Differential diagnosis ; focal lymphocytic thyroiditis ; papillary thyroid cancer
Abstract
Purpose: It is often difficult to discriminate focal lymphocytic thyroiditis (FLT) or adenomatous hyperplasia (AH) from thyroid
cancer if they both have suspicious ultrasound (US) findings. We aimed to make a predictive model of FLT from papillary thyroid
cancer (PTC) in suspicious nodules with benign cytologic results.
Materials and Methods: We evaluated 214 patients who had undergone fine-needle aspiration biopsy (FNAB) and had shown
thyroid nodules with suspicious US features. PTC was confirmed by surgical pathology. FLT and AH were confirmed through
more than two separate FNABs. Clinical and biochemical findings, as well as US features, were evaluated.
Results: Of 214 patients, 100 patients were diagnosed with PTC, 55 patients with FLT, and 59 patients with AH. The proportion of
elevated thyrotropin (TSH) levels (p=0.014) and thyroglobulin antibody (Tg-Ab) or thyroid peroxidase antibody (TPO-Ab) positivity
(p<0.001) in the FLT group was significantly higher than that in the PTC group. Regarding US features, absence of calcification
(p=0.006) and “diffuse thyroid disease” (DTD) pattern on US (p<0.001) were frequently seen in the FLT group. On multivariate
analysis, Tg-Ab positivity, presence of a DTD pattern on US, and absence of calcification in nodules were associated with FLT with
the best specificity of 99% and positive predictive value of 96%. In contrast, a taller than wide shape of nodules was the only variable
significant for differentiating AH from PTC.
Conclusion: Suspicious thyroid nodules with cytologic benign results could be followed up with US rather than repeat FNAB, if
patients exhibit Tg-Ab positivity, no calcifications in nodules, and a DTD pattern on US.