Objective: To analyze the relationship between clinical characteristics and pathogenic gene mutations in multifocal papillary thyroid carcinoma (MPTC) and to investigate the proportion of independent primary tumors (IP) versus intrathyroidal metastases (ITM) in MPTC. Additionally, to explore the correlation between specific gene mutations and clinical features such as multifocality, tumor size, and lymph node metastasis.

Methods: Patients with multifocal thyroid tumor meeting inclusion criteria were consecutively enrolled. Two lesions per case were selected for preoperative ultrasound-guided fine-needle aspiration biopsy (FNAB). All lesions were pathologically confirmed as papillary thyroid carcinoma postoperatively. FNAB samples were subjected to multi-gene panel testing and classified into three groups based on mutational profiles of 26 thyroid-related genes: (1) identical mutations in both lesions (intrathyroidal metastasis), (2) completely discordant mutations (independent primary tumors), and (3) shared mutations with an additional mutation in one lesion (uncertain origin).

Results: Among 58 initially enrolled MPTC patients, 8 were excluded due to noncompliant specimens. The final cohort included 50 patients (37 females, 13 males) with a mean age of 42.64 ± 11.12 years. The median tumor diameter was 12.5 (IQR: 7.6, 20.0) mm, with 38.0% (19/50) classified as papillary thyroid microcarcinoma. A total of 128 mutations, 4 gene fusions, and 3 gene amplifications were detected across 100 qualified FNAB samples. BRAF V600E was the most prevalent mutation (84.0%, 84/100), followed by DICER1 (7.0%), PTEN (6.0%), and RET (4.0%). Identical mutational profiles (intrathyroidal metastasis) were observed in 64.0% (32/50) of cases, while 18.0% (9/50) exhibited completely discordant mutations (independent primary tumor). The remaining 18.0% (9/50) showed shared mutations with an additional mutation, predominantly in smaller lesions. The incidence of completely different mutations in ipsilateral lesions and bilateral lesions was different (p = 0.030). No significant correlation between BRAF V600E and clinical characteristics such as tumor size, multifocality, capsular invasion or lymph node metastasis (p > 0.05).

Conclusion: Multi-gene panel testing of preoperative FNAB samples effectively discriminates clonal relationships in MPTC, revealing distinct molecular profiles between ITM and IP. The high prevalence of BRAF V600E mutations and frequent clonal homogeneity underscore the necessity of comprehensive genetic profiling to guide personalized management. Routine multi-lesion sampling is advocated for optimizing risk stratification and surgical decision-making.

Keywords: genetic profiling; independent primary tumor; intrathyroidal metastasis; multifocal thyroid cancer.

© 2025 John Wiley & Sons Ltd.

目的: 分析多灶性乳头状甲状腺癌（MPTC）的临床特征与致病基因突变之间的关系，并探究独立原发肿瘤（IP）和甲状腺内转移（ITM）在MPTC中的比例。此外，探索特定基因突变与临床特征如多灶性、肿瘤大小和淋巴结转移的相关性。

方法: 符合纳入标准的多灶性甲状腺肿瘤患者连续入组。每例患者选择两个病灶进行术前超声引导下的细针抽吸活检（FNAB）。所有病灶术后病理确诊为乳头状甲状腺癌。FNAB样本进行多基因检测，并根据26个与甲状腺相关的基因突变谱型将病变分为三类：（1）两个病灶具有相同的突变（甲状腺内转移），（2）完全不同的突变（独立原发肿瘤），（3）两个病灶共享某些突变，但其中一个病灶有额外的突变（起源不确定）。

结果: 在最初入组的58例MPTC患者中，因样本不合规排除了8例。最终队列包括50名患者（37名女性和13名男性），平均年龄为42.64 ± 11.12岁。肿瘤直径中位数为12.5 (IQR: 7.6, 20.0) mm，其中38.0% (19/50) 被归类为乳头状甲状腺微小癌。在100个合格的FNAB样本中共检测到128种突变、4个基因融合和3个基因扩增。BRAF V600E是最常见的突变（占84.0%，共84/100），其次是DICER1 (7.0%)，PTEN (6.0%) 和RET (4.0%)。在50例患者中有64.0%（32/50）显示相同的突变谱型（甲状腺内转移），而18.0%（9/50）的患者则表现出完全不同的突变谱型（独立原发肿瘤）。剩余18.0%（9/50）的患者显示出共享某些突变但有一个病灶有额外突变的情况，这种情况主要发生在较小病变中。同一侧和双侧病灶之间完全不同突变的发生率存在差异 (p = 0.030)。未发现BRAF V600E与肿瘤大小、多灶性、包膜侵犯或淋巴结转移等临床特征的显著相关性（p > 0.05）。

结论: 在术前FNAB样本中进行多基因检测有效地区分了MPTC中的克隆关系，揭示了ITM和IP之间不同的分子谱型。BRAF V600E突变的高发率及频繁出现的克隆同质性强调了全面遗传谱分析在指导个性化管理方面的必要性。建议常规采集多病灶样本以优化风险分层和手术决策。

关键词: 遗传谱分析；独立原发肿瘤；甲状腺内转移；多灶性甲状腺癌。