CLINICAL VISTAS P RACTICE An unusual cause of and

54-year-old woman was re- A ferred to the service for evaluation of thyro- megaly detected incidentally on physical examination. She was at the time, but 48 months earlier she had been found to have estrogen/proges- terone receptor-negative infil- trating ductal breast carcinoma and had known bone . On examination, her was diffusely enlarged to about needle aspiration or thyroidec- 3 times normal size and was tomy is required for definitive firm and nontender with no dis- diagnosis.3 tinct nodules. The remainder of Although destructive thy- her examination was unremark- roiditis leading to transient hy- able. Her thyroid stimulating perthyroidism in patients with (TSH) level was nor- thyroid metastases has been de- mal (2.5 mIU/L); free thyroxine scribed,4 hypothyroidism due to was not measured, and antithy- thyroid metastases is extremely roid peroxidase and antithy- rare. In addition to causing the roglobulin antibody levels were received palliative radiotherapy thyroid enlargement and nodule not elevated. Ultrasonography to the . She noticed a tran- formation, we believe that the of the neck showed both thy- sient improvement in her thyroid metastases were respon- roid lobes enlarged, with isoe- symptoms but succumbed 2 sible for our patient’s hypothy- choic nodules (3.6 × 2.2 × months later to her progressive roidism, because she became 2.0 cm) in each lobe and lymph- metastatic disease. significantly hypothyroid in a adenopathy in inferior jugular short period and had negative chains bilaterally. Fine-needle antithyroid antibody levels. aspiration of one of the nodules Metastases to the thyroid gland Physicians should consider and a lymph node revealed ma- are uncommon, with a reported the possibility of metastatic dis- lignant cells in an inflammatory prevalence of 0.5%–2% in all ease to the thyroid when evalu- background consistent with cancers.1 The most common ating patients with evidence of metastatic carcinoma (Fig. 1A). malignant diseases to metastasize thyroid dysfunction, particularly The cells had similar features to the thyroid include breast, if they have a history of malig- to cells from a previous fine- lung and renal cell carcinoma. nant disease. needle aspiration of breast car- Such metastases generally occur cinoma performed when cancer in the setting of widespread Hasnain M. Khandwala was first diagnosed (Fig. 1B). known metastatic disease, but Division of Endocrinology The patient experienced involvement of the thyroid may Department of Medicine progressive , hoarse- be the initial manifestation of an Rajni Chibbar Department of Pathology ness of voice and weight loss underlying malignant disease.2 University of Saskatchewan over the next few months, and a Thyroid metastases may either Saskatoon, Sask. CT scan taken 4 months after be asymptomatic or present with the initial assessment showed diffuse or nodular goitre, pain or References significant thyromegaly with symptoms such as dysphagia, 1. Watts NB. Carcinoma metastatic to encasement of the (Fig. stridor and hoarseness of voice the thyroid: prevalence and diagnosis by fine-needle aspiration. Am J Med 2). The TSH level was elevated arising from compression of the Sci 1987;293:13-7. (56 mIU/L) and the free thyrox- esophagus, trachea and recurrent 2. Gandhi A, Banerjee SS, Bhatti WA, ine level was 6.6 (normally laryngeal nerves respectively. El-Tereifi H, Bundred NJ. Carcinoma of the breast presenting as a thyroid 9.0–19.0) pmol/L. These find- Mean survival after detection of mass. Eur J Surg 1997;163:871-3. ings were consistent with hypo- metastases to the thyroid has 3. Ivy HK. Cancer metastatic to the thy- roid; a diagnosis problem. Mayo Clin thyroidism, and the patient was been reported to be 5 months. Proc 1984;59:856-9. given . Her TSH Differentiation between benign 4. Miyakawa M, Sato K, Hasegawa M, level 4 weeks later was , primary thyroid Nagai A, Sawada T, Tsuishima T,et al. Severe thyrotoxicosis induced by 2.4 mIU/L. She was not con- cancer and metastases can be thyroid metastasis of lung adenocarci-

DOI:10.1503/cmaj.1040448 sidered a surgical candidate and challenging, and either fine- noma. Thyroid 2001;11:883-8.

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