Is it a glioblastoma? In dubio pro 5-ALA!

BACKGROUND: Differential diagnosis of unclear contrast-enhancing cerebral lesions includes cerebral metastases as well as malignant glioma. In the majority of cases, a definite preoperative diagnosis by neuroradiological assessment alone cannot be made. Since the introduction of 5-ALA-induced fluorescence-guided resection in the treatment of glioblastoma (GBM), the preoperative putative diagnosis of metastasis vs. GBM triggers a specific preoperative preparation of the patients. We analyzed the patient population with known cancer outside the central nervous system who underwent surgery for an assumed cerebral metastasis and for whom the intraoperative diagnosis was corrected to a malignant glioma.
METHODS: Retrospective analysis of patients with a known primary cancer who were operated on for an assumed cerebral metastasis, which turned out to be a GBM. The patients were treated at our center between January 2008 and June 2011.
RESULTS: We identified ten patients who underwent surgery for an assumed cerebral metastasis and for whom the diagnosis was corrected intraoperatively to a malignant glioma by frozen section. The median age was 68 years (41-82 years). The female-to-male ratio was 2:8. In all patients, the final histopathological analysis of the intracerbral tumors revealed a glioblastoma, while the patients suffered from diverse primary carcinomas.
CONCLUSION: A malignant glioma should always be considered as a differential diagnosis of an unclear contrast-enhancing cerebral lesion even for patients with a known malignancy. Furthermore, we make the case for a more liberal indication for 5-ALA.