Osteosarcoma in the coracoid process that mimicked an osteochondroma

RATIONALE Osteosarcomas are the most common primary malignant bone tumors in children and young adults; these tumors often affect the metaphyses of long bones such as the proximal humerus, proximal tibia, and distal femur. In contrast, osteosarcoma of the coracoid process is extremely rare. PATIENT CONCERNS Herein, we describe a case of osteosarcoma affecting the coracoid process in a 40-year-old woman. The patient presented with shoulder pain, weakness, and an inability to raise her left arm. She had no previous record of shoulder injury and no significant family history. DIAGNOSES Her C-reactive protein levels were normal, whereas her erythrocyte sedimentation rate and alkaline phosphatase levels were elevated. Imaging studies led to the initial diagnosis of osteochondroma. INTERVENTION The patient underwent surgical resection. However, the postoperative pathological results revealed an osteosarcoma. The patient transferred to another hospital for subsequent treatment, and her outcome is unknown. LESSONS A misdiagnosis or inadequate and/or delayed treatment for a coracoid process osteosarcoma could have grave consequences. Computed tomography and magnetic resonance imaging are essential for a diagnosis, and a biopsy can effectively confirm the diagnosis. Our findings suggest that considering only a single factor, or using incomplete information, can lead to an arbitrary diagnosis.