Small Cell Carcinoma Presenting with Massive Pleural Spread Mimicking Malignant Pleural Mesothelioma

: Small cell carcinoma (SCC) predominantly spreading over the pleura is exceedingly rare and difficult to diagnose without proof of malignant effusion. A 65-year-old man presented with right pleural thickening and effusion and was diagnosed with SCC based on a thoracoscopic pleural biopsy. He received combined chemotherapy consisting of cisplatin and irinotecan hydrochloride, which resulted in a complete response. Seven months later, local relapse was observed. Thereafter, he received second-, third- and fourth-line chemotherapies and died of tumor progression 21 months after the diagnosis. Considering the possibility of SCC with pleural spread, performing early invasive procedures is important for diagnosing pleural malignancies.