If a nevus suddenly increases in size within a short period of time, rapidly forming a raised nodule and deepening in color, it is important to be alert. When the nevus expands to a certain extent, papillary proliferation or rupture occurs, forming a small ulcer (often in the shape of a spit of fire), and the surface bleeds easily, oozes fluid, or is covered with bloody crusts, and black dots, black halos, or pigmented nodules often appear around it. At the same time, the patient feels localized itching, burning and painful discomfort. If these changes occur on the body of a nevus, one should immediately seek medical attention, preferably by taking a biopsy for pathological examination to clarify the diagnosis.