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.