ABSTRACT
Background: Thyroid nodules are common and associated to a low risk of malignancy. Their clinical assessment usually includes a fine neddle aspiration biopsy (FNAB). Aim To identify ultrasonographic characteristics associated to papillary thyroid carcinoma (PTC) and generate a score that predicts the risk of PTC. Material and methods: Retrospective review of all fine needle aspiration biopsies of the thyroid performed in a lapse of two years. Biopsies that were conclusive for PTC were selected and compared with an equal amount of randomly selected biopsies that disclosed a benign diagnosis. Results: One hundred twenty two biopsies of a total of 1,498 were conclusive for PTC. Univariate analysis showed associations with PTC for the presence of micro-calcifications (Odds ratio (OR) 49.2: 95 percent confidence intervals (CI) 18.7-140.9), solid predominance (OR 25.1; 95 percent CI 6-220), hypoechogenicity (OR 23.5, 95 percent CI 6.5-122.6), irregular borders (OR 17, 95 percent CI 7.2-42.9), lymph node involvement (OR 12.3, 95 percent CI2.7-112), central vascularization (OR 12.2, 95 percent CI 4.8-33.3), local invasion and hyperechogenicity (OR 0.2; CI95 percent CI 0.03-0.6). Multivariate analysis disclosed microcalcifications (OR 28.1; CI 95 percent 8.9-89), hypoechogenicity (OR 9.4; 95 percent CI 1.5-59.5) and irregular borders (OR 4.7; CI 95 percent 1.5-15) as the variables independently associated with the presence of PTC. The prevalence of PTC in the presence of the three variables was 97.6 percent (Likelihood ratio (LR) 45) and 5.4 percent in their absence (LR 0.06). Conclusions: This scale predicts the presence or absence of PTC using simple ultrasound characteristics.