Abstract
OBJECTIVE: To determine the histopathologic features associated with ultrasonographic echogenicity of thyroid nodules. MATERIALS AND METHODS: This study included 95 nodules of 95 patients (76 women, 19 men; mean age 47.5 ± 12.9 years) with homogeneous echogenicity in which core needle biopsy was performed during a one year period. The nodule echogenicity was categorized into 4 grades (hyperechogenicity, isoechogenicity, mild hypoechogenicity, and marked hypoechogenicity). The biopsy specimens were evaluated by a pathologist regarding the histopathologic features of fibrosis, lymphoid infiltration, microfollicular pattern, uniform follicular pattern, and hypercellularity in nodules. We evaluated the association of each histopathologic feature among 3 categories of nodule echogenicity by multinomial regression analysis. RESULTS: The nodule echogenicity was isoechoic in 28 (29.5%), mildly hypoechoic in 37 (38.9%), and markedly hypoechoic in 30 (31.6%), and there was no hyperechoic nodule. There was a trend of increasing frequency of fibrosis (> 30%) as nodule echogenicity decreased (isoechogenicity, 10.7%; mild hypoechogenicity, 32.4%; and marked hypoechogenicity, 80%; p < 0.001). The microfollicular pattern, uniform follicular pattern, and hypercellularity were frequently found in mildly hypoechoic nodules than in isoechoic nodules (p ≤ 0.018). The fibrosis (> 30%) and hypercellularity were independently associated with mild or marked hypoechogenicity as compared to isoechogenicity (fibrosis; p ≤ 0.004 and hypercellularity; p ≤ 0.036), and only fibrosis (> 30%) was independently associated with marked hypoechogenicity as compared to mild hypoechogenicity (p = 0.004). CONCLUSION: The fibrosis (> 30%) and high cellularity are independently associated with mild or marked hypoechogenicity of nodules. The knowledge of the relationship of echogenicity and histopathology of thyroid nodules could improve management of patients with thyroid nodules.