ODP481 Frequency and outcomes of reporting Bethesda class III thyroid cytopathology- An integrated health network's experience

Abstract

Abstract Introduction Indeterminate thyroid nodule cytologic diagnosis causes anxiety and confusion to the patient and typically results in additional intervention including thyroid surgery. This increases risk of harm and cost of healthcare. The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) recommends that cytologists attempt to limit reporting 'indeterminate' [Bethesda III (B-III)] category when interpreting thyroid fine needle aspiration (FNA) specimens, and that all effort be made to limit this diagnosis to less or equal to 7% of all thyroid FNA cases. B-III encompasses follicular lesion of undetermined significance (FLUS) and atypia of undetermined significance (AUS). Because we noted a high reporting of B-III cases at our institution, we aim to review the cytologic interpretation of thyroid FNAs, specifically, the rate of indeterminate cytologic diagnoses. Our second aim is to assess the outcomes of nodules labeled as B-III category. Methods We reviewed the electronic medical records of adults who underwent FNA of thyroid nodules at Allegheny Health Network between January 1, 2016 and December 31, 2019. Results 700 patient records were reviewed, out of which 167 records were excluded (non-thyroid FNA or no relevant records). Meaningful records were available for 725 thyroid nodules biopsied during the study period (533 patient records). Mean age in our sample was 54.7±13.9 years and female-to-male ratio was 4: 1. Percent reporting of diagnostic categories based on Bethesda system were as follows: non-diagnostic/unsatisfactory (B-I) 8%; benign (B-II) 52%; FLUS/AUS (B-III) 28%; FN/SFN (B-IV) 6.2%; suspicious for malignancy (B-V)2.3%; and malignant (B-VI) 3.2%. Out of 28% reported as B-III, 73% were FLUS and 27% were AUS. Results of molecular diagnostic testing (ThyGeNEXT-ThyraMIR; Interpace Diagnostics®) were available for 95/203 of B-III category cases, of which 76% were labeled as very likely benign (probability of malignancy ≤5%) and 15% had low to moderate (10-40%) probability of malignancy. Only 9/95 (9%) had a ≥ 45% probability of malignancy. Four cases out of the 9 above cases were confirmed malignant and 1 was 'indeterminate' on surgical pathology. One in four of all B-III category nodules (n=52) underwent partial or total thyroidectomy, of which 32 were reported as benign, 18 malignant, one NIFTP, and one indeterminate by final surgical pathology. Conclusion We observed higher than recommended (28%) rate of B-III thyroid cytology at our institution. Most of these nodules underwent further interventions (molecular testing and/or thyroidectomy) where the majority were determined to be benign. All efforts should be made to decrease this rate with the ultimate goal of improving patient care, decrease unnecessary intervention, and reduce healthcare cost. Presentation: No date and time listed