That is a creature from an episode of X-files from like 10+ years ago. Somehow toxic waste caused , wait for it, FLATWORMS, to mutate into that creature. And it was prowling in some sewer system. The episode opened up by some sewer worker getting attacked by something massive while working down there. His body was found later with a large bite/suction mark on his back with 4 ****g-like indentations (see the 4 fangs?). During the autopsy, Scully discovered a live flatworm within his lower abdomen.
Freaky episode, I remember it well. Just not the name.