Differential diagnosis of primary intrapulmonary thymoma: a report of two cases.

Primary intrapulmonary thymomas (PITs), which are intrapulmonary tumors without an associated mediastinal component, are very rare. The diagnosis of a PIT can be difficult. Here, we report two cases of resected PITs that were difficult to differentiate from other lung tumors. The patients, of a 62-year-old man and a 64-year-old woman, had no significant symptoms and were both referred to our hospital due to the presence of an abnormal shadow on chest computed tomography (CT). The patients underwent (18)F-fluorodeoxyglucose positron emission tomography-CT (FDG-PET/CT) and subsequently tumor excision. A PIT was confirmed histopathologically in the surgical specimens from both patients. In one case, the tumor consisted of a type A thymoma without abnormal FDG uptake. In the other case, the tumor consisted of a type B2 thymoma presenting with weak FDG uptake. This report thus documents two cases of PITs with different histopathologic and FDG-PET/CT findings. Thoracoscopic surgery is essential in the differential diagnosis between PITs and other lung tumors.