A 40-year-old woman had a swelling over the medial end of the right clavicle and a nodule in the left lobe of the thyroid. There was greatly increased activity in the clavicular swelling. Cytologic analysis of a fine-needle aspiration from the thyroid and clavicle showed follicular carcinoma. Total thyroidectomy and segmental excision of the right clavicle was done. Histopathologic analysis revealed a poorly differentiated carcinoma with insular features. This supports the concept that insular carcinoma is a functional follicular carcinoma with good I-131 uptake.