Eyden Brian
Department of Histopathology, The Christie NHS Foundation Trust, Manchester, United Kingdom.
Ultrastruct Pathol. 2010 Feb;34(1):42-7. doi: 10.3109/01913120903353795.
Rhabdomyosarcoma has traditionally been subclassified into alveolar, embryonal, and pleomorphic variants. Less commonly, spindle-cell, neuroendocrine, sclerosing, and lipid-rich or clear-cell subtypes are seen. The author recently encountered a myogenic sarcoma, with all the common markers of rhabdomyosarcoma, but expressing the unusual features of alpha-smooth-muscle actin and abundant rough endoplasmic reticulum (rER). This myogenic sarcoma, therefore, exhibited four lines of differentiation, and is documented here. The patient was a 65-year-old man with an inguinal soft tissue mass. Following surgical excision, the patient was given radiotherapy and was well without disease after 6 years. The tumor was positive for vimentin, desmin, alpha-smooth-muscle actin, alpha-sarcomeric actin, myogenin, MyoD1, and CD68. Cytoplasm was dominated by abundant rER intermingled with lipid droplets and lysosomes. Cell surfaces exhibited microvillous processes and focal adhesions, but no lamina. Subplasmalemmal smooth-muscle-type myofilaments with focal densities and rare sarcomeric filaments were seen. The low level of expression of some markers was interpreted as consistent with a poorly differentiated tumor. Given the four lines of differentiation--striated muscle, smooth muscle, fibroblastic, and histiocytic--a name reflecting its phenotype would be pleomorphic rhabdomyosarcoma showing smooth-muscle and fibrohistiocytic differentiation.
横纹肌肉瘤传统上被细分为肺泡型、胚胎型和多形性变体。较少见的有梭形细胞、神经内分泌、硬化性以及富含脂质或透明细胞亚型。作者最近遇到一例肌源性肉瘤，具有横纹肌肉瘤的所有常见标志物，但表现出α-平滑肌肌动蛋白和丰富粗面内质网（rER）的异常特征。因此，该肌源性肉瘤表现出四种分化谱系，在此进行记录。患者为一名65岁男性，腹股沟有软组织肿块。手术切除后，患者接受了放疗，6年后无疾病且状况良好。肿瘤波形蛋白、结蛋白、α-平滑肌肌动蛋白、α-肌动蛋白、肌细胞生成素、MyoD1和CD68呈阳性。细胞质以丰富的粗面内质网为主，夹杂着脂滴和溶酶体。细胞表面有微绒毛突起和粘着斑，但无基膜。可见有局灶性致密区的亚膜下平滑肌型肌丝和罕见的肌节丝。一些标志物的低表达被解释为与低分化肿瘤一致。鉴于其有横纹肌、平滑肌、成纤维细胞和组织细胞四种分化谱系，一个反映其表型的名称应为显示平滑肌和纤维组织细胞分化的多形性横纹肌肉瘤。
