The 5th edition of WHO classification of tumors of endocrine organs: changes in the diagnosis of follicular-derived thyroid carcinoma

The 5(th) edition of the World Health Organization (WHO) classification of endocrine tumors was released in 2022. Several novelties have been introduced concerning the nomenclature and histopathological diagnosis of follicular-derived thyroid neoplasms. Tumor types have been sharply classified according to prognostic risk categories into benign tumors, low-risk neoplasms and malignant neoplasms. A grading system for differentiated thyroid carcinomas has been implemented with the aim of improving the stratification of tumors. Particular attention has been paid to the molecular profile of well-differentiated histotypes. In this review, the main changes introduced by the latest edition of the WHO system are presented. The practical effects on the diagnostic pathology of thyroid tumors, along with the clinical implications expected with the new classification scheme, are critically discussed.

Automated summary

The 5th edition of the WHO classification of endocrine tumors, released in 2022, introduces several novelties in the nomenclature and histopathological diagnosis of follicular-derived thyroid neoplasms. Tumor types are now categorized into benign tumors, low-risk neoplasms, and malignant neoplasms based on prognostic risk. A grading system for differentiated thyroid carcinomas has been implemented for better tumor stratification. The review critically discusses the practical effects on diagnostic pathology and the expected clinical implications of the new classification scheme.