A 71-year-old female with a history of a resected sarcoma of the chest wall presented for a follow-up examination 34 months after surgery. She had undergone wide excision of a soft tissue mass on the right chest wall in January 2004. The mass, together with involved intercostal muscles, ribs (fifth and sixth), and pleura was resected en bloc. Defects of the chest wall were repaired using Prolene mesh. Postoperative pathological diagnosis revealed low-grade fibroblastic/myofibroblastic sarcoma involving skeletal muscle, ribs, and pleura. On immunohistochemical staining, the tumor was negative for actin, desmin, CD34, cytokeratin and S-100, except for CD99. Her postoperative course was uneventful, and she received no postoperative adjuvant therapy. At her follow-up visit in November 2006, she presented with a 3-month history of a progressively enlarging mass on the right chest wall. Physical examination was significant for a large mass measuring 10×7 cm on the right chest wall with a well-healed scar. CT revealed a large chest wall mass (maximum diameter=11 cm, Fig.1). Distant metastasis was excluded with a preoperative evaluation, and en bloc resection was then planned. Exploratory surgery revealed that the tumor had invaded the pectoralis major, ribs, intercostal muscle, pleura and lung. En bloc resection involving the pectoralis major, ribs four to seven, partial lung (middle and lower lobe) was performed. The chest wall was reconstructed with Marlex mesh and a latissimus flap. Pathological examination of the specimen revealed a LGMS involving skeletal muscle, ribs, pleura, and lung. Immunohistochemically, the tumor was positive for smooth muscle actin, desmin, CD34, CD99 and actin, but negative for cytokeratin, epithelial membrane antigen, fibronectin, and HBME1(Fig.2). The patient received no postoperative treatment and felt well 9 months after the second operation.