Thyroid Cancer Staging: Historical Evolution and Analysis From Macrocarcinoma to Microcarcinoma

Abstract

The classification of thyroid cancer diagnosis and treatment has evolved dramatically since the Union for International Cancer Control (UICC) published the first staging system in 1968. A careful review of the eight published editions of well-differentiated thyroid cancer (WDTC) staging by the UICC and the American Joint Committee on Cancer (AJCC) was performed. Each edition was analyzed to clearly understand which development published and accepted by specialists treating thyroid cancer justified considering a new updated edition. This study presents a comprehensive review of the remarkable evolution of thyroid cancer staging, highlighting the various changes in several areas throughout the years and editions. There were surprising changes within the eight publications: the tumor size was progressively reduced from 4 cm in the first AJCC volume to less than 1 cm in the seventh and eighth UICC and AJCC editions, classifying these small, WDTCs known up to now as "microcarcinomas." Extrathyroidal extension was accepted after the third edition; this description certainly plays a key role in today's decisions to manage this tumor as a prognostic factor. The age specification of 45 years prevailed for seven consecutive publications until it was raised to 55 years in the eighth thyroid cancer staging system. Without a doubt, this iconic change allowed physicians around the world to give their 45-year-old thyroid cancer patients a more encouraging panorama of the disease with the new classification. Over the course of nearly 57 years, thyroid cancer staging has undergone remarkable changes, reaching a level of certainty that not only provides recommendations for safer treatments with less surgery and adjunctive measures but also improves survival rates and patient safety.

Keywords: classification; prognosis; risk; staging; surgery; thyroid cancer; tnm.

Figure 1. Historical developments in thyroid cancer diagnosis and treatments

Developments and discoveries that took place throughout these eight UICC and AJCC editions of TNM thyroid cancer staging might have been considered in writing a new edition. UICC: Union for International Cancer Control, AJCC: American Joint Committee on Cancer, TNM: Tumor, Node, and Metastasis, ATA: American Thyroid Association, TIRADS: Thyroid Imaging Reporting and Data System, FNAB: fine-needle aspiration biopsy, MRI: magnetic resonance imaging, CT: computed tomography, PET CT – FDG: positron emission tomography with fluorodeoxyglucose, RFA: radiofrequency ablation, TSH: thyroid-stimulating hormone, Tg: thyroglobulin Image Credit: Catalina Tobón-Ospina (Author)

Figure 2. T1 size has reduced over the years and across editions

The evolution and size reduction of T1 thyroid cancer over the years and across the eight editions of the AJCC and the UICC. TNM: Tumor, Node, and Metastasis, AJCC: American Joint Committee on Cancer, UICC: Union for International Cancer Control Image Credit: Catalina Tobón-Ospina (Author)

Figure 3. Stage classification according to age

WDTC: staging differences in patients younger (A) or older (B) than 55. A: A 52-year-old female patient with a 2.6 cm, right thyroid lobe papillary cancer, with positive nodes in the neck and mediastinum, will be considered as Stage I. Even though this patient also debuts with lung metastases, it will be considered as Stage II. B: A 58-year-old female patient with a 2.6 cm, right thyroid lobe papillary cancer, with positive nodes in the neck and mediastinum, will be considered as Stage II. However, if this patient also debuts with lung metastases, it will be considered Stage IVb. WDTC: well-differentiated thyroid cancer Modified and adapted with permission from Duque (2022) [50]