Special US pattern of thyroid lesions; “nodule within the nodule”

Purpose: The technical improvement of modern ultrasound (US) equipment allows a better evaluation of the sonographic structure of the thyroid and of the thyroid nodules (TN). The aim of this prospective study is an evaluation and presentation of a new US-pattern of the thyroid lesions denominated “nodule within the nodule”.

Methods: Thyroid US with 18 MHz transducer in 540 patients. In case of solid TN, the presence of additional circumscribed thyroid lesions within the nodule was studied. The uptake of such TN at thyroid scan with 99 m-Tc-Pertechnetate and/or the histology after surgery was evaluated.

Results: 1920 TN with diverse US pattern were detected. 24 lesions were slightly hypoechoic till isoechoic nodules (diameter between 15 – 35 mm) with hypoechoic halo and peripheral vascularization, which showed additional small nodules (diameter between 5 – 10 mm) within the TN, mainly hypoechoic nodules with microcysts and a peripheral perfusion of diverse degree. These 24 TN showed at the thyroid scan a normal uptake compared to the paranodular tissue or a hypercaptation.

Conclusion: The special US pattern of thyroid lesions called “nodule within the nodule” is seldom, but it should be known and be taken into consideration in every thyroid US in order to avoid erroneous reports or false US descriptions. The pattern “nodule within the nodule” corresponds to scintigraphic lesions with normal uptake or toxic thyroid adenomas.