An Unusual Presentation of Chondrosarcoma of the Clavicle With Horner's Syndrome

We report a unique case of symptomatic chondrosarcoma of the medial end of the clavicle resulting in pain and Horner’s syndrome. To our knowledge this is the first reported case in the literature of Horner’s syndrome secondary to a clavicular tumour. Osteochondroma, a frequent benign tumour of the bone, is in many cases asymptomatic. The reported risk of malignant transformation in a solitary osteochondroma is approximately 1%. Localisation in the clavicle is extremely rare. The lesion in this case was primarily an osteochondroma that underwent malignant transformation becoming symptomatic.