New-onset thyrotoxicosis in a patient with anaplastic thyroid carcinoma: a diagnostic challenge

Abstract

Summary: Anaplastic thyroid cancer (ATC) is the type of thyroid cancer that has the worst prognosis. It usually presents as a rapidly growing cervical mass that generates compressive symptoms. Its association with thyrotoxicosis is rare. A 76-year-old woman, with no contributory history, presented with a 3-month course of fast-growing cervical tumor, associated with tenderness, cough, and weight loss. Physical examination revealed goiter, localized erythema, and a painful and stone tumor dependent on the right thyroid lobe. Due to the malignant findings of the thyroid ultrasound, the patient underwent a thyroid core needle biopsy, which indicated ATC. Laboratory tests revealed leukocytosis, decreased thyroid-stimulating hormone, elevated free thyroxine (fT4), and increased thyroperoxidase (TPO) antibodies. At the beginning, we considered that the etiology of thyrotoxicosis was secondary to subacute thyroiditis (SAT) after SARS-CoV-2 infection, due to the immunochromatography result and chest tomography findings. The result of markedly elevated TPO antibodies left this etiology more remote. Therefore, we suspected Graves' disease as an etiology; however, thyroid histopathology and ultrasound did not show compatible findings. Therefore, we suspect that the main etiology of thyrotoxicosis in the patient was the destruction of the thyroid follicles caused by a rapid invasion of malignant cells, which is responsible for the consequent release of preformed thyroid hormone. ATC is a rare endocrine neoplasm with high mortality; it may be associated with thyrotoxicosis, whose etiology can be varied; therefore, differential diagnosis is important for proper management.

Learning points: Anaplastic thyroid cancer is the thyroid cancer with the worst prognosis and the highest mortality. The association of anaplastic thyroid cancer with thyrotoxicosis is rare, and a differential diagnosis is necessary to provide adequate treatment. Due to the current pandemic, in patients with thyrotoxicosis, it is important to rule out SARS-CoV-2 as an etiology. Anaplastic thyroid cancer, due to its aggressive behavior and rapid growth, can destroy thyroid follicular cells, generating preformed thyroid hormone release, being responsible for thyrotoxicosis.

Figure 1

Cytological findings of thyroid core needle biopsy. In image (A), hematoxylin–eosin staining of two totally different areas of the same organ is observed: on the right side, normal thyroid tissue, and on the left side, loss of integrity of the thyroid morphology compatible with neoplastic tissue. Image (B) shows the proliferation of epithelioid cells, irregular organization, nucleus, and pleomorphic cytoplasms. Immunohistochemistry was positive for cytokeratin 7 (C) and weakly positive for thyroglobulin (D). All these findings confirm the diagnosis of anaplastic thyroid cancer.

Figure 2

Ectoscopy of the neck region. Size of the thyroid gland increases and erythema over the skin, attributable to cervical cellulitis.

Figure 3

Neck CT scan with contrast. In the sagittal plane (A) and axial plane (B), an irregular and heterogeneous mass measuring 76 × 68 × 58 mm is observed (black arrow), with thick calcifications, alteration of the adjacent fat planes, and areas of central necrosis in the right thyroid lobe, extending to the mediastinum.

Figure 4

CT scan of the chest with contrast. In the mediastinal window (A), mediastinal lymphadenopathies and thrombosis of the superior vena cava (white arrow) are observed. In the pulmonary window (B), multiple and bilateral irregular nodules of random distribution are observed, some cavities (the largest of 20 mm) findings suggestive of malignancy; likewise, ground-glass opacity is identified in both lungs.