Image from the Costco subreddit, where the top comment is that this is "green muscle disease."
"There is no evidence that Green muscle disease is caused by a pathogen, so technically it would be considered safe to consume a bird with it. However, it may not be aesthetically pleasing to eat green meat. The green discoloration of the meat is similar to a bruise that is trying to heal."
Additional information from an AOL webpage:
Green muscle disease — which is also called ischemic myopathy, deep pectoral myopathy, or green breast — is a condition that develops in larger chickens or turkeys when their pectoral muscles are overdeveloped, becoming too large for the blood supply to reach that region. According to the U.S. Department of Agriculture (USDA), when birds use those muscles to repeatedly flap their wings, the exertion causes the muscles to swell, further restricting the blood supply to that area. Without adequate circulation, those muscles die, turning green in the process.
The comparison to a bruise evolving from reddish-blue to green is accurate. The green color arises from the breakdown of hemoglobin or myoglobin in the dead muscle. This is way different from the green color in wounds that arises from the presence of bacteria like Pseudomonas aeruginosa, whose presence should be detectable by a foul and nauseating odor.* So in the case presented, there would be no disease risk in eating the normal parts of that chicken.
This report was sent to me by a pathologist, who commented that "green muscle disease" should be called what it is: necrosis. I'll add a comment to express my dismay about the extent to which our food service industry is now bioengineering fowl. I knew that turkeys were falling over from overdeveloped breasts, but this is the first time I've heard about vascular insufficiency in the poor creatures.
*historical anecdote re Pseudomonas. When I was working the major medicine ER in Parkland Hospital decades ago, a patient was wheeled into a closed examining room suffering from a decubitus ulcer that extended from his shoulders to his coccyx, the entire extent glowing almost neon green from Pseudomonas colonization. A series of nurses went into the room to examine him and prepare him for admission upstairs, and at least two of them exited the room wretching or vomiting. I have always had the deepest possible respect for Parkland ER nurses, who are tough as nails and have seen everything there is to see. The reason these two were retching has nothing to do with squeamishness; the detection of the odor bypasses the cortical analytic processes and goes directly to the brainstem to produce nausea - a vestigial reflex that natural selection employed to protect our earliest ancestors from dangerously contaminated meat.
