Contralateral axillary sentinel lymph node in chest wall melanoma: first documented case and narrative review of the literature.

This case report and literature review detail and contextualise the finding of a positive sentinel node in the contralateral axilla of a 69-year-old male with cutaneous malignant melanoma of the left chest wall. Excision biopsy confirmed nodular melanoma (Breslow thickness 6.6 mm; mitotic index 11; no ulceration or microsatellites; completely excised; pT4a). Preoperative lymphoscintigraphy identified the sentinel node in the right axilla. The patient underwent wide local excision with 2-cm margins and a sentinel lymph node biopsy, which showed no spread of disease. This was followed by six cycles of adjuvant pembrolizumab with surveillance scans remaining clear. Literature review identified 22 cases of anterior chest wall melanoma (n = 4) or breast carcinoma (n = 18) with contralateral drainage (12 case reports, two case series, and eight retrospective studies). Only one previous chest wall melanoma case with contralateral drainage was identified, but details were not reported. Thus, we present the first documented case of anterior chest wall melanoma with a contralateral sentinel node, and emphasise the importance of thorough evaluation of suspicious lesions for unexpected drainage patterns.