Radiological criteria such as smooth, sharply defined interface, obtuse angles between lesion and lung and intimate effect on mediastinal contents were usually used to differentiate mediastinal lesion from parenchymal lung lesion. Recently, we experienced a 60-year-old female presenting with anterior mediastinal mass with cavitation. Grossly it was proven to be peripheral lung cancer adjacent to mediastinum and microscopically it was squamous cell carcinoma. The gross pathological findings of surgical specimen were very well correlated with radiological findings. The unique location such as lung periphery and attachment to mediastinum led us to misdiagnosis of anterior mediastinal mass such as germ-cell tumor and neurogenic tumor.