Summary

A 30-year-old Filipino woman presented with goitre of 4 years’ duration. The right thyroid lobe was enlarged with no palpable lymph nodes. She had no thyrotoxic signs and symptoms.

Free thyroxine and thyrotropin were normal. Ultrasound revealed a cystic nodule on the right lobe. Fine needle aspiration biopsy was consistent with colloid nodule.

She underwent right lobectomy with extended isthmusectomy. Microscopic examination of the 6.5 cm mass showed well-defined, round, nests of tumour cells surrounded by a rim of collagen. Mitotic figures and necrosis were absent. There was capsular invasion. Immunohistochemical staining was positive for thyroglobulin and negative for calcitonin. These findings gave the diagnosis of insular thyroid carcinoma.

She underwent complete thyroidectomy with central node dissection. Five weeks after, she received 3700 MBq of radioactive iodine 131. Post-treatment, whole body scan revealed functioning thyroid tissue limited to the thyroid bed. The patient is on regular follow-up 2 years after diagnosis with no evidence of disease.