Case Description
A 53-year-old woman, treated with 10 mg of thiamazole for postoperative recurrence of hyperthyroidism, was referred to our department for further investigation of neck goiter (Figure A ). The patient had normal thyroid function (free T3: 2.64 pg/mL, free T4: 0.80 ng/dL, and TSH: 3.73 U/mL) and tested negative for TSH receptor antibodies (TRAb). However, the serum thyroglobulin level was elevated (982 ng/mL). Echocardiography and computed tomography revealed multiple nodules in the thyroid glands (maximum nodule diameter: 30 mm). Tc-99m scintigraphy showed a hot nodule in the left lobe that was consistent with a functional nodule, in addition to cold nodules (Figure B ). Pathological examination after subtotal thyroidectomy revealed right papillary carcinoma and a left adenomatous nodule.
Toxic multinodular goiter (TMNG) refers to typically benign nodules in the thyroid gland that autonomously secrete excessive amounts of thyroid hormones and is one of the primary causes of hyperthyroidism or thyrotoxicosis. Up to 15% patients with nodules have neoplastic changes1. TMNG may be characterized by a mixture of functional and nonfunctional adenomas. A radionuclide scan is useful for identifying the functional status of these nodules. Hot nodules are hyperfunctioning nodules, while cold nodules indicate defects in the secretory function. Coincidental carcinomas with TMNG have been rarely reported, whereas a recent study revealed that hot and cold nodules have the same risk of malignancy2. Therefore, diagnosis should not be based solely on radionuclide images. Physicians should recognize that the most surefire treatment of MTNG is surgical excursion and consider the possibility of malignancy by comprehensive evaluation of imaging studies.