What is Thy3a? A study of 336 Thy3a (AUS/FLUS) thyroid FNAs with histology compares UK RCPath with other reporting systems and shows how Thy3a subclassification can improve risk stratification and help address overuse of this category.

INTRODUCTION: Thy3a (AUS/FLUS) is an indeterminate and heterogeneous category in thyroid cytology. Thy3a reporting rates vary widely, with many laboratories documenting overuse. Subclassification of Thy3a helps with risk stratification. We aimed to investigate whether subclassification can also help address Thy3a overuse. We compare the UK reporting system with other terminologies. METHODS: An audit of thyroid fine needle aspirations (FNAs) reported at our institution between 2012 and 2017 was performed. Thy3a FNAs followed by histology were reviewed and subcategorised into four subgroups: Scanty Atypia (SA), Scanty Microfollicular (SMF), Favour Benign (FB) and Thyroiditis versus Neoplasm (TVN). Review and subclassification were blinded to histology outcomes. FNAs were correlated with histology and statistical analysis was performed. RESULTS: Our Thy3a rate was high (24% of all thyroid FNAs). For 336 Thy3a FNAs with histology, the malignancy rates of the four subgroups were: SA 68%, SMF 20%, FB 4%, TVN 31%. There were significant associations between subgroup and malignancy risk, and between subgroup and tumour risk. On histology, SA had more malignancies than expected and FB had fewer. SA and SMF had more tumours than expected and FB had fewer. SMF and Thy3f FNAs were similar in terms of tumour and malignancy outcomes. CONCLUSIONS: Subclassification of Thy3a FNAs into these four subgroups is recommended. This can improve risk stratification and help address overuse of Thy3a. We propose that some FB and SMF cases could be safely diverted to Thy2 and Thy3f respectively. We compare various reporting terminologies and question how indeterminate FNAs should be classified.

Cytological accuracy and radiological staging in patients with thyroid cancer in Glasgow.

To assess the accuracy of initial combined cytological accuracy and radiological staging of patients suspected of having thyroid malignancy with their final histopathology. Retrospective case series in a tertiary referral centre for head and neck malignancy. All patients with malignant thyroid cytology and cytology suspicious for malignancy, between the dates of June 2010 and July 2014, were included. The pre-operative staging was compared against the final histological staging. Demographics and outcomes for each patient were recorded. Sixty-five patients were recorded in this group. 20 (30.7 %) were male. The mean age at presentation was 51 years (SD 16.8 years). 39 (60 %) patients were aged over 45 years. Fine needle aspiration cytology (FNAC) was performed in all patients and was Thy 4 in 40 (62 %) and Thy 5 in 25 (38 %). Following surgery or subsequent biopsy, FNAC was found to be accurate in 38/40 (Thy 4) and 25/25 (Thy 5) cases in diagnosing malignancy, with Thy 4 yielding 95 % malignancy and Thy 5 % 100 %. Fifty-eight patients underwent a surgical procedure for thyroid cancer. Two further patients had a diagnostic hemi-thyroidectomy for later proven benign disease. Five patients due to medical co morbidities, inoperable disease or refusal of surgery were managed non-surgically. In the surgical group 16 patients underwent a diagnostic hemi-thyroidectomy and 11 of these required a completion thyroidectomy. Forty-six patients underwent total thyroidectomy. Forty-six patients underwent a neck dissection: 27 prophylactic central compartment neck dissections and 19 planned therapeutic neck dissections were performed. Radiological staging correctly predicted final pathological TNM staging in 25 (43 %) patients. 27 (47 %) patients had radiological staging which under staged their final histological staging and 6 (10 %) patients had scans that over staged their cancer. Of those that were under staged, 15 (56 %) had their nodal disease under staged (following prophylactic central neck dissection). Radiological staging comprised ultrasound (n = 58) and CT scanning (n = 45/58 pre-operatively). Pre-operative staging in thyroid cancer should include cytology, ultrasound and CT scanning. Unless low-risk papillary thyroid cancer is suspected pre-operatively, patients with Thy 4 cytology can be given the offer of a total thyroidectomy as surgical management.