Cutaneous Metastasis of Renal Cell Carcinoma

Summary: Renal cell carcinoma (RCC) is a complex malignancy with aggressive potential that can metastasize to the lungs, liver, bones, and regional lymph nodes. Cutaneous metastases of RCC are exceedingly rare, occurring in less than 1% of cases. Herein, we discuss a 70-year-old male smoker with Stage IV RCC who presented with a rapidly enlarging, tender scalp nodule. The patient had previously undergone complex anti-cancer therapy including left nephrectomy with adrenalectomy and radiation, with lung, liver, and bone metastases treated with multiple lines of chemotherapy. Physical examination demonstrated a 2.5 cm x 2.4 cm well-circumscribed and dome-shaped violaceous nodule with hemorrhagic crust and numerous telangiectasias at the base. There was no cervical or occipital lymphadenopathy. Histopathologic examination of a shave biopsy demonstrated a proliferation of large clear cells arranged as clusters and sheets within the dermis, associated with a prominent vascular component. The neoplastic cells were positive for PAX-8 and carbonic anhydrase IX , and negative for CK7. Given evidence of overt progression, patient started on belzutifan, and is undergoing continued management. This case highlights a rare presentation of RCC with cutaneous involvement, emphasizing the importance of recognizing metastatic lesions in the skin as these lesions may herald systemic disease progression.