Thyroid Cytology Reporting and Diagnostic Accuracy: A Departmental Audit of the RCPath Guidelines

In the past there has been considerable variation in the way thyroid cytology was reported by pathologists. As the need for improving patient care increased to include more conservative surgical procedures for the management of thyroid lesions, there was a need for a standardized reporting format. This had to be reproducible and universal so that the implications of the reporting categories were clear to all pathologists, surgeons or clinicians. In 2009, The Royal College of Pathologists (RCPath) published ‘Guidance on Reporting of Thyroid Cytology Specimens’ and this guidance has been revised in 2016 [1]. This document details the standardized format for reporting Thyroid FNAC used in the UK today. The classification of thyroid cytology into ‘Thy categories’ is similar to the Bethesda system used in the USA in that it stratifies thyroid FNA’s into various disease categories. The UK system uses five main categories ranging from Thy 1Thy5 and certain categories are further subdivided into give additional diagnostic information. The Bethesda system uses six categories each with a percentage risk of malignancy. Currently there is little national data available on the percentage of cases that fall into each Thy category. Hence the positive predictive value (PPV) for each Thy category suggested in the RCPath guidance although rudimentary.