Although treatment is started with surgery in early stage tumors depending on the molecular subtype, neoadjuvant chemotherapy is the initial treatment in locally advanced tumors or if axillary lymph node involvement is present.

Axillary lymph node dissection (ALND) has been used for a very long time in the traditional approach to the treatment of breast cancer. The current approach in patients with early stage, clinically negative breast cancer of the axilla is sentinel lymph node biopsy (SLNB). SLNB is done to evaluate the axilla in both early stage tumors and suitable patients after NAC. According to ACOSOG Z1071, when at least 3 lymph nodes were removed using lymphoscintigraphy and blue dye for SLNB, the false-negative rate was found to be less than 10% in patients with proven axillary involvement, and SLNB was shown to be feasible after NAC. Targeted axillary dissection (TAD) is a procedure that includes SLND with removal of the lymph node identified and marked as containing metastatic disease before treatment. Multiple clinical studies have shown that TAD is a viable option to reduce false-negativeness in patients with breast cancer after NAC. In patients with axillary involvement, a metallic clip is placed in the suspected lymph node prior to neoadjuvant therapy and a radioactive iodine-125 seed is implanted into the target after completion of chemotherapy, and during TAD, the core node is removed using a radioactive probe. Today, the applicability of these procedures is difficult due to both the cost and the absence of nuclear medicine units in some hospitals. For this reason, alternative methods that can be applied more easily in the evaluation of the axilla after NAC are being investigated. SPOT ENDOSCOPIC MARKER is an FDA (American Food and Drug Administration) approved Carbon Black Tattoo paint that has been used for a long time to mark lesions in the gastrointestinal tract. Its shelf life is 20 months. In our project, in patients with lymph node involvement in the axilla who have had a metallic clip placed with biopsy before NAC, the lymph node will be marked with a Spot Endoscopic Marker simultaneously, and the permanence of the spot marker dye will be evaluated by excising the clip-marked and black-painted lymph node in addition to the methylen blue injected during the operation. The reliability of the use of Spot Endoscopic Marker, which is much cheaper instead of clips, for permanent axillary marking in TAD will be evaluated.

Breast cancer affects millions of women worldwide. According to the statistics, 2.3 million new cases of breast cancer were reported in 2020. Although treatment is started with surgery in early stage tumors depending on the molecular subtype, neoadjuvant chemotherapy is the initial treatment in locally advanced tumors or if axillary lymph node involvement is present. With NAC in locally advanced breast cancer, it is possible to both shrink the tumor and make patients who were initially inoperable suitable for surgery, and increase the feasibility of breast-conserving surgery.

Although axillary lymph node dissection (ALND) has been used for a very long time in the traditional approach to the treatment of breast cancer, the current approach in patients with early stage, clinically negative breast cancer of the axilla is sentinel lymph node biopsy (SLNB). SLNB is done to evaluate the axilla in both early stage tumors and suitable patients after NAC. According to ACOSOG Z1071, when at least 3 lymph nodes were removed using lymphoscintigraphy and blue dye for SLNB, the false-negative rate was found to be less than 10% in patients with proven axillary involvement, and SLNB was shown to be feasible after NAC. Targeted axillary dissection (TAD) is a procedure that includes SLND with removal of the lymph node identified and marked as containing metastatic disease before treatment. Multiple clinical studies have shown that TAD is a viable option to reduce false-negativeness in patients with breast cancer after NAC. In patients with axillary involvement, a metallic clip is placed in the suspected lymph node prior to neoadjuvant therapy and a radioactive iodine-125 seed is implanted into the target after completion of chemotherapy, and during TAD, the core node is removed using a radioactive probe. The procedure is performed with SLND using the dual-tracer technique. Today, the applicability of these procedures is difficult due to both the cost and the absence of nuclear medicine units in some hospitals. For this reason, alternative methods that can be applied more easily in the evaluation of the axilla after NAC are being investigated. SPOT ENDOSCOPIC MARKER is an FDA (American Food and Drug Administration) approved Carbon Black Tattoo paint that has been used for a long time to mark lesions in the gastrointestinal tract. Its shelf life is 20 months. In our project, in patients with lymph node involvement in the axilla who have had a metallic clip placed with biopsy before NAC, the lymph node will be marked with a Spot Endoscopic Marker simultaneously, and the permanence of the spot marker dye will be evaluated by excising the clip-marked and black-painted lymph node in addition to the methylen blue injected during the operation. The reliability of the use of Spot Endoscopic Marker, which is much cheaper instead of clips, for permanent axillary marking in TAD will be evaluated.

Inclusion Criteria:

• Patients with locally advanced breast cancer known to have metastases to the axillary lymph nodes at baseline and referred for neoadjuvant chemotherapy will be included in the study.

Exclusion Criteria:

• diagnosis by excisional biopsy
• previous axillary surgery
• failure to complete neoadjuvant therapy
• progression during therapy.