摘要：

目的 报告1 例成人髓母细胞瘤伴肌原性分化病例，探讨其临床病理学特征，并复习文献，以提高对此类肿瘤的诊断与鉴别诊断能力。方法与结果 女性患者，32 岁，临床表现为反复口角歪斜、面部麻木6 年余。T₁WI 显示小脑蚓部和脑干背侧混杂信号影，并突向第四脑室；增强扫描显示病灶内类圆形强化结节。手术全切除肿瘤。术中见肿瘤位于小脑蚓部，突向第四脑室并侵及脑干。组织学形态，卵圆形核瘤细胞呈片状密集或散在分布，可见“菊形团”样结构，胞质丰富、嗜酸性，胞核偏位、异型性明显，可见核仁或染色质深染，核分裂象易见，伴出血。免疫组织化学染色，肿瘤细胞弥漫性表达整合酶相互作用分子1、突触素、嗜铬素A、人互联蛋白神经元中间丝蛋白α、神经微丝蛋白、巢蛋白、β-联蛋白和P53，部分表达结蛋白、神经元核抗原和S-100 蛋白，不表达胶质纤维酸性蛋白、少突胶质细胞转录因子2、CD99、广谱细胞角蛋白、上皮膜抗原、肌调蛋白1、肌浆蛋白、肌特异性肌动蛋白和平滑肌肌动蛋白，Ki-67 抗原标记指数约为10%。病理诊断：髓母细胞瘤伴肌原性分化（WHOⅣ级）。术后未接受放射治疗或药物化疗，随访9 个月未见肿瘤复发。结论 髓母细胞瘤是一种常见于儿童小脑的恶性侵袭性胚胎性肿瘤。发生于成人的髓母细胞瘤伴肌原性分化病例少见，含原始神经外胚层细胞和横纹肌母细胞成分是其特点，诊断时应注意与中枢神经系统原始神经外胚层肿瘤、非典型畸胎样/横纹肌样肿瘤和横纹肌肉瘤相鉴别。

关键词: 髓母细胞瘤, 肌细胞, 细胞分化, 免疫组织化学, 病理学, 成年人

Abstract:

Objective  To explore the clinicopathological features of adult medulloblastoma with myogenic differentiation and to discuss clinicopathological differentiations from relevant tumors, so as to improve the ability of diagnosing and differentiating this kind of tumor. Methods  The clinical manifestations, imaging, pathological features and immunohistochemical features of one case of adult medulloblastoma with myogenic differentiation were analyzed, and related literatures were reviewed. Results  A 32-year-old female patient presented with repeated distortion of mouth and facial numbness for over 6 years. T₁WI showed a mixed-signal lesion in the cerebellar vermis and dorsal part of brainstem, and protruded toward the fourth ventricle. Enhanced T₁WI showed a round strengthened nodule in the lesion. During operation, it was seen that the tumor arised in cerebellar vermis, projected into the fourth ventricle and invaded brainstem. On microscopy examination, it was found that oval nuclei tumor cells were distributed in sheet or scattered patterns, and neuroblastic rosettes were observed. Abundant and eosinophilic cytoplasm, eccentrically placed and atypical nuclei containing hyperchromatic chromatin or prominent nucleoli in the tumor could be displayed. Mitoses were frequently seen. The tumor also presented with fresh and old hemorrhage in some place. Immunohistochemical staining showed that tumor cells were diffusely positive for integrase interactor 1 (INI1), synaptophysin (Syn), chromogranin A (CgA), human internexin neuronal intermediate filament protein α (INα), neurofilament protein (NF), Nestin (Nes), β-catenin and P53, and partly positive for desmin (Des), neuronal nuclei (NeuN) and S-100 protein (S-100), but negative for glial fibrillary acidic protein (GFAP), oligodendrocyte transcription factor-2 (Olig-2), CD99, pan cytokeratin (PCK), epithelial membrane antigen (EMA), MyoD1, myogenin, muscle-specific actin (MSA) and smooth muscle actin (SMA). Ki-67 labeling index was about 10% . Pathological diagnosis was medulloblastoma with myogenic differentiation (WHO Ⅳ). The patient was not given further treatment including chemotherapy or radiotherapy after surgery. Nine-month follow-up showed no tumor recurrence.  Conclusions  Medulloblastoma is a malignant, invasive embryonal tumor commonly occuring in the cerebellum of children. Medulloblastoma with myogenic differentiation occurs very rarely in adult, which is characterized by containing primitive neuroectodermal and rhabdomyoblastic elements. The diagnosis should be differentiated from central nervous system primitive neuroectodermal tumor (PNET), atypical teratoid/rhabdoid tumor (AT/RT) and rhabdomyosarcoma.

Key words: Medulloblastoma, Muscle cells, Cell differentiation, Immunohistochemistry, Pathology, Adult