A 24-year-old patient who developed pulmonary metastasis of metachronous triple cancer was presented. She had undergone surgery and combined chemotherapy for osteosarcoma of the right humerus in 1993. Then, she was followed-up without any sign of recurrence. She felt accidentally a lump of the right breast so she had visited a hospital for a work-up in 2004. The detailed examination proved that the right breast mass was primary breast cancer so the right mastectomy was carried out. Moreover, the left mastectomy was also carried out for the primary breast cancer in 2005. Additionally, a solitary nodule shadow was detected by computed tomography in 2007 so she had thoracoscopic partial resection of right middle lobe. Histopathologically, the tumor was diagnosed metastasis from the left breast cancer. It is unlikely that familial cancer disease was the underlying cause because she had no family history of cancer. A more likely explanation is that there is the influence of combined chemotherapy during puberty.