Objective: To investigate the clinicopathological features, differential diagnosis, treatment and prognosis of dedifferentiated liposarcoma with rhabdomyoblastic differentiation. Methods: Six cases of retroperitoneal dedifferentiated liposarcoma with rhabdomyoblastic features were collected from December 2014 to August 2017 at Peking University International Hospital. The clinical manifestations, histomorphology, immunophenotype, treatment and follow-up data were analyzed, and relevant literature reviewed. Results: The six patients included two males and four females, with age range of 47 to 66 years (mean 56 years). One case was primary and the five cases were recurred; four cases received radiotherapy and/or chemotherapy. The tumor diameters were 10 to 30 cm. Microscopically, the dedifferentiated areas were well demarcated from the well-differentiated areas, and resembled malignant fibrous histiocytoma, fibrosarcoma or solitary fibrous tumor with obvious mitotic figures or necrosis. Rhabdomyoblastic cells made up 10% to 30% of dedifferentiated area, and were scattered or focally distributed, being rounded, band-like or spindled, mostly with abundant eosinophilic cytoplasm. No striated structure was found, and the nucleis were rounded, oval or irregular shape with central or eccentric prominent nucleoli. Rare rhabdomyoblastic cells were lymphocytoid. The tumors encroached the muscular layer of intestinal wall in two cases and perirenal adipose tissue in one case. By immunohistochemical staining, the rhabdomyoblastic cells of all cases were all positive for desmin, myogenin, myoD1 and SMA; S-100 protein was expressed in one case (1/6). Well-differentiated area in two cases and dedifferentiated areas in all six cases were positive for MDM2, CDK4 and p16. After resection of the tumor and adjacent organs, one case recurred three months later, but there was no distant metastasis. Conclusions: Dedifferentiated liposarcoma with rhabdomyoblastic differentiation is a rare dedifferentiated liposarcoma. Pathological diagnosis is based on morphology, with supplementary immunohistochemical or molecular evaluation for further differential diagnosis. Multiple relapses may occur after surgical ablation plus adjuvant therapy.
目的： 分析伴横纹肌分化的去分化脂肪肉瘤临床病理学特征、鉴别诊断和治疗。 方法： 收集2014年12月至2017年8月就诊于北京大学国际医院的6例腹膜后伴横纹肌分化去分化脂肪肉瘤患者资料，包括临床表现、组织学形态、免疫组织化学表型、治疗及预后情况，并复习相关文献。 结果： 男性2例，女性4例；年龄47～66岁，平均年龄56岁。1例为原发病例，5例多次复发，4例曾行放疗和/或化疗。肿瘤最大径10～30 cm，镜下去分化区与高分化区分布界限清晰，表现为恶性纤维组织细胞瘤样、纤维肉瘤样或孤立性纤维性肿瘤样，核分裂象易见，可伴坏死；其间见散在或片灶状横纹肌分化细胞，占去分化区面积10%～30%，细胞类圆形、带状或梭形，横纹不易观察，大多胞质丰富，嗜酸红染，核形多样、居中或偏位，核仁易见，少数细胞呈小圆形、胞质少的淋巴细胞样。2例累及肠壁肌层，1例累及肾周脂肪囊。免疫组织化学染色：横纹肌分化区6例均表达结蛋白、肌浆蛋白和肌调节蛋白，1例表达平滑肌肌动蛋白和S－100蛋白；2例高分化区和6例去分化区均表达MDM2、CDK4和p16。手术切除肿瘤及邻近受侵器官，1例术后3个月再次复发，尚无远处转移病例。 结论： 伴横纹肌分化的去分化脂肪肉瘤属少见的去分化脂肪肉瘤，诊断以形态学为基础、辅以免疫组织化学或基因检测进一步诊断及鉴别诊断，手术切除加辅助放化疗仍可多次复发。.
Keywords: Immunohistochemistry; Liposarcoma; Muscle, striated; Retroperitoneal neoplasms.