These are patients in whom a benign or malignant tumor was recorded requiring surgery. During that surgery, the surgeon will cut away the tumor as part of the treatment of the disease. In this process, it is important that the tumor is removed correctly and completely. To verify that the correct tissue was completely removed, the tissue is examined microscopically. However, a microscopic analysis takes a relatively long time and the result is not known until a few days after the surgery is completed. If that microscopic analysis should eventually reveal that the tumor was not completely removed, additional treatment is usually necessary. An assessment of the excised tissue during surgery would allow additional tissue to be excised in the same operation if necessary. Thus, in this way, additional treatments can also be avoided. This could lead to shorter treatment time and less emotional strain for the patient, as well as lower costs. To date, however, there are no effective techniques to do this. PositronEmissionTomography (PET) imaging can be used to image the tumor that needs to be excised. To do this, a tracer must be administered through the blood before the operation. This tracer is a slightly radioactive substance that can be detected by the PET camera even at low concentrations. This technique is already routinely used in the hospital to detect cancer or inflammatory tissue in the body. During this study, however, it's not the intention to look at the tumor while it is still in the patient's body, but rather after it has been cut out of the patient's body by the surgeon. To do this, the piece of tissue cut away will be scanned using a specially designed PET-CT scanner. The overall goal of this study is to gain additional knowledge. More specifically, the investigators wish to determine which medical conditions may benefit from high-resolution PET-CT specimen imaging.