The rarer variant of abdominal_bulge where you can see whatever's penetrating a character through their chest.
Because never mind the bones and organs, furries don't work that way. Or said furry is giving birth to a chestburster? Who really knows why! This is usually caused by the following:

• A large penis, tentacle, or object penetrating a character.
• impalement
• knot_bulge
• penis_shaped_bulge
• A xenomorph doing what xenomorphs do.

See also:

• cheek_bulge
• fondling_internal_bulge
• neck_bulge
• abdominal_bulge