Malignant thyroid bed mass after total thyroidectomy.

Purpose: Ultrasonographic (US) criteria on malignant thyroid bed mass have been suggested, including taller than wide shape, loss of echogenic hilum, abnormal vascularity, and microcalcification. The relationship between fine-needle aspiration (FNA) cytology findings and US findings on thyroid bed mass is unknown. We have retrospectively assessed the malignant thyroid bed mass after total thyroidectomy due to papillary thyroid carcinoma (PTC).

Methods: We retrospectively evaluated 2,048 patients who underwent total thyroidectomy due to PTC. FNA was performed in 97 patients on the thyroid bed under US surveillance. The 97 suspicious thyroid bed masses were divided into two groups: metastatic thyroid bed group (n = 34) and nonmetastatic group (n = 63). The groups were evaluated according to various clinical, serologic, and US findings.

Results: Within a median 47.0 months of follow-up, the proportion of malignant thyroid bed mass was high in large tumor size (1.37 cm vs. 1.03 cm), isthmic position (10.3% vs. 3.9%), and previous N1a (55.9% vs. 34.9%). US findings revealed that the presence of microcalcification or macrocalcification (47.1% vs. 19.0%) and thyroid bed mass height (5.4 mm vs. 3.9 mm) were the only discriminable criteria for central compartment recurrence. But, degree of echogenicity, loss of hilum, and irregularity of margin failed to discriminate malignant thyroid bed mass.

Conclusion: US findings on malignant thyroid bed mass were different from previously reported general criteria on lateral metastatic nodes. Additional FNA cytology should be performed on patients, even low-risk patients, who present the above findings.