Feasibility Study of Ultrasonographic Criteria for Microscopic and Macroscopic Extra-Thyroidal Extension Based on Thyroid Capsular Continuity and Tumor Contour in Patients with Papillary Thyroid Carcinomas

Abstract Our purpose was to evaluate the feasibility of using ultrasonographic criteria of thyroid capsular continuity and tumor contour to differentiate macroscopic extra-thyroidal extension (ETE) from microscopic ETE, as well as non-ETE from ETE. On ultrasonography, we evaluated thyroid capsular continuity (C0 = continuous, C1 = discontinuous, C2 = invisible), and thyroid tumor contour (P0 = in normal parenchyma, P1 = abutting, P2 = bulging), which were grouped into type 1–9 classifications. Either C1–2 or P1–2 was more prevalent in ETE than non-ETE. C1 and P2 tended to be associated with macroscopic ETE, whereas C0 and P1 were significantly associated with microscopic ETE. Types 6, 8 and 9 were more likely to have ETE than non-ETE; type 6 (C1 P2) and type 9 (C2 P2) were significantly associated with macroscopic ETE, whereas type 8 (C2 P1) was associated more with microscopic ETE. Macroscopic and microscopic ETE, as well as non-ETE and ETE, can be differentiated using these pre-operative ultrasonographic criteria.