Prevalence and risk factors for thyroid cancer in patients with multinodular goitre

Background Rates of thyroid cancer in patients with multinodular goitre (MNG) vary widely, from 3 per cent in older studies to 35 per cent in more recent studies. The purpose of the present study was to evaluate the prevalence of thyroid cancer in patients operated on for MNG, and to determine risk factors for incidental thyroid malignancy. Methods A prospectively developed database of all patients who underwent thyroidectomy for a benign MNG at the high-volume endocrine surgery unit of a tertiary referral university hospital was interrogated. Results A total of 3233 patients were analysed, separated into three groups according to their functional thyroid status (hypothyroid, hyperthyroid or euthyroid). There were 2788 women (86.2 per cent); the mean patient age was 56.4 years and mean preoperative disease duration was 106.2 months. Incidental thyroid cancer was identified in 1026 patients (31.7 per cent), of which 917 (89.4 per cent) were papillary cancers. Multivariable regression analysis identified functional thyroid status, younger age, male sex, smaller adenoma size, smaller thyroid glands, Hashimoto's thyroiditis and chronic non-specific thyroiditis as independent risk factors for thyroid cancer. Conclusion MNG was associated with a considerable rate of incidental thyroid cancer, which has been underestimated. A variety of factors should be taken into account when considering the malignant potential of a presumed benign MNG. A wide distribution of thyroid cancer rates has been demonstrated within a multinodular goitre. This study evaluated the incidence of and risk factors for thyroid cancer in patients operated on for benign multinodular goitre.