If a child suddenly has a black spot on his body, the first thing to determine is whether it is accompanied by certain pain. 1. if there is pain, it may be a local bleeding due to trauma, and the bleeding may form a kind of pigmentation after a longer period of time, thus forming the symptom of a black spot. 2. if there is no obvious pain, it may also be a pigmented nevus, because some children will develop pigmented nevi after gradual growth. Another possibility is malignant melanoma, which is a malignant tumor, but some children may have it, but the probability is very low.