OBJECTIVE: Currently, little is known about the prevalence of thyroid tumors in multiple endocrine neoplasia type 1 (MEN1) patients and it is unclear whether tumorigenesis of these thyroid tumors is MEN1-related. The aim of the study was to assess the prevalence of thyroid incidentalomas in MEN1 patients compared with nonMEN1 patients and to verify whether thyroid tumorigenesis is MEN1-related. DESIGN: A cross-sectional study. METHODS: The study included two groups: patients with MEN1 and a matched non-MEN1 control group without known thyroid disease, who underwent an ultrasound of the neck for the localization of parathyroid adenoma. Ninety-five MEN1 patients underwent ultrasound of the neck and were matched on gender and age with non-MEN1 patients. The prevalence of thyroid incidentalomas described in the ultrasound report was scored. Multinodular goiters, solitary nodes, and cysts were scored as incidentalomas. Presence of nuclear menin expression was evaluated by menin immunostaining of the thyroid tumors. RESULTS: In the MEN1 group, 43 (45%) patients had a thyroid incidentaloma compared with 48 (51%) in the non-MEN1 group, of which 14 (15%) and 16 (17%), respectively, were solitary nodes. Menin was expressed in the nuclei of all evaluated thyroid tumors. CONCLUSIONS: MEN1 patients do not have a higher prevalence of thyroid incidentalomas compared with primary hyperparathyroidism patients without the diagnosis of MEN1. Menin was expressed in the thyroid tumors of MEN1 patients.