Incidental thyroid nodules on COVID-19-related thoracic tomography scans: a giant cohort

Computerized thoracic tomography (CT) imaging was extensively employed, especially in the early months of the COVID-19 pandemic. An incidental thyroid nodule (ITN) is defined as a nodule not previously detected or suspected clinically but identified via an imaging study. The present study aimed to determine the incidence of thyroid nodules incidentally detected in thoracic CTs for the suspicion of COVID-19 pneumonia.

Adult patients who underwent thoracic CT in our hospital for COVID-19 management were retrospectively identified between March 2020 and September 2020. Medical information registered in the hospital and national health system was reviewed. The prevalence of incidental thyroid nodules at CT, thyroid function test results of patients with incidental lesions, correlation of CT findings with ultrasonography (US) findings, and fine-needle aspiration biopsy (FNAB) results were evaluated.

We analyzed 35,113 patients who had COVID-19-indicated CT scans. There was information about the thyroid gland in CT reports of 3049 patients. The prevalence of ITN was 3.82% (1343/35,113 patients) and thyroid heterogeneity was 1.11% (388/35,113 patients). While it was explicitly stated that no pathology was found in the patient's thyroid gland in 3.75% of patients (1318/35,113), no information was given about the thyroid gland in 91.32% of the patients (32064/35,113). Thus, the number of patients informed about their thyroid was 3049 (8.68%) and the number of patients with thyroid pathology was 1731 (4.93%). It was observed that 308 of 1731 patients (17.80%) had follow-up thyroid US. An FNAB was indicated in 238 patients (87.50%). Of the 238 patients with indication for biopsy, only 115 (48.31%) underwent a thyroid FNAB. The cytological diagnosis was benign in 59 (51.30%), non-diagnostic in 30 (26.08%), atypia of uncertain significance in 22 (19.13%), and suspected follicular neoplasia/follicular neoplasia in four patients (3.46%). Thyroidectomy was performed in six more patients due to large nodules and the final diagnosis was benign in two and papillary thyroid cancer in three patients.

Increased use of thoracic CT during the COVID-19 pandemic probably enabled improved detection of ITNs. In this large-scale study, the prevalence of thyroid nodules reported with thoracic CT was 3.82%, while thyroid cancer was detected in 1.30% of patients evaluated with US. We recommend against using thoracic CT scans as a direct means of assessing thyroid disease owing to the low number of detected cancer cases in our cohort of 35,113 patients. However, thoracic CT scans obtained for various reasons might provide the opportunity for early diagnosis and treatment of thyroid disease, including cancers.