A 30-year-old female patient presented with a swelling of a cervical left lymph node measuring 1x3 cm, which had been presenting for three weeks. Lymph node excision revealed a metastasis of a malignant melanoma, but the primary tumor was not found. The guidelines recommend neck dissection and adjuvant systemic or immunotherapy. The patient opted for immunotherapy with pembrolizumab and was tumor-free one year later.