富含组织细胞的横纹肌母细胞性肿瘤临床病理及分子遗传学分析

Histiocyte-rich rhabdomyoblastic tumor:a clinicopathological and molecular genetic analysis

目的:探讨富含组织细胞的横纹肌母细胞性肿瘤(histiocyte-rich rhabdomyoblastic tumor,HRRMT)的临床病理特征、分子遗传学特点、诊断及鉴别诊断。方法:收集2020—2021年福建省立医院及福建中医药大学附属人民医院共2例HRRMT的临床资料,观察其组织病理学及免疫组织化学染色,基于二代测序技术分析其遗传学改变,并复习文献。结果:2例大体均表现为界限清楚的实性结节,质软。镜下均见肿瘤具有含淋巴细胞聚集的纤维性假包膜,局部侵犯周围骨骼肌组织,肿瘤细胞呈梭形至上皮样,伴大量泡沫样组织细胞浸润,未见坏死及核分裂象。免疫表型上,肿瘤细胞表达结蛋白,至少表达1个骨骼肌标记(Myogenin或MyoD1),h-caldesmon、间变性淋巴瘤激酶(ALK)及平滑肌肌动蛋白(SMA)阴性,Ki-67阳性指数<5%。二代测序检测发现,其中1例具有KRAS(G12D)突变及MSH3(Q470 *)突变。 结论:HRRMT是新近描述的一种恶性潜能不确定的骨骼肌肿瘤,诊断及鉴别诊断依赖于形态学及免疫组织化学染色,暂未发现特异性分子遗传学改变。

Objective To investigate the clinicopathologic and molecular genetic characteristics,diagnosis,differential diagnosis,treatment and prognosis of histiocyte-rich rhabdomyoblastic tumor(HRRMT).Methods The clinical data of two cases of HRRMT diagnosed in Fujian Provincial Hospital and Fujian University of Traditional Chinese Medicine Affiliated People′s Hospital from 2020 to 2021 were collected.Histopathology and immunohistochemical(IHC)staining were used to assess morphological changes;the genetic changes were analyzed with next-generation sequencing.The relevant literature was reviewed.Results Both cases showed well-defined solid nodules and soft masses.Microscopically,the tumors had a fibrous pseudocapsule with lymphocytic aggregation,and locally invaded the surrounding skeletal muscle tissue,and the tumor cells were fusiform to epithelioid with an intensive foamy histiocytic infiltrate.No necrosis or mitosis was observed.Immunophenotyping showed the tumor cells were positive for desmin,either one or both skeletal muscle markers(myogenin or MyoD1),and negative for h-caldesmon,ALK and SMA.The Ki-67 index was<5%.Using next-generation sequencing,one case was found to harbour KRAS(G12D)and MSH3(Q470*)mutations.Conclusions HRRMT is a newly described skeletal muscle tumor with uncertain malignant potential.Its diagnosis and differential diagnosis depend on morphologic and IHC staining.No specific molecular genetics changes have been identified so far.