Follicular lymphoma of the thyroid and the role of core needle biopsy.

Primary thyroid lymphoma (PTL) is a rare malignancy, accounting for less than 5% of thyroid neoplasms. PTL should be suspected when a patient presents with a rapidly enlarging goitre, especially in the setting of Hashimoto's thyroiditis. Fine-needle aspiration has a limited capacity for PTL diagnosis due to similar cytomorphological features of lymphoma with thyroiditis. Therefore, in case of clinical suspicion and if fine needle aspiration fails to diagnose PTL, a tissue biopsy should be performed. Treatment is dependent on both the stage and histology of PTL. Chemotherapy and local radiotherapy remain the mainstay treatment for PTL.