Mature Teratoma Revealed by an Encysted Pleural Effusion

A 32-year-old patient with no previous history was admitted for chest pain, dyspnea, appetite and weight loss. Chest X-ray revealed an opacity involving the lower two-thirds of the right hemithorax, suggestive of a pleural effusion. Because of the absence of fluid return even after ultrasound-guided thoracentesis, a Chest Computed tomography was required showing a heterogeneous anterior mediastinal mass with soft tissue, fat, fluid and calcifications associated with extensive encysted fluid collection in the right hemithorax. A video-assisted mini-thoracotomy revealed a mediastinal tumor firmly attached to the thymus with a cystic wall lined by squamous epithelium and sebaceous gland composed of respiratory tissue, adipose tissue, cartilage, smooth muscle fibers, and well-differentiated pancreatic tissue. These findings led to the diagnosis of a mature thymic teratoma. The patient was discharged 7 days after surgery, with no recurrence on follow-up.