1. EMC好发于中老年人,男性多于女性,儿童罕见;肿瘤通常表现为深部皮下的无痛性肿物,好发于近端肢体,其它包括躯干或头颈部等;
2. 瘤体直径通常较大,平均约7cm,界限相对清楚,伴或者不伴有包膜;切面多结节状,有光泽,可见出血,罕见坏死;高级别富于细胞的肿瘤肉质感较强;
3. 镜下肿瘤由纤维性间质分割成多结节状生长,结节内瘤细胞上皮样或短梭形,呈索状、链状、星芒状或梁状或网状排列分布于丰富的软骨黏液性基质之中;
4.瘤细胞大小较一致,胞浆嗜酸性,核圆形或卵圆形,染色质深无核仁;富于细胞的亚型显示成片的瘤细胞伴稀少的黏液性间质;
5.核分裂象通常<2个/10HPF;高级别肿瘤显示瘤细胞胞浆更丰富(可见横纹肌样细胞),密度高,核异型性,明显的核分裂象。
软组织软骨瘤:主要发生于远端肢体;除了黏液样基质之外更常见为透明软骨基质;瘤细胞位于界限清楚的透明软骨陷窝之内,遗传学上无NR4A3基因重排;
软组织肌上皮瘤/混合瘤:瘤细胞构成异质性强,呈上皮样、浆细胞样、透明细胞样和梭形细胞;免疫组化染色表达CK、EMA、S100蛋白和SOX10等,可表达SMA、calponin以及GFAP和P63等,值得注意的是软组织肌上皮瘤遗传学上可显示EWSR1基因重排,因此单纯应用EWSR1 融合分离探针的FISH检测无法对两者进行区分,进行NR4A3基因重排检测可助于鉴别诊断;
脊索瘤:典型的发生于脊柱中线骨部位,非常罕见于骨外和硬膜内,或转移至软组织;除了表达S100蛋白之外,尚表达CK和EMA,特征性的表达brachyury,差分化的肿瘤可出现INI-1表达缺失,遗传学上无NR4A3基因重排。
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