Internal mammary node metastasis from primary cutaneous melanoma on the anterior chest

Direct lymphatic drainage from the skin of the anterior chest and breast to internal mammary lymph nodes does not normally occur.

Preoperative lymphoscintigraphy was performed in a 55-year-old man with a 3.7 mm-thick primary melanoma on his right anterior chest, who had undergone surgery and radiotherapy to successfully treat a localized lymphosarcoma in his right axilla 35 years earlier.

The sentinel node in the lower right internal mammary chain, in the 5th interspace, was removed at the same time as the primary melanoma site was widely excised, and micrometastatic melanoma was subsequently identified in it. Second-tier nodes in the 4th and 3rd right interspaces were therefore removed, and adjuvant radiotherapy was given to the entire internal mammary node chain.

This case demonstrates that major disturbance of normal lymphatic drainage pathways can result from previous surgery and/or radiotherapy. Also, the rarity of this drainage pattern indicates that attempts to identify sentinel nodes in breast cancer patients by injecting tracer into the skin overlying a tumour rather than into the breast tissue immediately adjacent to it are likely to be inaccurate in some patients, because cutaneous injection will not demonstrate the sentinel nodes in the internal mammary chain that are present in up to 40% of patients with a breast cancer.