Prevalence and distribution of carcinoma in patients with solitary and multiple thyroid nodules on sonography.

CONTEXT: Controversy remains as to the optimal management of patients with multiple thyroid nodules.

OBJECTIVE: The objective of this study was to determine the prevalence, distribution, and sonographic features of thyroid cancer in patients with solitary and multiple thyroid nodules.

DESIGN: We describe a retrospective observational cohort study that was carried out from 1995 to 2003.

SETTING: The study was conducted in a tertiary care hospital.

PATIENTS: Patients with one or more thyroid nodules larger than 10 mm in diameter who had ultrasound-guided fine needle aspiration (FNA) were included in the study.

MAIN OUTCOME MEASURES: The main outcome measures were prevalence and distribution of thyroid cancer and the predictive value of demographic and sonographic features.

RESULTS: A total of 1985 patients underwent FNA of 3483 nodules. The prevalence of thyroid cancer was similar between patients with a solitary nodule (175 of 1181 patients, 14.8%) and patients with multiple nodules (120 of 804, 14.9%) (P = 0.95, chi(2)). A solitary nodule had a higher likelihood of malignancy than a nonsolitary nodule (P < 0.01). In patients with multiple nodules larger than 10 mm, cancer was multifocal in 46%, and 72% of cancers occurred in the largest nodule. Multiple logistic regression analysis of statistically significant features demonstrates that the combination of patient gender (P < 0.02), whether a nodule is solitary vs. one of multiple (P < 0.002), nodule composition (P < 0.01), and presence of calcifications (P < 0.001) can be used to assign risk of cancer to each individual nodule. Risk ranges from a 48% likelihood of malignancy in a solitary solid nodule with punctate calcifications in a man to less than 3% in a noncalcified predominantly cystic nodule in a woman.

CONCLUSIONS: In a patient with one or more thyroid nodules larger than 10 mm in diameter, the likelihood of thyroid cancer per patient is independent of the number of nodules, whereas the likelihood per nodule decreases as the number of nodules increases. For exclusion of cancer in a thyroid with multiple nodules larger than 10 mm, up to four nodules should be considered for FNA. Sonographic characteristics can be used to prioritize nodules for FNA based on their individual risk of cancer.