Abstract：
UNASSIGNED: Superficial anaplastic lymphoma kinase (ALK)-rearranged myxoid spindle cell neoplasm (SAMS) is a recently described entity which coexpresses ALK, CD34, and commonly S100. These neoplasms are characterized morphologically by concentric spindle cell whorls and cords and are commonly set in an abundant myxoid to myxocollagenous stroma, thus mimicking perineurioma or hybrid nerve sheath tumor. EMA immunostain has been reported to be negative in SAMS which helps in excluding the latter entities. Herein, we report the first EMA-positive SAMS of the right leg in a 37-year-old female patient masquerading as perineurioma/hybrid nerve sheath tumor. The tumor morphologically was comprised of spindle cells arranged in loose whorls and short fascicles set in myxoid to collagenous stroma and coexpressed CD34 and EMA, reminiscent of perineurioma. S100 showed focal staining. ALK immunostain was subsequently performed and was positive. ALK gene rearrangement was identified by fluorescence in situ hybridization break-apart assay and was further confirmed by next-generation sequencing-based RNA sequencing demonstrating FLNA::ALK fusion, thus supporting the diagnosis of SAMS. In conclusion, EMA can be expressed in SAMS, thus posing as a diagnostic pitfall. ALK immunostain and molecular studies are essential for confirming the diagnosis of SAMS and excluding potential mimickers, particularly perineurioma or hybrid nerve sheath tumor.
摘要：
■浅表性间变性淋巴瘤激酶（ALK）-重排的粘液样梭形细胞肿瘤（SAMS）是最近描述的共表达ALK的实体，CD34，通常是S100。这些肿瘤的形态特征是同心梭形细胞轮和索，通常设置在一个丰富的粘液样到粘液胶质基质中，从而模仿神经鞘瘤或混合神经鞘瘤。据报道，EMA免疫染色在SAMS中是阴性的，这有助于排除后者。在这里，我们报告了一名37岁女性患者的右腿EMA阳性SAMS，该患者伪装成神经鞘瘤/混合神经鞘瘤。在形态上，肿瘤由梭形细胞组成，这些细胞排列在松散的轮状和短束中，与胶原间质成粘液状，并共同表达CD34和EMA，让人想起神经鞘瘤。S100显示病灶染色。随后进行ALK免疫染色并且是阳性的。ALK基因重排通过荧光原位杂交分裂分析鉴定，并通过下一代基于测序的RNA测序进一步证实，证明FLNA::ALK融合，从而支持SAMS的诊断。总之,EMA可以在SAMS中表达，因此冒充诊断陷阱。ALK免疫染色和分子研究对于确认SAMS的诊断和排除潜在的模拟者至关重要。特别是神经鞘瘤或混合神经鞘瘤。
