Introduction: Internal mammary lymph node (IMN) chain assessment for breast cancer is controversial; however, current oncologic data have shed new light on its importance. Metastatic involvement of the IMN chain has implications for staging, prognosis, treatment, and survival. Here, we analyzed our data gathered during sampling of the IMN and the oncologic treatment changes that resulted from our findings. Methods: A retrospective chart review was performed on 581 patients who underwent free-flap breast reconstruction performed by the senior author. All dissected IMNs were submitted for pathological examination. Patient demographics, oncologic data, and the results of IMN sampling were reviewed. Results: 581 patients undergoing 981 free flaps were identified. A total of 400 lymph node basins were harvested from 273 patients. Of these, nine had positive IMNs. Two of these nine patients had positive IMNs of the contralateral nonaffected breast. Five patients had positive axillary lymph nodes. Four patients had multifocal tumors, one of which was bilateral. Seven patients had an increase in cancer stage as a result of having positive IMNs. Six patients had a change in treatment: two patients required additional chemotherapy, one received adjuvant radiation therapy, and three necessitated both supplemental chemotherapy and radiation. Conclusions: Opportunistic biopsy of the IMN while dissecting the recipient vessels is simple and results in no added morbidity. We recommend that biopsy of the IMN chain be performed whenever internal mammary vessels are dissected for microsurgical anastomosis in breast cancer patients. Positive IMN involvement should encourage thorough oncological workup and treatment reevaluation. Level of Evidence IV: Case series.
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