with a three dimensional (3D) image of the cancer in the breast which allows them to visualize the closest distance from the tumor to the skin and the chest wall and quantifies those distances. Investigators will also use a BCL, which is a patient specific, plastic, bra-like form that is transiently placed on the breast prior to surgery and allows the Investigator to mark the projected edges of the tumor on the breast skin and to place bracketing wires inside the breast which define the center of the cancer and distances 1 cm from the tumor edges defined by pre-operative supine MRI.

Inclusion Criteria:

• Female gender
• Age > 18 years
• Histologic diagnosis of invasive breast cancer or DCIS
• The surgeon determines that pre-operative tumor localization is required because the tumor cannot be definitively detected by palpation
• The tumor is unifocal or multifocal with satellite lesions < or = 2 cm from primary tumor
• The tumor enhances on prone breast MRI imaging
• The tumor is ≥ 1 cm in diameter on prone breast MRI
• Subject and surgeon agree to perform BCS
• Subject voluntarily provides informed consent

Exclusion Criteria:

• Absolute contraindication to MRI, including presence of implanted electrical device (e.g., pacemaker or neurostimulator), aneurysm clip, or metallic foreign body in or near eyes
• Severe claustrophobia that precludes prone or supine MRI
• Contraindication to use of gadolinium-based intravenous contrast, including life- threatening allergy
• Compromised renal function including chronic, severe kidney disease (GFR < 30 ml/min/1.73m2), or acute kidney injury
• Pregnancy - In women of childbearing potential, a urine pregnancy test will be performed
• Subjects who have received or plan to receive neoadjuvant chemotherapy
• Sternal notch to nipple distance of > 32 cm as measured in a sitting or standing position
• Measurement of widest circumference around breasts and arms > 135 cm for sites using 60cm bore scanners, and measurement of widest circumference around breasts and arms >145 cm for sites using 70 cm bore scanners
• Subjects with known allergy to materials present in the device
• Use of localization with devices other than a localization wire, including intraoperative ultrasound guidance, radiofrequency emitting implants, magnetic seeds, radioactive seeds, and tissue inspection devices (MarginProbe)
• Subject would require > 2 localization wires, if randomized to standard of care
• Subjects with multicentric tumors (additional tumors > 2 cm from primary)
• Subject would require chest wall muscle nerve block as part of the operation

Pathologist will be blinded to the study assignment (BCL vs. WL)