A 59 year old woman presented with diffuse thyroid enlargement and symptoms of thyrotoxicosis. Following initial management with carbimazole a total thyroidectomy was performed. Microscopically thyroid gland showed features of a multinodular goitre and a hyperplastic nodule. In multiple foci the follicular epithelial cells displayed increased nuclear to cytoplasmic ratio, pleomorphic and hyperchromatic nuclei. Occasional bizarre forms were evident. Such cytological atypia is seen in atypical follicular adenoma, follicular carcinoma with anaplastic transformation, Hashimoto thyroiditis and treatment with radioactive iodine. In this case, histological evidence of such pathologies was not seen. Radioactive iodine was not given. Carbimazole treatment is attributed to the cytological atypia.