This monocentric early feasibility first in human study is intended to evaluate safety and performance of intraoperative detection of light signals during electrosurgical breast cancer resection.

In consequence the data should also be taken to adapt technical features according to the findings. The study results will be utilized to design and to calculate the sample size for future pivotal studies after finalizing this study and to adapt the technical features of the system and/ or device. In the future pivotal study, the effectiveness of method and the reduction in R1 resection rate will be assessed with the final goal to provide continuous or real-time information about the tissue type that is currently cut.

The primary endpoint for this first in human feasibility study is the percentage of patients with no serious adverse event related to the investigational device.

After signing the informed consent the doctor and research team will determine if the participant meets all requirements for this study. During the second visit (V2) they will receive the treatment procedure with the investigational medical device (IMD). The follow up visit (V3) will be performed up to 7 days after the treatment procedure at the day of discharge from the hospital.

Inclusion Criteria:

1. Female patient with primary invasive breast cancer (NST or NST with DCIS component, including endocrine pretreatment according to standard of care therapy at the study site)
2. Solid tumor size ≥ 15 mm at screening, on sonography imaging
3. Breast conserving surgery
4. ≥ 18 years of age
5. Ability to provide written informed consent

Exclusion Criteria:

1. Neoadjuvant chemotherapy
2. Bilateral breast conserving surgery
3. Invasive lobular carcinoma, DCIS, LCIS
4. Suspicion of extensive DCIS component of NST tumor
5. Diagnosis of recurrent breast cancer
6. Previous radiotherapy
7. Patient is pregnant or lactating
8. Patient is wearing active implant (cardiac pacemaker, internal defibrillator, other active implant), passive implants (hip arthroplasties, tooth implants etc.) are allowed at the discretion of the principal investigator
9. According to physicians' assessment, patient is not able to follow study protocol (e.g., due to cognitive disease) or is not able to understand the nature, objectives, benefits, implications, risks and inconveniences of the clinical investigation