A phospholipid ether analog labeled with iodine I 124, with a potential imaging property upon positron emission tomography (PET). Upon administration, iodine I 124 NM404 selectively accumulates in and is retained within tumor cells for a prolonged period of time due to the decreased activity of a phospholipase D (PLD), most likely isoform 1 of PLD, in tumor cells compared to normal cells. As tumor cells are unable to metabolize and eliminate MN404, tumor cells can be visualized upon PET imaging. In addition, iodine I 124 NM404 may provide a more accurate image of the tumor than imaging with the current standard. PLD is an enzyme found in the cell membrane of normal cells that degrades phospholipids. Check for active clinical trials using this agent.