[Successful operation for two cases of an aneurysmal bone cyst of the rib].

An aneurysmal bone cyst involving the rib is very rare. A 43-year-old man and 49-year-old woman complained of pain and swelling on the chest. X-ray and CT revealed a local expansion and honeycomb lesion of the right 9th rib. Surgical excision of the rib were performed to remove the tumor completely. The histopathological examination revealed that the lesion consisted of many cavities filled with blood and trabecullae containing osteoid tissue and giant cells, showing it to be an aneurysmal bone cyst. Because of the potential for the rapid growth and difficulty in differentiation between benign and malignant rib tumor, an excisional biopsy should be considered for the treatment of an aneurysmal bone cyst of the rib.