A fascinating case of ectopic thyroid with Hashimoto’s thyroiditis

Hashimoto’s thyroiditis (HT) involving ectopic thyroid tissue (ETT) is an infrequent entity. A 34-year-old lady presented to the Department of Endocrinology with progressive neck swelling. She had undergone total thyroidectomy 8 years ago. She was initiated on levothyroxine after the surgery, which was subsequently discontinued by herself. On examination, a nodular swelling over the anterior aspect of the neck in the midline was present. Ultrasonography of the thyroid demonstrated a hypoechoic nodule measuring 3 cm × 1.4 cm with significant internal vascularity in the anterior aspect of the neck in the midline and right paramedian location, positioned superior to the thyroid cartilage. The thyroid bed was devoid of any thyroid tissue. Fine-needle aspiration cytology of the midline nodule in the neck demonstrated a polymorphous lymphocytic impingement and Hurthle cell changes in the lymphoid background, features consistent with HT (Bethesda category 2). As the thyroid stimulating hormone (TSH) was elevated (24.98 mIU/L), thyroxine replacement of 75 mcg was re-initiated for the patient at our center and later titrated to 100 mcg based on her rising TSH levels on subsequent follow-up. On titration of 100 mcg, she had TSH 0.005 mIU/L and T4 of 11.30 mcg/dL after 6 months. Subsequently, she had normalized TSH (0.496 mIU/L) with 88 mcg of levothyroxine. Even in the absence of the thyroid gland, thyroiditis can still occur in ETT, which may lead to confusing thyroid function test results. Strict compliance with thyroxine therapy will prevent further enlargement of the ectopically located thyroid in this scenario and will prevent the need for thyroidectomy.