gms | German Medical Science

Objective: Contrast enhanced T1-weighted magnetic resonance imaging (MRI) is the gold standard for delineating malignancies of the brain. However, recent studies suggested that even metastatic brain disease can be associated with significant infiltration beyond the area of contrast enhancement. In primary brain tumors, FLAIR (fluid attenuated inversion recovery) hyperintensity is frequently associated with tumor infiltration. However, FLAIR hyperintensity in other malignancies is largely viewed as peritumoral edema. This analysis was carried out with the aim of assessing whether there is an association of perimetastatic FLAIR hyperintensity with the presence of infiltrating tumor cells.

Methods: Patients undergoing surgery for metastatic brain disease as part of the Metastasys study were included in the protocol. Based on preoperative MRI, screenshots were taken using neuro-navigation during surgery. After complete removal of the contrast enhancing tumor and its pseudo-capsule according to neuronavigation and microsurgical feedback, additional samples were taken from the tumor margins and areas with peritumoral FLAIR enhancement. Histological workup with Cytokeratin AE1/AE3 immunostaining for epithelial tumors and Melan-A and HMB 45 for melanomas was used to assess tumor infiltration in the peritumoral specimen by two neuropathologists who were blinded to the origin of the specimen. Using descriptive statistics, we assessed the association of a FLAIR hyper intensity with tumor infiltration.

Results: The present analysis includes 15 patients who underwent a total of 19 tumor resections. NSCLC was the primary malignancy in 6/15 cases (40%). Fifty-two specimens were obtained. Peritumoral FLAIR hyperintensity was positive in about half of the patients (7/15; 47%) and samples (25/52; 48%). NSCLC group showed positive infiltration in (3/6; 50%) cases and (13/23; 57%) specimen.

Conclusion: Based on our data, tumor infiltration is present in about half of peritumoral FLAIR hyperintensity. This finding further corroborates the concept that conventional contrast-enhanced MRI potentially underestimates the extent of tumor and that refinement in imaging is required to allow for more precise preoperative tumor detection in metastatic brain disease.