Cerebral astroblastoma in an adult: An immunohistochemical, ultrastructural and genetic study

Abstract

Astroblastoma is a rare glial tumor of unknown origin, usually affecting the cerebral hemispheres of children and young adults. Here we report an unusual cerebral tumor in a 60-year-old woman. On MRI, the tumor appeared as a well circumscribed lesion in the left frontal lobe. Histopathologically, it was composed of rounded eosinophilic cells, and was divisible into two areas. One area was characterized by a collection of GFAP-positive cells around sclerotic blood vessels (astroblastic pseudorosettes and perivascular hyalinization), and had a Ki-67 labeling index of 2.8%. However, the other area was highly cellular, showing many GFAP-negative cells often with a rhabdoid appearance, mitoses and a Ki-67 index of 15.7%. Thus, a final diagnosis of malignant astroblastoma was made. In both areas of the tumor, nearly all the cells were positive for epithelial membrane antigen, and many were positive for oligodendrocyte transcription factor 2 (Olig2). Focal expression of cytokeratin was also evident. With regard to genetic markers, the tumor cells were positive for INI1 and negative for mutant IDH1. The p53 labeling index was <1%. Ultrastructurally, the presence of intra- and intercellular lumina with microvilli was a feature. DNA examination of IDH1/2 and TP53 showed no mutations. In conclusion, although ependymal features were evident ultrastructurally in the present tumor, the immunohistochemical expression pattern of Olig2 was that of diffuse astrocytoma. On the other hand, the absence of mutations in both IDH1/2 and TP53 suggested that the present tumor was not a purely astrocytic neoplasm. Further studies, including molecular and genetic analyses, will provide insight into the histogenesis of astroblastoma.

A case of cerebral astroblastoma with rhabdoid features: a cytological, histological, and immunohistochemical study

“…Non-palisading necrosis like our case also does not indicate malignancy [12]. IDH1 mutation, reported in gliomas, is recently detectable by immunohistochemistry [21], but IDH1 mutation was absent in this case, which was compatible with previous reports [14,19].…”

“…Although this case was diagnosed as malignant (anaplastic) astroblastoma, the patient had no evidence of tumor recurrence without postoperative radiotherapy or chemotherapy during the last 2 years of follow-up [14]. Another case of astroblastoma with rhabdoid features and favorable long-term outcome has been reported [9].…”

“…Ki-67 index [8]. Fu et al described a case of astroblastoma with two components, typical astroblastic features and unusual rhabdoid appearance [14]. In their case, GFAP-positive cells around sclerotic blood vessels were observed with low Ki-67 labeling index in the typical astroblastic area, whereas the highly cellular area was composed of many GFAP-negative cells often with a rhabdoid appearance with high mitotic activity and Ki-67 labeling index.…”

“…Cytoplasmic immunoreactivity for GFAP, vimentin, and S-100 protein is characteristic for astroblastoma [3,13,14]. EMA expression, especially localized at cytoplasmic margin, is also one of the distinctive features in astroblastoma [13][14][15]. Bonnin and Rubinstein divided astroblastoma into two groups from the aspect of malignancy: low-grade (well differentiated) and high-grade (anaplastic).…”

Crush Cytology of a Primary Intraspinal Rhabdoid Papillary Meningioma: A Case Report

“…Intraoperative frozen diagnosis may sometimes be difficult. Cytologic findings of rhabdoid papillary meningiomas are shared in part with those of spinal cord gliomas and other tumors, such as ependymoma, astrocytoma, astroblastoma and rhabdoid tumors, including atypical teratoid rhabdoid tumor (AT/RT), and even leptomeningeal metastasis of metastatic carcinoma with secondary rhabdoid differentiation [14,23,24,25,26,27,28,29,30,31,32]; therefore, frozen diagnosis of rhabdoid papillary meningioma remains feasible. …”