Metastatic Renal Cell Carcinoma in a Supraclavicular Lymph Node with No Known Primary: A Case Report

Although metastasis is relatively frequent in cases of renal cell carcinoma (RCC), metastasis in the cervical or supraclavicular lymph node (LN) is relatively rare. Moreover, cases of metastatic RCC with a non-identifiable kidney mass are extremely rare. Here, the authors report a case of metastatic RCC in a supraclavicular LN without a primary kidney lesion. A 69-year-old man presented with a progressively enlarging right supraclavicular mass. Incisional biopsy of the affected supraclavicular LN was performed, and histological examination revealed metastatic RCC. However, no tumor was found in either kidney, despite various examinations. The patient was treated with radiotherapy followed by sunitinib. After three months on sunitinib, a follow-up computed tomography scan revealed that the supraclavicular LN had markedly decreased, and after 20 months, the disease had not progressed. This case suggests that, even when there is no primary kidney lesion, clinicians must consider the possibility of metastatic RCC when evaluating patients with clear cell carcinoma with an unknown primary site.