In conclusion, considerable progress has been made so far in the development of COX-2 tracers that can be used for the in vivo imaging of the COX-2 enzymes, considering the obstacles met at the beginning, which included low metabolic stability, high blood retention of the sulfonamide analogs due to off-target binding to CA, and off-target binding to p-glycoprotein, which is a nuisance as it decreases the tumor–muscle ratio, and suitability of biological models for the in vivo evaluation of the prospective tracers. Here, PTGS2 is linked to neoplasm.