In this retrospective study we analyzed cancer characteristics and outcome in a consecutive series of 48 young patients (< or =20 yr of age) with a differentiated thyroid cancer (DTC), observed during the period 1977-1998. In none of them was thyroid cancer related to ionizing radiation. The median age was 18.1 yr, range 7-20, and the female/male ratio was 2.5/1. Papillary thyroid cancer (PTC) occurred in 83% and follicular thyroid cancer (FTC) in 17% of cases. All patients underwent total or near total thyroidectomy plus pre- and/or paratracheal lymphnode dissection. Surgery complication rate was low (4% permanent hypoparathyroidism; no permanent lesion of recurrent laryngeal nerve). Extrathyroid disease was present in 52% of patients with PTC and in 50% of patients with FTC, while nodal metastases were present in 62.5% of patients with PTC and in 12.5% of patients with FTC. Lung metastases occurred in 10 patients with PTC (25%) and in none with FTC. Twenty-one patients required radioiodine treatment for metastatic disease: 11 patients for relapsing lymph-node metastases, 4 patients for lung metastases, 6 patients for both lymph-node and lung metastases. After a mean follow-up of 85+/-12 months all patients followed regularly (no.=47) were alive; 37 patients (79%) were free of disease and 10 (21%) had residual disease. Our results indicate that non-radiation-related DTC occurring in young patients often presents at an advanced stage. For this reason, although the prognosis is usually good in these patients, we believe that total or near total thyroidectomy with lymphadenectomy is always the required initial surgical treatment.