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

ABSTRACT

INTRODUCTION: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.