Identifying Hereditary Leiomyomatosis and Renal Cell Cancer through Unobtrusive Cutaneous Nodules: A Clinical Report.

Cutaneous small vessel vasculitis (CSVV) is an immune-mediated inflammatory disorder affecting the small dermal vessels and is often linked to autoimmune diseases, infections, or malignancies. Renal cell carcinoma (RCC), a common urologic malignancy, rarely presents with CSVV as a paraneoplastic manifestation. This case describes a 68-year-old woman with a history of left radical nephrectomy for clear cell RCC who presented with persistent flank pain and progressive purpuric, painful lesions on her lower limbs. Imaging revealed recurrent metastatic disease in the left retroperitoneum with inferior vena cava (IVC) involvement and a hypermetabolic right supraclavicular lymph node. Skin biopsy demonstrated neutrophilic infiltration and features of leukocytoclastic vasculitis, while immunohistochemistry confirmed the paraneoplastic nature of the vasculitis with positivity for IgM, vimentin, and cytokeratin. Initiation of sunitinib therapy resulted in significant improvement of the cutaneous lesions and tumor regression, followed by successful tumor debulking and IVC reconstruction. This case underscores the importance of considering paraneoplastic vasculitis in the differential diagnosis of new or atypical skin manifestations in patients with a history of RCC. Timely recognition and targeted therapy can improve outcomes and provide valuable insights into the broader systemic impact of malignancies like RCC.