原发性肺粘液样肉瘤 (PPMS) 是一种罕见的低度恶性肿瘤，约占所有肺部肿瘤的 0.2%。尽管罕见，PPMS 具有独特的组织学特征和分子改变，特别是 EWSR1-CREB1 基因融合的存在。然而，其精确的组织来源仍然难以捉摸，给临床诊断带来了挑战。一名20岁的男性患者6个月前接受常规体检，发现肺部肿块。手术切除后，显微镜评估发现主要是短梭形肿瘤细胞，组织成束状、束状或网状图案。基质基质表现出丰富的粘蛋白，伴有淋巴细胞和浆细胞浸润，局部区域有明显的拉塞尔小体。免疫表型分析显示肿瘤细胞中波形蛋白和上皮膜抗原呈阳性表达，而平滑肌肌动蛋白和 S-100 等呈阴性。 Ki-67增殖指数约为5%。随后的第二代测序鉴定出特征性的 EWSR1-CREB1 基因融合体。明确的病理诊断确立了PPMS。该患者未接受辅助化疗或放疗，并且在 30 个月的随访期间保持无复发。我们报告一例罕见的 PPMS 病例，位于左肺叶叶间裂内，其特点是肿瘤间质内有 Russell 体形成，这是一种新型的 PPMS 病例。在 PPMS 中发现。此外，该病例的组织形态学特征凸显了其所带来的诊断挑战，因为它可能模仿炎性肌纤维母细胞瘤、骨骼外粘液样软骨肉瘤或血管外皮细胞瘤样纤维组织细胞瘤。因此，准确的诊断需要采用涉及形态学、免疫组织化学和分子分析的综合方法。© 2024。作者。

Primary pulmonary myxoid sarcoma (PPMS) is a rare, low-grade malignant tumor, constituting approximately 0.2% of all lung tumors. Despite its rarity, PPMS possesses distinctive histological features and molecular alterations, notably the presence of EWSR1-CREB1 gene fusion. However, its precise tissue origin remains elusive, posing challenges in clinical diagnosis.A 20-year-old male patient underwent a routine physical examination 6 months prior, revealing a pulmonary mass. Following surgical excision, microscopic evaluation unveiled predominantly short spindle-shaped tumor cells organized in a fascicular, beam-like, or reticular pattern. The stromal matrix exhibited abundant mucin, accompanied by lymphocytic and plasma cell infiltration, with Russell bodies evident in focal areas. Immunophenotypic profiling revealed positive expression of vimentin and epithelial membrane antigen in tumor cells, whereas smooth muscle actin and S-100, among others, were negative. Ki-67 proliferation index was approximately 5%. Subsequent second-generation sequencing identified the characteristic EWSR1-CREB1 gene fusion. The definitive pathological diagnosis established PPMS. The patient underwent no adjuvant chemotherapy or radiotherapy and remained recurrence-free during a 30-month follow-up period.We report a rare case of PPMS located within the left lung lobe interlobar fissure, featuring Russell body formation within the tumor stroma, a novel finding in PPMS. Furthermore, the histomorphological characteristics of this case highlight the diagnostic challenge it poses, as it may mimic inflammatory myofibroblastic tumor, extraskeletal myxoid chondrosarcoma, or hemangiopericytoma-like fibrous histiocytoma. Therefore, accurate diagnosis necessitates an integrated approach involving morphological, immunohistochemical, and molecular analyses.© 2024. The Author(s).