This case report describes the development of a post-treatment enlargement of the sternoclavicular joint, diagnosed as a pseudo-tumour, in a patient who had previously undergone radical neck dissection and post-operative radiotherapy for metastatic mucoepidermoid carcinoma. Although pseudo-tumour has been previously reported in the surgical literature, it remains an uncommonly recognized condition. We present a review of the literature and discuss the condition's pathogenesis. We also highlight its importance to both the surgeon and the oncologist when considering the differential diagnosis of a swelling in the clavicular region, typically occurring following radical surgery for malignant disease in the neck.