**4. Clinical features**

The majority of the patients present with a rapidly progressing neck mass with complaints of dysphagia, dyspnea, and neck pain. Approximately 90% will have regional or distant spread at the time of diagnosis [17–19]. The regional spread shows infiltration of perithyroidal fat, lymph nodes, trachea, esophagus, great vessels of the neck, and mediastinum. Based on the infiltration of adjacent neck structures, patients can also develop hoarseness (recurrent laryngeal nerve invasion), Horner's syndrome (parasympathetic chain involvement), and thromboembolic episodes due to carotid infiltration.

Around 40% of patients present with cervical lymphadenopathy and 43% will have distant metastasis most commonly involving lungs followed by bone and brain [20].

Also, patients can present with constitutional symptoms, such as pyrexia of unknown origin, anorexia, weight loss, and rarely with features of thyroiditis [22, 23].

On examination, there will be bilateral but asymmetric enlargement of the thyroid gland with ill-defined borders. Usually, they are nodular, woody hard in consistency, and may be tender. Some nodules may be fluctuant due to focal tumor necrosis [24]. Due to adhesion with the adjacent structures, most of the time the swelling does not move with swallowing. The skin over the swelling may be erythematous and ulcerated.

During clinical examination, they should undergo an ENT evaluation to rule out vocal cord dysfunction or airway compromise.

Other findings include dilated chest wall veins due to superior vena cava obstruction (SVCO) from a retrosternal thyroid growth, stridor due to tracheal invasion, and vocal cord paralysis.
