Spindle cell/sclerosing rhabdomyosarcoma (RMS), characterized by MYOD1 (L122R) mutation in a subset of cases is a newly described subtype of RMS. Presently, there is no documentation of cytomorphological features, especially of sclerosing RMS. Case 1: A 24-year-old male presented with pain and swelling in his wrist for a one-year duration. MRI revealed a well-defined soft tissue lesion measuring 5.3 cm, encasing the lower end of the ulna. Fine-needle aspiration cytology (FNAC) smears revealed clusters of tumor cells with round to oval to spindle-shaped nuclei, scant to moderate amount of cytoplasm with the wisps of the metachromatic stroma. Histopathological examination revealed a malignant tumor comprising cells with polygonal to spindle-shaped nuclei, arranged in a sclerotic stroma. Immunohistochemically, the tumor cells were positive for desmin, myogenin, and MYOD1. A diagnosis of sclerosing RMS was offered. Furthermore, the tumor revealed MYOD1 (L122R) mutation. Case 2: A 43-year-old male presented with a 4-month history of “nasal stuffiness” and pressure. Imaging revealed a poorly defined infiltrative lesion in his nasal cavity. FNAC smears revealed loose and tightly cohesive clusters of malignant cells with oval to spindle-shaped nuclei, a moderate amount of ill-defined bluish to finely vacuolated cytoplasm, and focal streak artifact with interspersed stromal fragments. Histopathological examination revealed a malignant tumor composed of oval to spindle-shaped nuclei, embedded in a variably hyalinized stroma. Immunohistochemically, the tumor cells were positive for desmin, and myogenin. Diagnosis of spindle cell/sclerosing RMS was offered. The present study constitutes one of the first documentation of cytomorphological features of two rare cases of spindle cell/sclerosing RMS. The differential diagnoses and treatment-related implications are presented.

中文翻译：

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梭形细胞/硬化性横纹肌肉瘤的细胞形态学，包括 MYOD1 (LI22R) 突变结果

梭形细胞/硬化性横纹肌肉瘤 (RMS)，以MYOD1 (L122R)为特征部分病例中的突变是新描述的 RMS 亚型。目前，没有关于细胞形态学特征的文件，尤其是硬化性 RMS。病例 1：一名 24 岁男性，因手腕疼痛和肿胀 1 年就诊。MRI 显示一个明确的软组织病变，尺寸为 5.3 厘米，包围了尺骨的下端。细针抽吸细胞学 (FNAC) 涂片显示肿瘤细胞簇，核圆形至椭圆形至梭形，细胞质稀少至中等，伴有异染间质。组织病理学检查显示恶性肿瘤，其细胞核呈多角形至梭形，排列在硬化间质中。免疫组化显示，肿瘤细胞结蛋白、肌生成素和MYOD1 阳性. 提供了硬化性 RMS 的诊断。此外，肿瘤显示MYOD1 (L122R)突变。病例 2：43 岁男性，因“鼻塞”和压力 4 个月就诊。影像显示他的鼻腔内有一个边界不清的浸润性病变。FNAC 涂片显示恶性细胞团松散而紧密结合，细胞核呈椭圆形至梭形，中等量不明确的蓝色至细空泡状细胞质，以及散在间质碎片的局灶性条纹伪影。组织病理学检查显示恶性肿瘤由椭圆形至梭形核组成，嵌入可变的透明质基质中。免疫组化显示，肿瘤细胞结蛋白和肌细胞生成素呈阳性。提供了梭形细胞/硬化性 RMS 的诊断。本研究构成了两个罕见的梭形细胞/硬化性 RMS 病例的细胞形态学特征的第一个文件。