Are There Any Specific Ultrasound Findings of Nodular Hyperplasia (Leave Me Alone Lesion) to Differentiate It from Follicular Adenoma?

Background: Among benign thyroid nodules, nodular hyperplasia (NH) is the most common and represents a leave me alone lesion with no requirement for further treatment, while follicular adenoma (FA) is a lesion that should potentially be removed due to the difficulty of differentiation from a carcinoma on a biopsy alone. Purpose: To evaluate whether there are specific ultrasound (US) findings for an NH to distinguish it from an FA. Material and Methods: Pathologically proven cases of benign thyroid nodules (95 cases: 53 NH, 42 FA) were reviewed retrospectively. The number of associated nodules, the nodule size, internal content, shape, margin, echogenicity, presence of peripheral halo, and calcification were analyzed using grayscale ultrasonography. Results: NHs were predominantly solid in 40 cases (75.5%) and predominantly cystic in 13 cases (24.5%), while FAs were predominantly solid in all cases (n=42, 100%) (P0.001). A spongiform appearance was present exclusively in NH (9/53, 17.0%). For NH, 83.0% of the lesions (44/53) showed an isoechoic pattern. For FA, the lesions showed a variable echoic pattern, including a marked hypoechoic pattern (5/42, 11.9%), a hypoechoic pattern (22/42, 52.4%), and an isoechoic pattern (15/42, 35.7%) (P0.001). The nodule size, shape, margin, presence of peripheral halo, and calcification did not show any difference between FA and NH. Conclusion: The ratio of solid to cystic content, spongiform appearance, and echogenicity is a combination of US findings that may be helpful in distinguishing an NH from an FA, and may thereby help to avoid unnecessary fine-needle aspirations for leave me alone lesions.