Chondromyxoid Fibroma with Secondary Aneurysmal Bone Cyst of the Rib

Chondromyxoid fibroma (CMF) is a rare, benign cartilaginous tumor, comprising less than 1% of primary bone tumors, and usually occurs in the metaphysis of a long tubular bone around the knee. We report a rare case of CMF of the rib. The patient was a 25-year-old man who visited the hospital for left upper back pain. Roentgenography revealed an 8-cm mass in the left upper lung field; computed tomography revealed a large multicystic tumor with aneurysmal bone cyst (ABC)-like features in the posterior mediastinum. ABCs are also a rare benign tumor representing 2.5% of primary bone tumors, and most of ABCs are located in the metaphysis of long bones and vertebrae. To the best of my knowledge, there is no report of CMF with secondary ABC of the rib. We performed total resection of the tumor. Complete tumor resection may be the best treatment option for a cure.