Chest tumour. Frontal X-ray of a large tumour (white mass at centre right) in a patient's thoracic cavity. This is a mediastinal tumour, it is in the cavity that separates the lungs (the mediastinum) and contains the heart (Centre). The tumour is benign (non- cancerous). Mediastinal tumours are rare and generally cause no symptoms. However, tumours of this size may cause coughing, shortness of breath and chest pain. Treatment is with surgical removal of the tumour.