Tuberculosis of the thyroid gland may present in two forms. The more common presentation is miliary spread to the thyroid gland as part of generalized dissemination. The less common form is focal caseous tuberculosis of the gland, which may present with localized swelling mimicking carcinoma, a cold abscess formation or as euthyroid nodular goiter. It may also manifest as subacute thyroiditis, or very rarely, as an acute abscess.
The signs and symptoms of thyroid TB are variable, and are most commonly associated with enlargement of the gland. Thyroid dysfunction is rare, but both hyperthyroidism and hypothyroidism have been reported.
Seed described 3 prerequisite conditions to be present for the diagnosis of thyroid tuberculosis: the demonstration of acid fast bacilli within the thyroid, a necrotic or abscessed gland, and a definiite tuberculous focus outside the thyroid.
Histologic and bacteriologic confirmation are adequate to make the diagnosis, so that fulfillment of the third criterion is not essential. Characteristic histologic findings include epithelioid cell granulomas with, peripheral lymphocytic infiltration, and Langerhans giant cells. The demonstration of central caseation necrosis is a cytologic finding that is specific to tuberculosis. Other diagnostic tests include chest X-ray, sputum analysis, mycobacterial cultures and MTB-PCR. However in some literature, AFB and culture analysis may not show tuberculosis and PCR can confirm TB in only 55% of the cases.
In this case, there were no signs and symptoms suggestive of other foci of TB in the body. The demonstration of epithelial cell granulomas with Langerhans giant cells and central caseation necrosis on histopathologic examination made the diagnosis of thyroid tuberculosis.
Antituberculous drugs remain the mainstay of treatment. Surgery may be indicated in the cases of acute abscess formation to avoid total destruction of the thyroid gland. Surgery may also be indicated to establish definite diagnosis when pre-operative workups are ambiguous.
Although seldom observed, tuberculosis should also be considered in the differential diagnosis of nodular lesions of the thyroid, particularly in communities with high TB prevalence. Ultrasound-guided FNAB is a useful diagnostic tool in the work-up of neck masses. In our case, confirmation of the diagnosis of TB of the thyroid was made by histopathologic examination. Treatment was mainly based on ATT. Surgical drainage and eventual thyroidectomy was deemed necessary due to the size of the abscess and establishment of the definitive diagnosis.