Malignant intracerebral nerve sheath tumour [MINST] simulating malignant glioma

ABSTRACT

Though schwannomas constitute 8% of all intracranial tumours[5], less than 20 cases of intracerebral schwannomas have been reported so far in world literature.[7] All the rest of schwannomas arise from the cranial nerves. Its malignant counterpart, malignant intracerebral nerve sheath tumour [MJNST] is even rarer. Only six cases of MINST have been reported to date [1] We report a MINST managed by the authors and review the relevant literature. Forty-year-old male patient presented with features of raised intracranial pressure. Cranial magnetic resonance imaging [MRI] revealed a well-defined enhancing parenchymal tumour of right insular region. It was unique in having a hyperintense peripheral rim on T2-weighted images akin to the cerebrospinal fluid cleft. At surgery, the tumour was firm and discrete and it could be shelled out from the surrounding parenchyma. Histopathology revealed a lobular tumour, uniform distribution of vascular spaces lined by plump endothelial cells with rhabdomyoblastic differentiation and cellular component with mitotic figures. Most of tumour cells were positive for vimentin with variable and patchy positively of S-100. Malignant intracerebral nerve sheath tumour is an extremely rare tumor [1] Schwannomas are not known to undergo malignant degeneration and hence, it is preferable to label it MINST [10] However, it can mimick a malignant glioma on radiology, its discrete nature both on the MRI and at surgery remains unique. Lobular nature and rhabdomyoblastic differentiation has been described for the first time. Complete excision followed by irradiation and chemotherapy seems to be most appropriate treatment but the prognosis is still poor [6]