Glioblastoma multiforme in skin: a report of 2 cases and review of the literature.

Despite an aggressive clinical course, glioblastoma multiforme (GBM) rarely develops extracranial metastasis, with only 6 cases of skin involvement reported in the literature. We report 2 cases of GBM that spread to the scalp. Both patients presented with a firm nodule adjacent to their original craniotomy site. Histologic examination revealed highly anaplastic tumor cells invading the subcutaneous tissues. Immunohistochemistry was positive for vimentin, S-100, and glial fibrillary acidic protein in the malignant cells. Although it is possible that these cases represent true metastatic GBM, the close proximity of the nodules to suture lines suggests extension of GBM to the skin through surgical sites or seeding of tumor cells. It is important to have an accurate clinical history when evaluating scalp nodules in patients with GBM, so that a diagnosis of GBM is not overlooked.