Radiographs can be misleading as well. Prior studies have demonstrated that low-grade central OS can be readily misdiagnosed as fibrous dysplasia, desmoplastic fibroma, nonossifying fibroma, osteoblastoma, and aneurysmal bone cyst.6 Findings found in low-grade OS can include evidence of cortical interruption, local soft tissue mass development, intramedullary involvement, cortical destruction, and poor margination; however, low-grade OS is typically sclerotic and highly trabeculated. Cross-sectional imaging can help differentiate between OS and other more benign pathologies and should be considered in the clavicle where biopsy may be perilous. 5The difficulty of clavicular biopsy has been reported. Not only does clavicular anatomy make biopsy hazardous, but also the potential for sampling error does exist. In a case report of one patient with a highgrade lesion, fine needle aspiration biopsy was initially diagnosed as an aneurysmal bone cyst but was ultimately found to be osteosarcoma. 2 Histology of low-grade lesions usually demonstrates minimal cytological atypia, rare mitotic activity, and variable osteoid production. 5 Lower mitotic indices typically make wide resection curative for these patients, without the need for chemotherapy.
In this case, wide resection was carried out with the subclavian vein as the posterior-inferior margin and the sternoclavicular joint as the medial margin. Though the intra-operative medial margin was clear of disease, final pathology demonstrated focal (microscopic) involvement of the posterior and medial margins. A study of soft tissue sarcoma evaluated positive margins and concluded that the imperative of preservation of vital structures supersedes the need for negative margins. 7,8 The rate of metastasis and overall survival was similar to surgical resections with positive margins. In the case of our patient, further resection would have carried significant morbidity and possibly mortality, including sacrifice of the major vessels to the arm below and entering into the sternum and thoracic cavity. The likely disability as well as the hazards of surgery were deemed to be too great to justify further excision. Frequent cross-sectional imaging will be necessary to evaluate the presence of recurrent or metastatic disease. To our knowledge, this is the first documented case of low-grade clavicle OS. This report demonstrates the need for multidisciplinary sarcoma care at a center of excellence, particularly in instances of unusual diagnoses.