Microfilariae identified in FNA of a thyroid nodule.

A patient presented with hyperthyroidism and a thyroid swelling, clinically thought to be malignant. Fine-needle aspiration of the thyroid nodule revealed microfilariae of Wuchereria bancrofti. After therapy the thyroid swelling subsided and the patient became euthyroid. The possible etiologic role of microfilariae in the genesis of the thyroid tumor and hyperthyroidism is discussed.