da Silva Leite JG, Nogueira JF, Pallanch J, et al. - Researchers performed an anatomical and radiological analysis to identify a valid anatomical marker that can be used during endoscopic surgery to locate the maxillary sinus natural ostium (MSNO), even if the uncinate process is preserved. In 57 heads of a cadaver (114 sides), dissections are performed. Additionally, a three-dimensional (3D) reconstruction computer program was used to examine 73 CT scans (146 sides) of patients with chronic inflammatory sinonasal disease. At CT 3D reconstruction, the "M" line crossed the MSNO in 112 dissected sides (98.2%) and 140 sides (95.9%). For anticipating MSNO location, the "M" line is a reliable anatomical landmark. It could also improve and promote endoscopic sinus surgery, using traditional, minimally invasive or uncinate preserving techniques.