Abstract
We report a case of primary clear cell sarcoma occurring in the humerus. A 20 year old girl was referred to our hospital two years ago with painless swelling of the soft tissue surrounding the proximal right humerus. The conventional radiographic image showed an ill-defined, aggressive, osteolytic lesion associated with a partial cortical defect of the proximal right humerus. Magnetic resonance imaging found an irregularly shaped extraosseous mass extending from the proximal shaft of the right humerus, penetrating through the destroyed bone and invading the biceps brachii. After preoperative chemotherapy, a total tumor resection, internal fixation and bone cement implantation were performed. Histological studies of the resected tumor found that fibrous septa divided into well-defined nests and polygonal and fusiform cells with clear cytoplasm. Immunohistochemical studies demonstrated strong positive cytoplasmic staining with S-100 and scattered positivity with HMB-45. These findings led to a final, definitive diagnosis of clear cell sarcoma of the humerus. After routine postoperative chemotherapy, a 2-year follow-up showed no metastasis. Our findings in this report point out that primary clear cell sarcoma can originate from within the humerus and that limb salvage surgery can obtain a good result.