Benign and malignant lesions of the thyroid gland and its adjacent structures may present clinical, biochemical and radio-active scan features resembling subacute thyroiditis. An irregular clinical course, unexpected laboratory findings and unresponsiveness to medical treatment may indicate the true nature of the disease. Whenever a subacute or chronic thyroid inflammatory process is diagnosed, the possibility of benign or malignant lesions of the thyroid or of the surrounding organs should be kept in mind. If doubt is raised, further investigations should be carried out if indicated including exploratory surgery.