my education is on the imaging side not the medical side but I believe this: https://www.mayoclinic.org/diseases-conditions/neuroendocrin... + this: https://emedicine.medscape.com/article/176036-overview?form=... - looks like it was shot with this: https://vet-trade.eu/enteroscope/218-olympus-enteroscope-sif...

There's one of those Taboola type ads going around with a similar image that suggests it is a close up of belly fat. Given the source and their propensity for using images unrelated to topic, so not sure if that's what it really is.

Inside of a stomach basically. A polypoid lesion, which I can't tell apart the exact diagnosis but the filename suggests is a neuroendocrine tumor.