The Luo-Dingyuan Thyroid Vascular-Lymphatic Segmentation Classification: A Functional Anatomy-Based Framework to Facilitate Precision Management and Thyroid Function Preservation.

Background: Hypothyroidism remains a common and clinically significant consequence of thyroid surgery, frequently necessitating long-term or lifelong thyroid hormone replacement therapy, which may be associated with adverse effects on cardiovascular health and bone metabolism. In the era of treatment de-escalation, active surveillance and local ablation have emerged as important management. However, both require precise anatomical localization and rational definition of treatment boundaries. Therefore, a precise anatomical framework that enables function-preserving management without compromising oncologic safety is urgently needed. The study proposes and comprehensively describes a novel, anatomy-based segmental classification of thyroid, the Luo-Dingyuan Segmental Classification (Luo Segmental Classification), to explore its potential clinical applications. Methods: The Luo Segmental Classification was developed through an integrated analysis of classical thyroid anatomy, vascular territories, and lymphatic drainage patterns. Each thyroid lobe is divided longitudinally into upper, middle, and lower thirds and further subdivided into anterior and posterior segments according to depth and vascular-lymphatic orientation, resulting in six reproducible segments per lobe. The isthmus and pyramidal lobe are defined as an independent anatomical unit. Potential clinical applications were evaluated conceptually in imaging, surgery, active surveillance, and ablation. Results: The thyroid can be consistently divided into anatomically and functionally meaningful segments corresponding to distinct vascular and lymphatic territories. Based on this principle, the classification enabled standardized anatomical localization of thyroid nodules across ultrasonography (US), computed tomography (CT), and magnetic resonance imaging (MRI). Segment-based localization allowed precise description of tumor position, facilitated individualized treatment planning, and provided a unified anatomical language bridging radiology, surgery, pathology, and interventional therapy. Overall, this framework supported standardized reporting, individualized management, and potential reduction of unnecessary thyroid tissue loss and permanent hypothyroidism. Conclusion: The Luo Segmental Classification provides an anatomy-based framework to promote precise and individualized management of thyroid cancer, support function-preserving strategies, and address unmet clinical needs.