[A monstrous tumour in the thorax can represent a thymoma]

Pulmonary infiltrates on radiological imaging are most often assumed to be a potential lung cancer, although seldom, other malignant intrathoracal tumours can appear. Knowledge of these, their growth pattern and localisation is of significance in order to reach a differential diagnosis and to plan targeted treatment. In mediastinum anterior thymoma is the most frequent form of cancer arising from the thymus epithelium. This case report describes a male patient suspected of lung cancer who happened to have malignant thymoma with atypical dissemination, which challenged the diagnostics.