Summary

A 19-year-old man presented to the emergency department with a 3-week history of chest pain. Despite normal examination, bloods and observations of his chest X-ray revealed a large opacity in the middle and lower right zone. Further imaging revealed a multicystic mediastinal teratoma. He was admitted under the respiratory physicians who arranged further investigations and discussed his case with the lung and testicular multidisciplinary team. He was started on neoadjuvant chemotherapy with a plan for future definitive surgical resection. Four months later he suddenly deteriorated due to airway compression from the tumour. He underwent an emergency thoracotomy and tumour resection. He is currently doing well and is thought to have a good prognosis following complete resection of his tumour. This case report summarises this rare diagnosis and emphasises the need for careful evaluation of patients despite their initial well appearance, especially in patients who are reattending.