Extra-cranial metastasis of glioblastoma multiforme presenting as acute parotitis

We present an unusual case of extracranial metastasis of glioblastoma multiforme (GBM) to the parotid gland and cervical lymph nodes. The patient had previously undergone two craniotomies to debulk a left frontal GBM, followed by radiotherapy. After the second craniotomy, while waiting for chemotherapy, the patient was re-admitted with a short history of a painful swelling of his left parotid gland. The initial diagnosis was infective parotitis; however, as there was no improvement with broad-spectrum antibiotics, CT was undertaken, which revealed a mass in the parotid gland with a necrotic centre and enlarged cervical lymph nodes. Parotid gland biopsy revealed a parotid GBM metastasis. This case illustrates how GBM behaves in an aggressive manner even outside the CNS. A brief review of the literature and of the theories, which might explain the extra-neural metastasis of this tumour is also presented.