骨化性纤维粘液样肿瘤（OFMT）是一种罕见的组织发生不确定的软组织肿瘤。大多数 OFMT 具有良性行为，并且许多 OFMT 含有涉及 PHD 指蛋白 1 (PHF1) 的基因融合，例如 EP400::PHF1、MEAF6::PHF1、EPC1::PHF1 和 PHF1::TFE3。 PHF1::TFE3 融合是独特的，因为 PHF1 位于 5'，而不是其他融合中的 3'。在本研究中，我们描述了 2 例含有 PHF1::TFE3 融合的 OFMT 病例，并回顾了 13 个已发表的病例。使用 RNA 下一代测序和免疫组织化学对两例 PHF1::TFE3 阳性 OFMT 进行了研究。大多数 (12/15)我们研究的 PHF1::TFE3 OFMT 位于四肢近端和远端，具有多结节生长模式。仅1例（1/10）周围有骨壳。 12 例中有 8 例 (66.7%) 发现形态学上与硬化性上皮样纤维肉瘤或低度恶性纤维粘液样肉瘤相似的区域。 11 例 (11/15 [73.3%]) 基于超过 2/50 高倍视野有丝分裂图、细胞数量增加或坏死的存在而被视为恶性。在9例有随访数据的病例中，2例患者因疾病死亡（有转移），1例患者因转移而存活，1例患者多次局部复发。因为除了OFMT中的所有PHF1融合外，PHF1都位于3' PHF1::TFE3，不同的驱动分子改变表明具有 3'-PHF1 融合的 OFMT 和具有 PHF1::TFE3 的 OFMT 是不同的肿瘤。免疫组织化学证实所有 PHF1::TFE3 OFMT 中均表达 TFE3。由于 PHF1::TFE3 阳性 OFMT 的有丝分裂数和肿瘤细胞结构增加，且转移率高，因此使用 PHF1::TFE3 阳性纤维粘液样肉瘤这一名称可能比较合适。© 作者 2024。由牛津大学出版社出版代表美国临床病理学会。版权所有。如需商业重复使用，请联系 reprints@oup.com 获取转载和转载的翻译权。所有其他权限都可以通过我们网站文章页面上的权限链接通过我们的 RightsLink 服务获得 - 如需更多信息，请联系journals.permissions@oup.com。

Ossifying fibromyxoid tumor (OFMT) is a rare soft tissue neoplasm of uncertain histogenesis. Most OFMTs have benign behavior, and many harbor gene fusions involving the PHD finger protein 1 (PHF1), such as EP400::PHF1, MEAF6::PHF1, EPC1::PHF1, and PHF1::TFE3. The PHF1::TFE3 fusion is unique because PHF1 is at 5' instead of residing at 3' in the other fusions. In this study, we describe 2 cases of OFMT harboring PHF1::TFE3 fusions and review 13 published cases.Two cases of PHF1::TFE3-positive OFMT were investigated using RNA Next-Generation Sequencing and immunohistochemistry.Most (12/15) of the PHF1::TFE3 OFMTs we studied were located at proximal and distal extremities, with a multinodular growth pattern. Only 1 case (1/10) had a shell of bone at the periphery. Areas morphologically similar to sclerosing epithelioid fibrosarcoma or low-grade fibromyxoid sarcoma were found in 8 of 12 (66.7%) cases. Eleven cases (11/15 [73.3%]) were regarded as malignant based on more than 2/50 high-power field mitotic figures, increased cellularity, or the presence of necrosis. Among the 9 cases with follow-up data, 2 patients died of disease (with metastases), 1 patient is alive with metastases, and 1 patient had multiple local recurrences.Because PHF1 is located at 3' in all the PHF1 fusions in OFMTs except PHF1::TFE3, the different driver molecular alterations suggest that OFMTs with 3'-PHF1 fusions and OFMTs with PHF1::TFE3 are different tumors. Immunohistochemistry confirmed TFE3 expression in all PHF1::TFE3 OFMTs. Because PHF1::TFE3-positive OFMTs have increased mitotic figures and tumor cellularity, with a high rate of metastasis, using the name PHF1::TFE3 positive fibromyxoid sarcoma may be appropriate.© The Author(s) 2024. Published by Oxford University Press on behalf of American Society for Clinical Pathology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.