1. An endoscope system processor device, comprising: a receiving unit that receives an image signal obtained by imaging an observation target with an endoscope; an oxygen saturation calculation unit that calculates an oxygen saturation based on the image signal; a pixel specification unit that specifies an out-of-range pixel in which the oxygen saturation deviates from a specific range set in advance; and a diagnostic information calculation unit that calculates diagnostic information as a numerical value using information of the out-of-range pixel.