Fig. 2

a Intraoperative findings showing adhesion of the tumor (arrow) to the ascending aorta (circle) after resection of the pericardium and right upper lung. The bilateral lungs are marked with triangles and the right auricle is marked with a square. b The tumor consisted of an 85 × 55 mm solid mass and a 90 × 50 mm cystic mass with severe adhesion to the resected portion of the lung, which included skin and lipid tissue. c Hematoxylin–eosin staining of the tumor specimen demonstrating that the inner cavity of the cystic tumor was lined mainly with skin, which was composed of keratinized squamous epithelium, sebaceous and sweat glands, hair follicles, and smooth muscle. The tumor also contained adipose tissue and bronchial elements. The wall of the tumor demonstrated necrotizing inflammation, with the infiltration of many neutrophils, lymphocytes, and macrophages. Neither an immature component nor malignant transformation was observed (low power magnification)