Adult medulloblastoma with myogenic differentiation

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.

DOI: 10.3969/j.issn.1672-6731.2015.09.009