Unexpected diagnosis of thymic small cell carcinoma following acute respiratory distress

Thymic small cell carcinoma (TSCC) is an exceptionally rare and aggressive extrapulmonary neuroendocrine malignancy. We report a man in his 60s presenting with acute respiratory distress while receiving antibiotics for presumed aspiration pneumonia.Chest CT excluded pulmonary embolism but revealed anterior and paracardiac mediastinal masses. Thoracoscopic resection of the paracardiac mass unexpectedly confirmed small cell carcinoma of thymic origin. 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/CT scan showed a hypermetabolic anterior mediastinal lesion and a suspicious right upper lobe nodule, without distant metastases. The disease was staged Masaoka-Koga IIB (cT3N1M1b). Combined chemoradiotherapy led to radiological regression after 3 months.TSCC is a high-grade, aggressive neoplasm that is frequently misdiagnosed because of its non-specific presentation. This case underlines the importance of considering rare thoracic malignancies in acute settings. It illustrates the key role of early histological diagnosis, multidisciplinary evaluation and multimodal therapy in the management of extrapulmonary small cell carcinomas (EPSCC).