WHO Classification of Thyroid Neoplasms 5th Edition (2022)

Rodrigo Arrangoiz MS, MD, FACS, FSSO
  • Key Structural Changes:
    • Tumors are now classified by cell of origin and malignant potential:
      • Benign
      • Low-risk
      • Malignant
    • Greater emphasis on:
      • Molecular alterations, histologic grading, and tumor behavior
    • Terminology changes:
      • “Variants” are now “subtypes”
      • “Hürthle cell” is replaced by “oncocytic
  • Classification Framework:
    • Tumors are grouped by:
      • Cell lineage
      • Pathologic behavior
      • Molecular profile
    • They have four hierarchical ranks:
      • Category → family → type → subtype 
  • Follicular cell–derived neoplasms are stratified into:
    • Benign tumors
    • Low‑risk neoplasms
    • Malignant neoplasms 
    • Other categories include:
      • C‑cell (medullary) tumors
      • Mixed tumors
      • Salivary gland–type carcinomas
      • Thymic tumors
      • Embryonal lesions
      • Tumors of uncertain histogenesis
  • Classification by Cell of Origin:
    • Follicular Cell-Derived Tumors:
      • Benign:
        • Follicular adenoma
        • Oncocytic adenoma:
          • Formerly “Hürthle cell adenoma
        • Papillary architecture adenoma
        • Follicular nodular disease:
          • New term replacing multinodular goiter
    • Low-Risk Neoplasms:
      • NIFTP:
        • Noninvasive Follicular Thyroid Neoplasm with Papillary-like Nuclear Features
      • Tumor of uncertain malignant potential
      • Hyalinizing trabecular tumor
    • Malignant:
      • Papillary thyroid carcinoma (PTC) – with subtypes:
        • Classical
        • Tall cell
        • Columnar cell
        • Solid
        • Diffuse sclerosing
        • Hobnail
      • Follicular thyroid carcinoma (FTC):
        • Minimally invasive
        • Widely invasive
      • Oncocytic carcinoma
      • Poorly differentiated thyroid carcinoma (PDTC)
      • Differentiated high-grade thyroid carcinoma (new)
      • Anaplastic thyroid carcinoma (ATC)
    • C Cell-Derived Tumors:
      • Medullary thyroid carcinoma (MTC):
        • New grading system based on mitotic count, necrosis, and Ki-67 index
      • Calcitonin-secreting hyperplasia (C-cell hyperplasia)
    • Mixed Tumors:
      • Mixed medullary and follicular carcinoma
    • Tumors of Uncertain Histogenesis:
      • Cribriform-morular thyroid carcinoma:
        • Formerly a subtype of PTC
    • Thyroblastoma (new entity)
    • Salivary Gland-Type Tumors of the Thyroid:
      • Mucoepidermoid carcinoma
      • Secretory carcinoma
    • Thymic-Origin Tumors:
      • SETTLE:
        • Spindle epithelial tumor with thymus-like differentiation
      • CASTLE:
        • Carcinoma showing thymus-like differentiation
  • Differentiated High-Grade Thyroid Carcinoma (DHGTC):
    • New category for tumors with high mitotic rate or necrosis:
      • But that retain differentiation (e.g., follicular or papillary histology)
  • NIFTP is formally recognized as a low-risk neoplasm, not carcinoma
  • References:
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Published by Rodrigo Arrangoiz MS, MD, FACS, FSSO

My name is Rodrigo Arrangoiz I am a breast surgeon/ thyroid surgeon / parathyroid surgeon / head and neck surgeon / surgical oncologist that works at Center for Advanced Surgical Oncology in Miami, Florida. I was trained as a surgeon at Michigan State University from (2005 to 2010) where I was a chief resident in 2010. My surgical oncology and head and neck training was performed at the Fox Chase Cancer Center in Philadelphia from 2010 to 2012. At the same time I underwent a masters in science (Clinical research for health professionals) at the University of Drexel. Through the International Federation of Head and Neck Societies / Memorial Sloan Kettering Cancer Center I performed a two year head and neck surgery and oncology / endocrine fellowship that ended in 2016. Mi nombre es Rodrigo Arrangoiz, soy cirujano oncólogo / cirujano de tumores de cabeza y cuello / cirujano endocrino que trabaja Center for Advanced Surgical Oncology en Miami, Florida. Fui entrenado como cirujano en Michigan State University (2005 a 2010 ) donde fui jefe de residentes en 2010. Mi formación en oncología quirúrgica y e n tumores de cabeza y cuello se realizó en el Fox Chase Cancer Center en Filadelfia de 2010 a 2012. Al mismo tiempo, me sometí a una maestría en ciencias (investigación clínica para profesionales de la salud) en la Universidad de Drexel. A través de la Federación Internacional de Sociedades de Cabeza y Cuello / Memorial Sloan Kettering Cancer Center realicé una sub especialidad en cirugía de cabeza y cuello / cirugia endocrina de dos años que terminó en 2016.

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