Minimally Invasive Resection of an Intrathymic Bronchogenic Cyst Presenting as a Thymic Neoplasm

Abstract

INTRODUCTION: Bronchogenic cysts are developmental anomalies of the ventral foregut arising from abnormal budding of the primitive tracheobronchial tree. Usually they acquire an intra-thoracic location primarily mediastinal or intraparenchymal, though atypical locations including cervical, intradiaphragmatic, interatrial septum and retroperitoneal have been reported. We present an extremely rare, aberrant location of a bronchogenic cyst within the thymic tissue that was minimally resected with robotic assistance. CASE PRESENTATION: A 45 year old previously healthy male presented with shortness of breath, wheezing, productive cough and hypoxia on initial examination. Chest X-ray was normal and was followed by a CT angiogram to rule out a pulmonary embolism. The scan revealed an anterior mediastinal mass measuring 3.3x1.8x2.1cm consistent with a thymic neoplasm. Surgical resection was planned and the patient underwent a right-sided robotic-assisted thymectomy and lymphadenectomy. Pathological examination revealed an intra-thymic bronchogenic cyst present in the right side of the thymus filled with serous fluid. Histologically, the lining wall of the cyst was composed of respiratory type epithelium with focal squamous metaplasia. DISCUSSION: Bronchogenic cysts developing within the thymus are extremely rare entities with less than five reported cases in the English literature [1]. The mechanism is not completely understood. Bronchogenic cysts are usually fluid filled and the variability of the cyst content results in soft tissue attenuation on computed tomography [2] leading to a misdiagnosis of thymoma. We advocate minimally invasive surgical excision when identified due to their potential for malignant transformation [3] regardless of the presenting symptoms. CONCLUSIONS: Intra-thymic bronchogenic cysts are very rare and should be considered in the differential of an anterior mediastinal mass. Minimally invasive resection is ideal for these benign lesions.