Anaplastic thyroid carcinoma (ATC) is a particularly fearsome form of thyroid cancer due to its extreme aggressiveness and dismal prognosis. Patients with ATC typically present with a rapidly enlarging neck mass with compressive symptoms. We report a case of ATC, mimicking a thyroid abscess; in a 52-year-old Chinese male with one month history of enlarging neck mass. Ultrasound of the neck was suggestive of a thyroid cyst and fine needle aspiration cytology was negative for malignancy. He presented again 2 weeks later with increased swelling and pain suggestive of right neck abscess. An incision and drainage was performed and histopathology result of a proximal isolated enlarged lymph node biopsied revealed metastatic carcinoma. Subsequent right thyroid wedge biopsy finding 1 month later were confirmatory of ATC.
