Background: Thyroid nodules are common and associated to a low risk of malignancy. Their clinical assessment usually includes a fine needle 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% confidence intervals (CI) 18.7-140.9), solid predominance (OR 25.1; 95% CI 6-220), hypoechogenicity (OR 23.5, 95% CI 6.5-122.6), irregular borders (OR 17, 95% CI 7.2-42.9), lymph node involvement (OR 12.3, 95% CI2.7-112), central vascularization (OR 12.2, 95% CI 4.8-33.3), local invasion and hyperechogenicity (OR 0.2; CI 95% CI 0.03-0.6). Multivariate analysis disclosed microcalcifications (OR 28.1; CI 95% 8.9-89), hypoechogenicity (OR 9.4; 95% CI 1.5-59.5) and irregular borders (OR 4.7; CI 95% 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% (Likelihood ratio (LR) 45) and 5.4% in their absence (LR 0.06).
Conclusions: This scale predicts the presence or absence of PTC using simple ultrasound characteristics.