To reduce local recurrence, adjuvant locoregional radiotherapy is given routinely for post-mastectomy breast patients with 4 or more positive lymph nodes. Most institutions adopt a 3- or 4-field radiotherapy technique, in which the field and shielding placements are informed by bony anatomic landmarks viewed on digitally reconstructed radiographs.Here, we report on a 40-year-old woman who underwent a lumpectomy with axillary node dissection, followed by chemotherapy, completion mastectomy, and adjuvant locoregional radiotherapy (50 Gy in 25 fractions) for a multicentric pT1cN2aM0 invasive ductal carcinoma of the right breast. At 9 months after radiotherapy, she presented with a palpable brachial lymph node, a major draining node of the upper extremity, in the axilla, abutting the previous anterior supraclavicular and axillary radiation fields. This occurrence highlights the potential superolateral border of the level i axillary nodal chain and its relationship to the upper extremity lymphatics via the brachial ("sentry") node. Adapting the delineated nodal target volume in locoregional radiotherapy of the breast for disease with extensive nodal involvement or other high-risk pathologic indications may be warranted in certain situations. Careful imaging and an informed discussion with the patient is needed before deciding to treat the sentry node and including the acromial-clavicular joints, balanced with the potential increased risk of lymphedema.
Keywords: Breast cancer; lymph node; radiation field; regional radiotherapy; regional recurrence.