Endocrinol Metab.  2024 Jun;39(3):450-460. 10.3803/EnM.2023.1872.

Diagnostic Accuracy of Preoperative Radiologic Findings in Papillary Thyroid Microcarcinoma: Discrepancies with the Postoperative Pathologic Diagnosis and Implications for Clinical Outcomes

• Li Y
• Kwon SK
• Choi H
• Kim YH
• Kang S
• Jung KC
• Won JK
• Park DJ
• Park YJ
• Cho SW

• KMID: 2556637
• DOI: http://doi.org/10.3803/EnM.2023.1872

Abstract

Background
The diagnostic accuracy of preoperative radiologic findings in predicting the tumor characteristics and clinical outcomes of papillary thyroid microcarcinoma (PTMC) was evaluated across all risk groups.
Methods
In total, 939 PTMC patients, comprising both low-risk and non-low-risk groups, who underwent surgery were enrolled. The preoperative tumor size and lymph node metastasis (LNM) were evaluated by ultrasonography within 6 months before surgery and compared with the postoperative pathologic findings. Discrepancies between the preoperative and postoperative tumor sizes were analyzed, and clinical outcomes were assessed.
Results
The agreement rate between radiological and pathological tumor size was approximately 60%. Significant discrepancies were noted, including an increase in tumor size in 24.3% of cases. Notably, in 10.8% of patients, the postoperative tumor size exceeded 1 cm, despite being initially classified as 0.5 to 1.0 cm based on preoperative imaging. A postoperative tumor size >1 cm was associated with aggressive pathologic factors such as multiplicity, microscopic extrathyroidal extension, and LNM, as well as a higher risk of distant metastasis. In 30.1% of patients, LNM was diagnosed after surgery despite not being suspected before the procedure. This group was characterized by smaller metastatic foci and lower risks of distant metastasis or recurrence than patients with LNM detected both before and after surgery.
Conclusion
Among all risk groups of PTMCs, a subset showed an increase in tumor size, reaching 1 cm after surgery. These cases require special consideration due to their association with adverse clinical outcomes, including an elevated risk of distant metastasis.

Keyword

Papillary thyroid microcarcinoma; Radiologic diagnosis; Tumor size; Lymph node metastasis; Discrepancy

Figure

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  Fig. 1. Discrepancies of tumor size before and after surgery in papillary thyroid microcarcinoma. The difference between preoperative radiological and postoperative pathological tumor sizes is denoted as the “difference (D)” value. Agreement in tumor size was defined as a D value between –20% and 20%. D ≤–20% was categorized as a decrease in size, whereas D ≥20% were categorized as an increase in size. (A) Correlations between preoperative and postoperative tumor size. (B) Sankey diagram for differences in tumor size before and after surgery.

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  Fig. 2. Representative cases of the discrepancy between tumor size before and after surgery. (A, B) The first case involves a 55-year-old woman with papillary thyroid microcarcinoma (PTMC). An ultrasonographic (USG) image of the right thyroid gland reveals an ill-defined, irregular-shaped lesion that was initially evaluated as two separate nodules. The nodules measured 0.75 cm (A) and 0.47 cm (B). However, after surgery, it was confirmed that these nodules were actually part of a single tumor with a size of 1.9 cm. (C) The second case involves a 56-year-old woman with PTMC. A thyroid USG image shows a nodule with dense rim calcification, measured at 0.67 cm. However, postsurgery examination revealed a pathologic papillary thyroid carcinoma measuring 1.3 cm.

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  Fig. 3. Comparisons of survival outcomes based on tumor size and lymph node metastasis (LNM) in postoperative diagnosis. (A, B) Survival outcomes in relation to a tumor size of 1 cm based on the postoperative pathological measurement. Kaplan-Meier curves were utilized to analyze distant metastasis-free survival (A) and recurrence-free survival (B). (C, D) Survival outcomes between patients with LNM diagnosed both preoperatively and postoperatively (pre-post LNM), patients with LNM detected only at the time of postoperative evaluation (post-only LNM), and those without LNM detected postoperatively (no LNM). Kaplan-Meier curves were utilized to analyze distant metastasis-free survival (C) and recurrence-free survival (D). Post-T, postoperative tumor.

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