ESPE Abstracts

Background: DICER1 syndrome is caused by germline mutations in the DICER1 gene. It is associated with a wide spectrum of benign and malignant neoplasms, which are accompanied by specific somatic mutations in DICER1. Multinodular goiter (MNG) is a common clinical feature of DICER1 syndrome in children and adults; the thyroid ultrasound (US) features of MNG in the setting of DICER1 syndrome have not been widely reported.

Objective: The aim of this study is to determine the US characteristics of MNG in patients with DICER1 syndrome.

Materials and Methods: This retrospective study evaluated thyroid ultrasound studies performed between 2011 and 2018 at a single centre. Patients ≤18 years with DICER1 germline mutations and an intact thyroid gland were identified and included. Mutation-positive parents without previous thyroidectomy were also included. All studies were performed by the same pediatric endocrinologist and were subsequently re-examined by an independent radiologist from another academic center. The architecture of lesions was characterized as: simple cyst, septated cyst, mixed cystic and solid, or solid. US phenotypes of MNG in the setting of DICER1 mutations were compared with known US features of thyroid malignancy. All mutations in DICER1 were identified in a single research laboratory and confirmed via orthogonal techniques.

Results: Thirteen DICER1 mutation-positive persons were identified (10 children, 3 adults). Three children had a normal thyroid ultrasound; therefore, thyroid abnormalities were assessed in 7 children and 3 adults. In both children and adults, mixed cystic and solid nodules predominated. We did, however, observe also single cystic, single cystic septated and single solid nodules. Solid lesions were present in 9 of 10 patients but all were isoechogenic and without detectable intranodular blood flow except in one patient with multiple solid nodules. Other findings that are characteristic for MNG in DICER1 syndrome were as follows: multiple lesions (≥3) in all examined patients ocasionally with a "spoke-like" presentation, absent vascular flow on Power/Color Doppler (except 1 patient), and macrocalcifications were present in all three adults.

Conclusions: The spectrum of US findings of MNG in DICER1 mutation-positive patients is characteristic and is largely distinct from typical features of thyroid malignancy. Observed patterns include: multiple lesions (≥3), mixed cystic and solid elements, absence of detectible vascular flow, and a "spoke-like" appearance. Macrocalcification was observed only in adults. These features should sensitize physicians performing thyroid ultrasound to the possible presence of underlying DICER1 syndrome.