Diagnosis of Metastasis to the Thyroid Gland: Comparison of Core-Needle Biopsy and Fine-Needle Aspiration

Objectives Early detection and diagnosis of metastasis to the thyroid gland is important. This study aims to evaluate the clinical value of core-needle biopsy (CNB) by comparing the results of CNB and fine-needle aspiration (FNA) in patients with clinically suspected metastasis to the thyroid gland. Study Design Case series with chart review. Setting Tertiary referral practice. Subjects Fifty-two thyroid nodules from 52 patients with clinically suspected metastasis to the thyroid gland (mean age, 62.8 years). Methods Of these 52 patients, FNA was initially used in 41 patients and CNB in 20 patients (11 patients as the initial approach and 9 patients after inconclusive FNA results). Ultrasound features of metastasis to the thyroid gland were evaluated. The diagnostic performance, repeated diagnostic examination rate, and diagnostic surgery rate were evaluated for FNA and CNB. Results Among these 52 patients, 46 were diagnosed with thyroid metastases and 6 were diagnosed with primary thyroid cancer. Common ultrasound features were an ovoid to round shape (58.7%), ill-defined margin (56.5%), hypoechogenicity (65.2%), and no calcifications (87.0%). Core-needle biopsy achieved a significantly higher sensitivity than FNA (100.0% vs 58.6%, P = .008) without any false-negative results. Both the repeated diagnostic examination rate and the diagnostic surgery rate were significantly lower in CNB than in FNA (5.0% vs 46.3%, P = .001, and 5.0% vs 34.1%, P = .013, respectively). Conclusions In cases of known rare primary malignancy, nontypical ultrasound features of primary thyroid malignancy, and need for an additional immunohistochemical analysis, CNB may be primarily considered.