That almost looks more like some kind of damage, as if maybe something fell on it? Or even cold damage which can happen if it's too close to a window in the winter, or if air conditioning is blowing on it. If it is scale, you'll be able to see them - but they're well disguised, and look like a corky bit of bark. If you can figure out that it has scale, isolate it right now! The adults are stationary, but the juveniles are called crawlers, because that's what they do, and they like to travel. Make sure you wash your hands after handling them, to avoid transferring them (this goes for any problem, not just scale). I would try and pick them off with a toothpick, and squish them. I would hesitate to use any kind of insecticide on them, especially your Euphorbia.
