Expression of transgenic GFP/TK in a pituitary adenoma. The main panel shows the green fluorescence of transduced cells around the entry point (arrow) of the needle used to stereotaxically deliver RAd-GFP/TK into the tumor Obj. ×20. The inset shows a low magnification view of the same pituitary adenoma where an entry point of the needle can be seen (arrow). No structural damage is evident as a consequence of the injection. Obj. ×4.