Fig. 1

Computed tomography findings. a Retrospectively, chest computed tomography image which was taken before the previous operation shows not only cyst which was resected but also a small nodule (arrow) which was not resected at the anterior mediastinum. b Chest computed tomography imaging which was taken before the present operation shows heterogeneously enhancing mass at the anterior mediastinum. The mass seems to grow from the previously existed small nodule