Photodiagnosis for frameless stereotactic biopsy of brain tumor

Stereotactic biopsy is a minimally invasive method of reaching a pathological diagnosis. However, it is not always possible with this method to obtain the tissue samples required for an exact pathological diagnosis. The factors that can make histological diagnoses uncertain are the heterogeneity of tumors and/or brain shifts in the case of small tumors. In this study, we investigated the usefulness of fluorescence in determining the existence of tumor components in obtained tissues. Six patients underwent stereotactic biopsy. 5-Aminolevulinic acid (5-ALA) was administered orally prior to operation. Frameless stereotactic biopsies were performed. The obtained samples were irradiated with 405nm light and all samples showed red light excitation. Intraoperative rapid pathological diagnosis was made in each case by microscopic examination of frozen section samples. The final pathological diagnoses were of three glioblastomas, one astrocytoma grade 3, and two malignant lymphomas. One case was initially thought to be gliosis on rapid pathological diagnosis, but the final pathological diagnosis reached by examination of a permanent HE stained section was astrocytoma grade 3. Another case, finally diagnosed as malignant lymphoma, was initially diagnosed as infiltration of lymphocytes. The discrepancies between rapid and permanent pathological diagnoses might be caused by the destruction of cells. 5-ALA photodynamic diagnosis is not influenced by the destruction of tissues, simply because it does not depend on the structure of tissues. Stereotactic fluorescence biopsy is very useful in that it enables rapid and exact biopsy and obviates the necessity of waiting for an intraoperative report from a pathologist.