An Extracranial Metastasis of Glioblastoma Mimicking Mucoepidermoid Carcinoma

BACKGROUND: Glioblastoma (GBM) is the most common and aggressive primary malignant tumor of the brain and central nervous system. Extracranial metastases of GBM are rare, with few case reports published to date. The tumor cells of GBM show strong immunopositivity for glial fibrillary acid protein. CASE DESCRIPTION: A 47-year-old man without comorbidities presented with a 1-year history of an augmenting right parotid lump. A right total parotidectomy with selective neck dissection was performed. The hematoxyline eosin-stained slice of a parotid lymph node collected intraoperatively revealed destruction of normal lymph node structure by medium-sized pleomorphic cells scattered in groups; their cytoplasm was lightly stained and pale. There were abundant myxoid stroma in the interstitial tissue. This characteristic mimicked mucoepidermoid carcinoma. An immunohistochemistry test demonstrated that the tumor cells were positive for glial fibrillary acid protein. A diagnosis of extracranial metastasis of GBM was made after confirmation with postoperative pathologic examination and the review of the intracranial resection specimen. CONCLUSIONS: We believe that this is the first reported case of extracranial metastasis of GBM resembling mucoepidermoid carcinoma in the microscope features. Pathologists and clinicians should be alert to this rare lesion and consider this differential diagnosis after excluding other common parotid lesions.