Purpose: This study was performed to investigate the incidence and malignancy risk of thyroid nodules with isolated macrocalcification.
Methods: The isolated macrocalcification was defined as an entirely calcified nodule without any identified solid component on US, in which the assessment of other US characteristics was impossible owing to dense posterior shadowing. From January 2011 to June 2018, a total of 3061 consecutive patients with 3852 thyroid nodules (≥ 1 cm) underwent ultrasonography (US)-guided fine-needle aspiration (FNA). We retrospectively reviewed all US images of those nodules to determine nodules with isolated macrocalcifications. We assessed the incidence, malignancy rate, and the size distribution of thyroid nodules with isolated macrocalcifications. The nodule size was categorized as 3 groups (group 1: 1~1.4 cm, group 2: 1.5~1.9 cm, group 3: ≥ 2 cm).
Results: Isolated macrocalcification was found in 38 (1.2%) of 3061 patients. Among 38 nodules with isolated macrocalcifications, the final diagnosis was achieved in 30 nodules and seven malignant tumors (6 conventional type and 1 follicular variant type papillary carcinomas) were diagnosed by surgery (n=6) and FNA (n=1). The malignancy rate of isolated macrocalcification was 23.3% in 30 nodules with final diagnoses and 18.4% in all nodules. The size of isolated macrocalcifications was group 1 (n=27, 71.1%), group 2 (n=8, 21%), and group 3 (n=3, 7.9%). The mean size of malignant tumors was 1.5 ± 0.4 mm and the tumor size was group 1 (n=3, 43%), group 2 (n=3, 43%), and group 3 (n=1, 14%). Among 6 malignant tumors with surgical pathology diagnoses, the extrathyroidal extension was found in 4 (66.7%) and lymph node metastasis in 2 (33.3%) tumors.
Conclusion: Thyroid nodule with isolated macrocalcification (≥ 1 cm) was found in 1.2% of our cohort patients and showed an intermediate malignancy risk (at least 18.4%).