Sonographic Diagnosis of Papillary Thyroid Carcinoma
Objective: To assess the value of ultrasonography (US) in reliably differentiating benign from malignant thyroid nodules, and in defining the malignant nature and the histotype of papillary thyroid carcinomas (PTC). Methods: A high-resolution real-time US system with a 7.5-MHz linear probe was used. The sonographic features of 39 histopathologically proven PTC cases were retrospectively reviewed and compared with the US features of 52 benign thyroid nodules (BTN). The US identification of PTC malignancy was based on the simultaneous presence of multiple US features seen exclusively in PTC and not in BTN. Results: Based on the simultaneous presence of exclusive malignant US features seen in PTC but not in BTN, identification of the malignant nature of PTC was certain in 74% of the cases and less certain in 8% of the cases. In a third group, 15% of the cases showed predominantly benign US features, while 1 patient (3%) was operated as a case of multinodular goiter and diagnosed histologically as having occult PTC. No malignant features were seen by US and it was not associated with metastasis. US identification of the histological type of PTC was based on the finding that a thyroid lesion presenting as a predominant cyst with a punctately calcified endoluminal projecting solid mural nodule was an exclusively specific feature of cystic primary PTC. Both, totally cystic and microcalcified predominantly cystic metastatic lymph nodes were also characteristically seen in metastatic PTC. Accordingly, the histotype of PTC was only identified in its cystic form, whether it was primary (13%) or metastatic (31%). Both constituted 44% of the 39 PTC cases. Conclusion: High-resolution real-time ultrasonography was found to be a useful first line diagnostic modality of PTC. It was reliable in differentiating benign from malignant thyroid nodules and in identifying the histotype of PTC in cases with cystic metastasis or where the primary or the metastatic nodule is cystic with microcalcified projecting solid mural nodule. Fine needle aspiration biopsy is to be resorted to, mainly in equivocal cases.