The largest CAP-certified Chinese reference laboratory experience with the Bethesda system for reporting thyroid cytopathology: correlation with histologic and BRAF data

Abstract

Thyroid fine needle aspiration biopsy (FNAB) has not been widely used in most areas of China. We investigated a large cohort of thyroid FNAB using the Bethesda system for reporting thyroid cytopathology (TBSRTC) from the largest College of American Pathology (CAP)-certified reference laboratory in China. Patients with thyroid FNAB between 2014 and 2016 from Guangzhou Kingmed Diagnostics were retrospectively retrieved and the histologic follow-up results and BRAF results were collected and analyzed. A total of 7355 thyroid FNAB cases were identified. The average age of these patients was 48.03 years (range: 5-90 years). A total of 875 cases (11.9%) were reported as nondiagnostic, 4041 (54.9%) cases were benign, 736 cases (10.0%) were atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS), 53 cases (0.7%) were suspicious for follicular neoplasm, 615 cases (8.4%) were suspicious for malignancy, and 1035 cases (14.1%) were positive for malignancy. Histologic follow-up was available on 552 patients. Among 13 cases of AUS/FLUS, 8 (61.5%) had malignancy on histology; 195 (92.0%) of the suspicious for malignancy cases had malignancies on histology, and 320 (98.5%) of the positive for malignancy cases had malignancies on histology. BRAF analysis was performed on 578 cases. Sixty cases with BRAF data had histologic follow-up, all 4 benign cases had negative BRAF, one follicular adenoma had negative BRAF, and 37 of the 55 PTC cases (67.3%) had positive BRAF. BRAF mutation has a 100% positive predictive value of malignancy for the indeterminate thyroid FNABs. This is the largest cohort of thyroid FNA reported using TBSRTC in China and the data are helpful for better understanding the status of thyroid FNA in China.