纵隔原始神经外胚层肿瘤伴横纹肌样表型临床病理分析

Clinicopathological analysis of mediastinal primitive neuroectodermal tumor with a rhabdoid phenotype

目的探讨原始神经外胚层肿瘤伴横纹肌样表型的病理特征。方法对1例50岁女性患者的纵隔巨大肿瘤进行光镜、免疫组化及电镜观察。结果肿瘤大小为15 cm×15 cm×16 cm。组织学显示肿瘤细胞小圆形,部分细胞核偏位,胞质内见嗜酸性包涵体。组织化学染色PAS小灶性(+)。免疫组化:vimentin、CD99及chromogranin强(+),S-100蛋白(+),EMA小灶性(+),desmin及MyoD1(-)。超微结构:小圆形肿瘤细胞胞质有短钝突起,见原始细胞连接、发育不良桥粒及胞质内致密核心颗粒。一些肿瘤细胞见核旁分布的、呈旋涡状排列的球形微丝小体,线粒体、粗面内质网及脂滴被包裹在其中。结论原始神经外胚层肿瘤伴横纹肌样表型的病理诊断依赖于光镜、免疫组化及电镜检查。

Objective To study the pathologic characteristics of primitive neuroectodermal tumor with a rhabdoid phenotype. Methods A 50-year-old woman presented with a mediastinal large mass. The specimens were examined by light microscopy, immunohistochemistry, and electron microscopy. Results The size of tumor was 15 cm× 15 cm× 16 cm. Histologically, the tumor was composed of small round cells. The some of the tumor cells had eccentric nuclei and acidophilic intracytoplasmic inclusions. Histochemical staining showed PAS focally positive. The tumor cells were strongly immunoreactive for vimentin, CD99, and chromogranin, positive for S-100 protein, focally positive for EMA, but negative for desmin and MyoD1. The ultrastructural observation indicated that the tumor cells were small round shaped with shorter cytoplasmic processes. The original cell junctions, poorly developed desmosomes, and intracytoplasmic dense-core granules were seen. Some tumor cells were found paranuclear distributed whorl of globular filamentous bodies containing entrapped mitochondria, rough endoplasmic reticulum, and lipid. Conclusion The pathologic diagnosis of primitive neuroectodermal tumor with a rhabdoid phenotype depends on light microscopic, immunohistochemical, and electron microscopic findings.