Severe Thyrotoxicosis Induced by Thyroid Metastasis of Lung Adenocarcinoma: A Case Report and Review of the Literature

Abstract

A 50-year-old woman who had undergone lung lobectomy because of lung adenocarcinoma presented with thyrotoxicosis, neck swelling, and cervical lymphadenopathy one month after the operation. The total serum triiodothyronine (T3) and thyroxine (T4) levels were markedly elevated to 514 ng/dL and 26.4 microg/dL, respectively, and serum thyrotropin (TSH) was suppressed to less than 0.005 microU/mL. Although the thyroid gland had been normal before surgery, chest computed tomography (CT) scan revealed a markedly enlarged thyroid gland only 1 month after surgery. 123I uptake for 24 hours was suppressed to 4% in the thyroid gland with no uptake elsewhere including the lung. Fine-needle aspiration cytology (FNAC) of the thyroid showed invasion of poorly differentiated adenocarcinoma cells, cytologically identical to the cells obtained from sputum and those infiltrating the resected sections of the lung adenocarcinoma. Immunohistochemical studies of resected lung tissues did not show positive staining for thyroglobulin, carcinoembryonic antigen (CEA), or surfactant protein A. Clinically, the thyrotoxicosis had spontaneously improved, followed by a hypothyroid state with shrinkage of the thyroid gland after chemotherapy. Despite repeated chemotherapy and the administration of thyroxine for hypothyroidism, the patient died of respiratory failure 9 months after the onset of thyrotoxicosis. From these findings and the clinical course, thyroid metastasis, developing subacutely from lung adenocarcinoma, was diagnosed. We speculate that aggressive invasion of tumor cells into the thyroid gland resulted in highly destructive thyrotoxicosis.

Diffuse Thyroid Enlargement Following Metastasis of Lung Adenocarcinoma

“…In addition to the ultrasonographic findings noted in this case, contrast-enhanced CT showed reticular cord-like structures. Therefore, in association with ultrasound, CT examinations may provide valuable information for arriving at a definitive diagnosis, although previous studies (6,8,11) did not mention CT findings. One past study reported the high diagnostic accuracy of FNAB for detecting secondary thyroid tumors, particularly those in cases of lung cancer metastasis (1, 7).…”

Severe Hypothyroidism Induced by Thyroid Metastasis of Colon Adenocarcinoma: A Case Report and Review of the Literature

“…The average survival after the diagnosis of metastatic thyroid carcinoma with thyroid dysfunction was much shorter, i.e. 3 to 16 months [11], compared to the cases without any functional change.…”

“…Recently, only 4 cases were reviewed that developed transient thyrotoxicosis caused by massive metastasis of an extrathyroid tumor, such as breast cancer, lung cancer or pancreatic carcinoma [11]. The term "malignant pseudothyroiditis" has been described in a few cases of primary or secondary thyroid cancer presenting with clinical and often biochemical features of subacute or chronic thyroiditis [19].…”

“…Only 12 cases of metastasis from colon cancer to the thyroid have been reported since 1936 [4][5][6][7]. Currently there are only 5 cases of thyroid dysfunction caused by metastatic cancer infiltration [8][9][10][11][12]. Most of the manifestations were thyrotoxicosis followed by destruction.…”

An unusual cause of goitre and hypothyroidism

“…Differentiation between benign thyroid disease, primary thyroid cancer and metastases can be challenging, and either fineneedle aspiration or thyroidectomy is required for definitive diagnosis. 3 Although destructive thyroiditis leading to transient hyperthyroidism in patients with thyroid metastases has been described, 4 hypothyroidism due to thyroid metastases is extremely rare. In addition to causing the thyroid enlargement and nodule formation, we believe that the thyroid metastases were responsible for our patient's hypothyroidism, because she became significantly hypothyroid in a short period and had negative antithyroid antibody levels.…”