Undifferentiated metastatic renal cell carcinoma presenting as a cutaneous nodular lesion.

Cutaneous metastases may be the first sign of clinically silent visceral cancer. Approximately 30% of patients with primary renal cell carcinoma present with metastatic disease, and only 8% of them have skin metastases. We present the case of a 59-year-old male patient with a subcutaneous nodular on the upper chest extending to the jugular region. The lesion appeared skin colored and was not painful and 5 cm × 3.5 cm in diameter. The histological examination of the cutaneous biopsy showed an infiltration of undifferentiated epithelial cells positive to cytokeratins AE1/AE3, whereas they were negative to CK-20, CK5/6, cluster of differentiation 10, vimentin, thyroid transcription factor-1, S-100, human melanoma black-45, hepatocyte-specific antigen, carcinoembryonic antigen, and chromogranin A. A total-body computed tomography (CT) showed the presence of a tumoral lesion in the left kidney with multiple metastases in the lung, brain, and bones. According to the cutaneous biopsy and total-body CT, a final diagnosis of an undifferentiated renal carcinoma presenting as a subcutaneous metastasis was made. A chemotherapeutic treatment with gemcitabine and cisplatin resulted in the stabilization of the renal and metastatic lesions with an improvement in the quality of life of the patient. Considering that the prognosis of patients with cutaneous metastases is very poor, it is necessary to obtain an appropriate diagnosis in order to identify patients with treatable disease with the purpose of starting a therapeutic protocol.