Context: Although advances in treatment have permitted patients with systemic lupus erythematosus (SLE) to live longer, the rates of several types of cancers in these patients appear to be increasing.

Objective: We used a prospective study to investigate the prevalence and features of thyroid cancer in SLE patients.

Design and Patients: The prevalence of thyroid cancer in 153 unselected SLE patients was compared with that in two population-based, gender- and age-matched control groups: 1) 459 subjects from an iodine-deficient area (iodine-deficient control) and 2) 459 subjects from an iodine-sufficient area (iodine-sufficient control). Thyroid function was assessed by measuring circulating thyroid hormones and autoantibodies, thyroid ultrasonography, and where necessary, fine-needle aspiration cytology.

Main Outcome and Results: The levels of circulating TSH, and anti-thyroglobulin and anti-thyroperoxidase antibodies were significantly higher in SLE patients (P < 0.001 for all). In addition, patients with SLE also exhibited a higher prevalence of hypothyroidism (P < 0.001). Five cases of papillary thyroid cancer were detected among SLE patients, whereas no cases were observed among iodine-deficient controls (P = 0.001), and only one case was observed among iodine-sufficient controls (P = 0.001). Among SLE patients with confirmed thyroid cancer, 80% showed evidence of thyroid autoimmunity, whereas only 31% of SLE patients without thyroid cancer exhibited evidence of thyroid autoimmunity (P = 0.02).

Conclusions: These data suggest that the prevalence of papillary thyroid cancer in SLE patients is higher than in age-matched controls, particularly in patients with thyroid autoimmunity. Consequently, careful thyroid surveillance is recommended during the follow-up of these patients.