Objective: To investigate the clinicopathological features, immunophenotype, diagnosis and differential diagnosis of SRF-rearranged cellular perivascular myoid tumor. Methods: Two cases of SRF-rearranged cellular perivascular myoid tumor diagnosed in the Department of Pathology, Fudan University Shanghai Cancer Center from October 2021 to March 2022 were collected. Immunohistochemical staining, fluorescence in-situ hybridization (FISH) and next-generation sequencing (NGS) were performed, and the literature was reviewed. Results: Case 1, a 3-month-old boy presented with a painless tumor of the scalp, measuring about 2 cm in diameter. Case 2, a 3-year-old girl complained with a painless tumor of the knee, measuring approximately 1.5 cm in diameter. Microscopically, the tumor had a clear boundary and showed multinodular growth. The tumor was mainly composed of spindle cells arranged in long intersecting fascicles associated with thin, slit-like or branching ectatic vessels, focally forming hemangiopericytoma-like appearance. The tumor cells were abundant, but there was no obvious atypia. Mitotic figures (3-4/10 HPF) were noted. H-caldesmon and SMA were positive in both cases. Case 1 showed diffuse and strong positivity for Desmin, and focally for CKpan. Ki-67 proliferation index was 20% and 30%, respectively. FISH displayed NCOA2 gene translocation in case 1 and the RELA gene translocation in case 2. NGS detected the SRF-NCOA2 gene fusion in case 1 and the SRF-RELA gene fusion in case 2. Both patients underwent local excisions. During the follow-up of 5-14 months, case 1 had no local recurrence, while case 2 developed local recurrence 1 year post operatively. Conclusions: SRF-rearranged cellular perivascular myoid tumor is a novel variant of perivascular cell tumor, which tends to occur in children and adolescents. The tumor forms a broad morphologic spectrum ranging from a pericytic pattern to a myoid pattern, and include hybrid tumors with a mixture of pericytic and myoid patterns. Due to its diffuse hypercellularity and increased mitotic figures and smooth muscle-like immunophenotype, the tumor is easy to be misdiagnosed as myogenic sarcomas. The tumor usually pursues a benign clinical course and rare cases may locally recur.
目的： 探讨SRF易位富于细胞性血管周肌样肿瘤的临床病理学特征、免疫表型、诊断及鉴别诊断。 方法： 收集复旦大学附属肿瘤医院病理科2021年10月至2022年3月诊断的2例SRF易位富于细胞性血管周肌样肿瘤病例，分析其临床病理学资料，行免疫组织化学染色、荧光原位杂交（FISH）和二代测序，并复习相关文献。 结果： 例1，患儿男，3个月，头皮皮下无痛性肿块，直径约2 cm。例2，患儿女，3岁，膝关节处无痛性肿物，直径约1.5 cm。镜下观察，肿瘤边界清楚，呈多结节状生长；主要由长条束状或交叉束状排列梭形细胞组成，间质中可见裂隙状或分支状扩张的薄壁血管，局部形成血管外皮瘤样结构。瘤细胞丰富，但无明显异型性，可见核分裂象（3~4个/10 HPF）。2例均表达h-caldesmon和平滑肌肌动蛋白；例1结蛋白弥漫强阳性，局灶表达广谱细胞角蛋白；Ki-67阳性指数分别为20%和30%。FISH检测显示例1存在NCOA2基因易位，例2存在RELA基因易位。二代测序检测显示例1存在SRF-NCOA2基因融合，例2存在SRF-RELA基因融合。2例均行局部肿块切除，随访5~14个月，例1无局部复发，例2术后1年发生局部复发。 结论： SRF易位富于细胞性血管周肌样肿瘤是血管周细胞肿瘤的一种新变异型，好发于儿童和青少年，其形成从血管周细胞肿瘤至肌样肿瘤及混杂性血管周-肌样肿瘤的广泛形态学谱系。因瘤细胞丰富，可见活跃的核分裂象，且呈平滑肌样免疫表型，容易误诊为肌源性肉瘤。该肿瘤大多为良性，少数可复发。.