Internal Mammary Lymph Node Biopsy during Microsurgical Breast Reconstruction: A Prospective Study

Background Accurate assessment of regional lymph node basins is critical for oncological management of breast cancer. The internal mammary lymph node (IMLN) basin directly drains the medial pole of the breast, but biopsy is not commonly performed. While the axillary sentinel lymph node sample remains the standard of care, the majority of patients who have been found to have a positive IMLN biopsy have simultaneously had negative axillary sentinel lymph nodes. This study prospectively examines routine IMLN biopsy during microsurgical breast reconstruction. Methods An IRB-approved study of routine IMLN biopsies in 270 consecutive patients who underwent microsurgical breast reconstruction was performed from July 1, 2018, to June 1, 2021. Recorded data included unilateral or bilateral breast reconstruction, unilateral or bilateral IMLN sampling, patient demographics, disease stage, and pathologic findings of IMLN. Results The majority of patients, 240 of 270 patients (88.9%), had bilateral reconstruction. Overall, 5 out of 270 (1.9%) patients had positive IMLN; one of these patients had positive axillary sentinel lymph nodes. The IMLN biopsy results in two of the five patients affected the clinical course as they were upstaged and required chemoradiation. Conclusion Direct visualization of the internal mammary lymph nodes during dissection of the recipient vessels for microsurgical breast reconstruction allows for convenient sampling, with minimal donor site morbidity and enhances the therapeutic management of patients in whom nodal involvement is present. As such, the authors recommend IMLN sampling.