We report on the case of a 41-year-old man with a recently diagnosed amelanotic ulcerated melanoma, with a Breslow thickness of 3.5mm and Clark level IV. He had a pre-existing mass in the axilla, which had grown in parallel to the developing tumor. A large regional lymph node was clinically suspected. Ultrasound (US) examination of the axilla showed a large benign lipoma but also a very atypical peripheral perfusion. At the same time, a sentinel node showed a peripheral perfusion on US. Fine-needle aspiration cytology was performed of the different lesions and showed a melanoma metastasis in the sentinel node. There after, a lymph node dissection was performed. The lipoma was seen in histopathology and even the peripheral perfusion was confirmed. US and US-guided fine-needle aspiration cytology can be easily applied in the diagnosis of lymph node metastases in melanoma patients and can help determine a benign or a malignant involvement.