Fig. 4

The histopathological findings of the resected cystic tumor. A pedunculated cystic tumor was connected to the pleura with a stalk (white arrow head), and white polypoidal masses were found within the cystic tumor (a). Uniform fibroblastic spindle cell proliferation and marked cystic degeneration were found; all cyst walls were formed of the same tumor cells (b). Immunohistochemical staining revealed that the tumor cells were positive for STAT6, CD34 (c, d)