Case Report: Collision Tumor Involving Diffuse Large B-Cell Lymphoma (DLBCL) and Meningioma.

We report on a 73-year-old man, initially diagnosed with testicular stage IE DLBCL and an incidental finding of an extra-axial right frontal mass with MRI features of a convexity meningioma. The DLCBL relapsed <2 years after treatment, with multiple lymphoma localizations and increased uptake in the grown extra-axial meningeal mass on 18 F-FDG PET-CT. CD19-CAR-T therapy induced a complete metabolic response with the exception of the frontal mass. Surgical resection revealed a collision tumor involving DLBCL and meningothelial meningioma. Collision tumors-2 histologically different neoplasms that occupy the same anatomic location-are uncommon, especially those occurring in the central nervous system.