Impact of reclassification of oncocytic and follicular thyroid carcinoma by the 2022 who classification

Merel Stegenga; Lindsey Oudijk; Velsen Evert Van; Marco Medici; Frederik Verburg; Ginhoven Tessa Van; Robin Peeters; Kemenade Folkert van; Visser W. Edward

doi:10.1530/endoabs.101.OP-03-01

OP-03-01

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Endocrine Abstracts (2024) 101 OP03-01 | DOI: 10.1530/endoabs.101.OP-03-01

ETA2024 Oral Presentations Oral Session 3: Young Investigators/Clinical and Translational (6 abstracts)

Impact of reclassification of oncocytic and follicular thyroid carcinoma by the 2022 who classification

Merel Stegenga ¹ , Lindsey Oudijk ² , Evert Van Velsen ³ , Marco Medici ⁴ , Frederik Verburg ⁵ , Tessa Van Ginhoven ⁶ , Robin Peeters ⁷ , Folkert van Kemenade ⁸ & W. Edward Visser ⁹

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¹Erasmus Medical Center, Rotterdam, Rotterdam, Netherlands; ²Erasmus Medical Center, Erasmus Medical Center, Pathology, Rotterdam, Netherlands; ³Academic Center for Thyroid Diseases, Department of Internal Medicine, Erasmus Medical Center, Erasmus Mc, Internal Medicine, Rotterdam, Netherlands; ⁴Radboud University Medical Center, Nijmegen, Erasmus Medical Center, Rotterdam, Department of Internal Medicine, Radboud University Medical Center, Nijmegen, Netherlands; ⁵Erasmus Mc, Radiology and Nuclear Medicine, Radiology and Nuclear Medicine, Rotterdam, Netherlands; ⁶Academic Center for Thyroid Diseases, Department of Surgery, Erasmus Medical Center, Erasmus Mc, Surgery, Rotterdam, Netherlands; ⁷Academic Center for Thyroid Diseases, Department of Endocrinology, Erasmus, Department of Internal Medicine,, Rotterdam, Netherlands; ⁸Academic Center for Thyroid Diseases, Department of Pathology, Erasmus Medical Center, Erasmus Medical Center, Pathology, Rotterdam, Netherlands; ⁹Erasmus Medical Center, Academic Center for Thyroid Diseases, Department of Internal Medicine, Academic Center for Thyroid Diseases, Rotterdam, Netherlands

Introduction: The 2022 WHO Classification categorizes oncocytic (OTC) and follicular thyroid carcinoma (FTC) based on the degree of capsular and vascular invasion into minimally invasive (MI), encapsulated angioinvasive (EA) and widely invasive tumors (WI). While associations with clinical outcomes have extensively been studied in FTC, for OTC robust clinical data is lacking. The aim of this study is to investigate the newly defined categorization by the 2022 WHO Classification on clinical outcomes in OTC compared to FTC.

Methods: All adult FTC and OTC patients treated at a tertiary referral hospital between 2000 and 2016 were retrospectively included (n = 141). All tumors were thoroughly revised independently by two pathologists applying the 2004 and 2022 WHO Classification. Kaplan-Meier curves were used to study the association of the 2004 and 2022 WHO Classification with overall survival (OS), disease-specific survival (DSS), recurrence-free survival (RFS) and incidence of radioactive iodine (RAI-) refractory disease.

Results: 52 OTC and 89 FTC patients were included. OTC patients were older at diagnosis (61.7 years vs 51.7 years), and more often male (50% vs 23.6%). After revision, 28.8% of OTC tumors were reclassified (7 from MI to EA and 8 from WI to EA), resulting in 5 MIOTC, 15 EAOTC and 32 WIOTC. In FTC, 38.2% tumors were reclassified (20 from MI to EA and 14 from WI to EA), resulting in 32 MIFTC, 34 EAFTC and 23 WIFTC. Compared to the 2004 WHO Classification, the 2022 WHO classification showed a better risk stratification for DSS, with an intermediate prognosis in EAOTC and EAFTC. Ten-year DSS with the 2022 WHO Classification were 100% for MIOTC, 92.3% for EAOTC and 56.5% for WIOTC, compared to 100% (MIOTC) and 64.2% (WIOTC) following the 2004 WHO Classification. Similar trends were observed for RAI-refractory disease, but not for OS and RFS.

Conclusion: To our knowledge, our study is the first to show that classification of OTC and FTC into three subcategories based on the extent of invasiveness (i.e. MI, EA and WI), as defined by the 2022 WHO Classification, substantially improves discrimination between low, intermediate and high risk patients, especially for DSS and RAI-refractory disease.