A 44-year-old woman who had undergone hystero-oophorectomy for uterine sarcoma presented to our hospital with palindromic pneumothorax and her chest CT revealed multiple cystic lesions. After admission video-assisted thoracoscopic surgery (VATS) showed the pulmonary lesions to be primarily leiomyoma, however, further examination revealed that her uterine sarcoma resected in 2000 exhibited not only mitosis but also venous invasion. We therefore considered her lung tumors as metastases from uterine leiomyosarcoma. Cases of secondary spontaneous pneumothorax (SSP) due to pulmonary metastases are rare and almost half are from mesenchymal tumors. Thin-wall cavities and cysts are formed by a check-valve mechanism in the process of pulmonary metastases formation. When multiple thin-wall cavities and cysts are found in the lung, pulmonary metastases should be considered as one of the causes, and pathological specimens obtained in past illness should be re-examined in detail.