Approach to thyroid cytology: rationale for standardisation

Standardisation of thyroid cytology terminology and practice: are modifications necessary?-a narrative review

Universally accepted guidelines for diagnosis and management of any disease are desirable. Standardization of thyroid cytology reporting is aimed at guiding and improving clinical decision-making and management. However, socio-economic, and local factors and differences in disease prevalence and patterns require modification to suit local settings. 'One size fit all' approach is not possible for any disease diagnosis or management. The same concept is applicable in diagnosis and management of thyroid nodules. An additional special issue is the well-known high inter and intra-observer variability in the histological and cytological diagnosis of thyroid neoplasms. Despite this, thyroid cytology has a very significant influence in the management of thyroid diseases. An approach based on common principals with appropriate modifications that suits countries or continents is desirable and sustainable. The principals of TBSRTC have served as a framework for similar tiered classifications for reporting thyroid cytopathology. This article discusses globally available professional guidelines based on a common framework with appropriate modifications, with the universal aim of risk stratification of thyroid nodules.

The Japanese reporting system for thyroid aspiration cytology 2019 (JRSTAC2019)

We introduce the Japanese reporting system for thyroid aspiration cytology 2019 (JRSTAC2019) proposed by the Japan Association of Endocrine Surgery and the Japanese Society of Thyroid Pathology. Pathological classification and recommended clinical management for thyroid nodules in Japan are different from those described in the World Health Organization classification or the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC). Therefore, it was necessary to develop a reporting system adapted for Japan. JRSTAC2019 is a modified version of TBSRTC. Currently, JRSTAC2019 is widely used in Japan, although the details of the system have not been introduced in English. JRSTAC2019 comprises seven categories: (I) unsatisfactory, (II) cyst fluid, (III) benign, (IV) undetermined significance, (V) follicular neoplasm (FN), (VI) suspicious for malignancy (SFM), and (VII) malignant. "Cyst fluid" nodules are classified as an independent category, and "recommended management" is in the same category as "benign" nodules. Surgical resection for FN nodules is decided upon by considering several parameters, and the decision is made without performing gene analysis. Non-invasive follicular thyroid neoplasm with papillary-like nuclear features tends to be more often diagnosed as papillary carcinoma. The risk of malignancy of SFM in Japan is higher than that in Western countries, and resection rates of SFM and malignant tumors are lower owing to active surveillance for low-risk papillary microcarcinoma. We recommend that each country should develop its reporting system, suitable for its medical and social needs. However, it should be easily compatible with TBSRTC for the ease of academic data sharing.