Multiple circular pleural metastases of renal cell carcinoma

A 91-year-old woman was admitted with persistent pyrexia, anorexia and weight loss. A chest radiograph showed multiple circular masses of various sizes. Chest computed tomography revealed multiple pleural tumors without any lung lesion. The ultrasound-guided biopsy specimens demonstrated diffusely-proliferated tumor cells with clear or vacuolated cytoplasm, which were positive for CD10, PAX8, vimentin and CAM5.2, but were negative for mesothelial cell markers such as HBME-1 and thrombomodulin. These findings indicated metastatic clear cell carcinoma of the kidney, and a solitary renal tumor was observed on abdominal computed tomography. It has been reported that pleural metastases constituted 12% of patients with progressive renal cell carcinoma, and most of the pleural metastases occurred secondary to lung metastasis. This was a rare case of renal cell carcinoma with an unusual chest image via an intriguing metastatic pathway, which was limited to pleura.