Objective. Multifocality within an affected lobe (unilateral multifocality) or two lobes (bilaterality) is commonly denoted as multifocality without differentiation. Recently, there has been molecular evidence indicating that unilateral multifocality and bilaterality could be two different entities. However, few studies concerning the comparison between these two different multifocality entities have been reported. Design. A retrospective cohort study. Methods. From 2010 to 2013, in total, 949 consecutive patients with papillary thyroid microcarcinoma (PTMC) were enrolled and further divided into four groups based on multifocality status. Unilateral multifocality and bilaterality were analyzed by binary logistic regression along with other clinicopathological factors. Results. Unilateral multifocality, instead of bilaterality, was correlated with central neck metastasis (CNM) in both univariate and multivariate analyses. Group IV (unilateral multifocality and bilaterality coexist) had the highest CNM rate. Group III (unilateral multifocality) had a higher CNM rate than group II (bilaterality, single lesion in each lobe), with a significant difference (). Similar lateral neck metastasis tendency was observed among the four groups. In the multivariate analysis, only unilateral multifocality and bilaterality which coexisted were correlated with CNM. Moreover, 9 cases had a recurrence, with the recurrence rate ranking top in group IV (3.6%), second in group III (2.8%), and third in group II (1.2%). The difference was significant (). Conclusion. Unilateral multifocality and bilaterality could be two different multifocal entities in patients with PTMC. Unilateral multifocality serving as a prognostic factor indicated a worse prognosis than bilaterality on neck metastasis. When the two factors coexisted in PTMC, patients had the highest risk of CNM and possibly local recurrence compared with those with either risk factor alone.

中文翻译：

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单侧多灶性和双侧性可能是甲状腺微小乳头状癌患者的两种不同的多灶性实体。


客观的。受影响的肺叶内的多灶性（单侧多灶性）或两个叶内（双侧性）通常表示为不区分的多灶性。最近，有分子证据表明单侧多焦点和双边可能是两个不同的实体。然而，关于这两种不同的多焦点实体之间的比较的研究很少被报道。设计。一项回顾性队列研究。方法。从2010年到2013年，总共连续登记了949名甲状腺微小乳头状癌（PTMC）患者，并根据多灶性状态进一步分为四组。通过二元逻辑回归分析单侧多灶性和双边性以及其他临床病理因素。结果。在单变量和多变量分析中，单侧多灶性而非双侧性与中央颈转移（CNM）相关。 IV组（单侧多焦点和双侧共存）CNM率最高。 III组（单侧多灶性）的CNM率高于II组（双侧，每个肺叶单个病灶），差异显着（ ）。四组之间观察到相似的颈侧转移倾向。在多变量分析中，只有单侧多焦点和双侧共存与CNM相关。另有9例复发，复发率IV组最高（3.6%），III组第二（2.8%），II组第三（1.2%）。 差异显着（ ）。结论。单侧多灶性和双侧性可能是 PTMC 患者的两种不同的多灶性实体。单侧多灶性作为预后因素表明颈部转移的预后比双侧性差。当 PTMC 中这两个因素共存时，与单独具有任一危险因素的患者相比，患者发生 CNM 的风险最高，并且可能出现局部复发。