The EWSR1 rearrangements with unknown genes were detected in a high percentage of classic variants of papillary thyroid carcinoma. The small-cell carcinoma of the thyroid with Ewing family tumor elements (CEFTE) typically presents with EWSR1-FLI1 rearrangement suggesting the possible role of EWSR-FLI1 translocation in the loss of thyroid differentiation and acquisition of a small-cell phenotype. In order to determine the frequency and association of EWSR1 rearrangements, particularly the EWSR1-FLI1 fusion with clinicopathological features of papillary thyroid microcarcinoma (m-PTC) and the presence of small cells, we analyzed a series of 99 m-PTCs using the fluorescence in situ hybridization method. Ninety cases (90.9%) of m-PTC were positive for small cells. This group of m-PTC has shown more often invasive growth, lymphatics invasion, and moderate/extended intratumoral fibrosis. Three cases out of 99 were inconclusive for EWSR1 rearrangement. Eighty-nine (92.7%) and twenty-seven (28.1%) out of 96 m-PTC cases were positive for EWSR1 rearrangement and EWSR1-FLI1 fusion, respectively. m-PTC with classical architectural pattern presented more frequently with EWSR1 rearrangement relative to m-PTC with other patterns (p = 0.005). Other clinicopathological features were not related to the presence of EWSR1 rearrangement or EWSR1-FLI1 fusion. The percentage of small cells present significantly correlated with the percentage of cells positive for EWSR1-FLI1 fusion (p = 0.05) and EWSR1 rearrangement (p <0.001). EWSR1-FLI1 fusion is not rare in m-PTC and it is associated with the acquisition of small-cell phenotype. The EWSR1 gene rearrangement is a frequent event in m-PTC and is related to the classical pattern of m-PTC.

中文翻译：

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乳头状甲状腺微小癌中的 EWSR1 重排与经典形态学和小细胞表型的存在有关。

在高比例的甲状腺乳头状癌经典变异中检测到具有未知基因的 EWSR1 重排。具有尤文家族肿瘤成分的甲状腺小细胞癌 (CEFTE) 通常表现为 EWSR1-FLI1 重排，这表明 EWSR-FLI1 易位可能在甲状腺分化丧失和小细胞表型获得中发挥作用。为了确定 EWSR1 重排的频率和关联，特别是 EWSR1-FLI1 融合与甲状腺微小乳头状癌 (m-PTC) 的临床病理学特征和小细胞的存在，我们使用荧光分析了一系列 99 个 m-PTCs原位杂交法。90 例 (90.9%) m-PTC 小细胞呈阳性。这组 m-PTC 更常表现为侵袭性生长、淋巴管侵袭、和中度/扩展的瘤内纤维化。99 例中有 3 例对 EWSR1 重排没有定论。96 例 m-PTC 病例中有 89 例 (92.7%) 和 27 例 (28.1%) 分别对 EWSR1 重排和 EWSR1-FLI1 融合呈阳性。与具有其他模式的 m-PTC 相比，具有经典架构模式的 m-PTC 更频繁地出现 EWSR1 重排（p = 0.005）。其他临床病理学特征与 EWSR1 重排或 EWSR1-FLI1 融合的存在无关。存在的小细胞百分比与 EWSR1-FLI1 融合 (p = 0.05) 和 EWSR1 重排 (p <0.001) 阳性的细胞百分比显着相关。EWSR1-FLI1 融合在 m-PTC 中并不罕见，它与小细胞表型的获得有关。