Medical thoracoscopy performed under local anesthesia is useful for diagnosing pleural metastasis of renal cell carcinoma.

A patient with a past history of renal cell carcinoma (RCC) presented to us with an exudative pleural effusion. Because pleural effusion cytology was inconclusive, we performed medical thoracoscopy under local anesthesia. Multiple white tumors measuring approximately 2 cm in diameter were observed on the parietal pleura. Metastatic carcinoma from RCC was diagnosed histologically. Although malignant effusions are rare in cases of RCC metastasis, clinicians should be aware of this possibility. When pleural effusion cytology is inconclusive in a patient with a past history of RCC, medical thoracoscopy can be useful for making the diagnosis of pleural metastasis.