This is a report of an unusual anaplastic thyroid carcinoma case with capsule and long disease-free survival. This 74-year-old male, with an asymptomatic nodule in the mid-line neck for 5 years, was treated with total thyroidectomy. Light microscopy and immunohistochemistry showed an anaplastic carcinoma of the thyroid isthmus. There were no signs of carcinoma elsewhere either at the time of surgery or 35 months later, when the patient was last seen.