1, border: the edge of ordinary nevus is smooth and clearly demarcated from the surrounding skin, while the edge of malignant melanoma is not neat and jagged. In addition, the surface is rough with scaly or flaky desquamation, sometimes there is oozing liquid or blood, and the lesion is higher than the skin.

2, diameter: the diameter of common nevus is usually less than 5 millimeters, while the diameter of malignant melanoma is more than 5 millimeters.

3, asymmetry (asymmetry): ordinary nevus two halves are symmetrical, while malignant melanoma two halves are not symmetrical.

4, color (color): ordinary moles are usually tan, brown or black, while malignant melanoma will be mixed with pink, white, blue-black on the basis of tan or brown. Among them, blue color is the most ominous, and white color suggests that the tumor has self-degeneration. Nodular malignant melanoma is always blue-black or gray.

5, itchy, painful nevus should also pay special attention to, this kind of nevus if continue to develop is likely to appear ulcerative lesions, stinging or burning pain will be more obvious, its surrounding satellite nodules or accompanied by regional lymph node enlargement, at this time, it shows that the disease has progressed to the advanced stage.

Suggestions:

It should be emphasized that it is very difficult to distinguish a poorly structured nevus from an early malignant melanoma by visual observation alone, and a biopsy of the suspected lesion should be carried out in a timely manner to obtain a definitive diagnosis of the pathology.