Extra capsular bleeding occupies a particular place within the evolutional complications of parathyroid tumors. Its rarity, the difficulty of the pre-operative diagnosis and its potential evolution towards airway obstruction by compression underline its singular character. A case is presented where an evolutive cervico-thoracic hematoma, evolving without functional symptoms, has led to the diagnosis of parathyroid hyperplasia. The diagnostic and therapeutic characteristics of this pathology are detailed and confronted to the similar cases found in the literature.