Thyroid lymphoma

Primary thyroidal non-Hodgkin's lymphoma, albeit rare, is an important component of the differential diagnosis for thyroid nodules or malignancy, mainly because of the different prognosis and treatment approach (1,2). Only about 2% of extranodal lymphomas arise as primary malignancies within the thyroid gland and represent no more than 5% of all thyroid malignancies (3). In a Danish epidemiological survey, the annual incidence rate was estimated as 2.1 per million people, with a 4:1 female predominance (4). Most other retrospective series have confirmed this markedly higher frequency of disease in women (5-9). The mean and median ages at diagnosis are between 65 and 75 yr, suggesting that women present at a significantly older age than men (4-9); like anaplastic carcinoma, presentation before age 40 is extremely rare.