摘要目的:探讨原发性骨外骨肉瘤（extraskeletal osteosarcoma， ESOS）的临床病理、免疫组织化学及分子病理学特征。方法:收集2003年1月至2019年1月福建省立医院诊治的10例ESOS，进行HE、免疫组织化学染色及分子病理学检测，并电话随访及复习相关文献。结果:3例女性和7例男性，年龄36~85岁（平均年龄60岁），肿块大小5.5~17.5 cm（平均11.0 cm）。低倍镜下，肿瘤呈结节状、片状、分叶状，肿瘤由梭形细胞、肿瘤性骨样组织、软骨样组织构成，三者比例多少不等，并相互移行，其中见异型性梭形细胞直接产生骨样组织。免疫表型：肿瘤细胞呈SATB2部分阳性（9/9），α-平滑肌肌动蛋白（4/10）和上皮细胞膜抗原（1/10）灶性阳性，Ki-67阳性指数10%~50%，结蛋白、CD68、S-100蛋白、SOX10、HMB45、CD117、DOG1、CD34、广谱细胞角蛋白（CKpan）、GATA3及PAX8均阴性。分子病理检测：未检测到MDM2/CDK4基因扩增信号（0/6）；未见SSX18基因分离信号（0/5）；未检测到C-KIT和PDGFR-α突变信号（0/3）。结论:ESOS属于骨外成骨性肿瘤，诊断需临床、影像、病理学相结合，必要时免疫组织化学及分子病理检测辅助诊断。

abstractsObjective:To investigate the clinicopathologic features, differential diagnosis, immunohistochemical profiles and molecular characteristics of primary extraskeletal osteosarcoma (ESOS).Methods:Ten cases of ESOS diagnosed and treated in Fujian Provincial Hospital, Fuzhou, China from January 2003 to January 2019 were collected and subjected to immunohistochemical staining and molecular analyses. The patients were followed up by telephone interview. Relative literature was also reviewed to assess the characteristics of this tumor.Results:The ten cases occurred in 3 women and 7 men, aged from 36 to 85 years (median, 60 years). The sizes of these tumors ranged from 5.5 to 17.5 cm (median, 11.0 cm). Histologically, at low magnification, the tumors were nodular, leafy and lobulated. They were composed of spindle cells, neoplastic osteoid cells, and cartilage tissues, with unequally-proportional mixture of these components. The three components intermingled with each other. Immunohistochemistry profiling showed that the tumor cells were positive for SATB2 (9/9), while α-SMA (4/10) and EMA (1/10) stains were focally positive. Ki-67 proliferation index was 10%?50%. Desmin, CD68, S-100 protein, SOX10, HMB45, CD117, DOG1, CD34, CKpan, GATA3 and PAX8 stains were negative. MDM2/CDK4 gene amplification signals were not detected in the 6 cases (0/6), which were subjected to the FISH. The SSX18 break-apart signal and the C-KIT and PDGFR-α mutations were not detected (0/5 and 0/3, respectively). Conclusions:Primary ESOS is an extra-osseous osteogenic tumor. The diagnosis is mainly dependent on clinical, radiological and pathological characteristics. Immunohistochemistry and molecular profiling are helpful for making the correct diagnosis.