If a very small mole suddenly grows on the back of the hand, it may be a common pigmented mole or spider nevus. It is recommended to check the type of mole first and choose laser or surgical treatment according to the situation after clear diagnosis. 1. Pigmented nevus: if a very small mole suddenly grows on the back of the hand without pain or itching, and without rapid growth, it is usually a pigmented nevus, which is caused by ultraviolet radiation, skin aging, etc., so there is no need to worry too much about it, and if you think that it affects the aesthetics, you can remove it by laser or surgery. 2. Spider nevus: formed by the expansion of the end branches of small skin arteries, can be seen in normal people or patients with liver disease. It can also lead to the sudden formation of a small mole on the back of the hand. First of all, you need to improve the relevant examination to exclude the factor of liver disease. If this kind of nevus appears in normal people, it can be removed by pulsed dye laser. If a small mole suddenly grows on the back of the left hand, it is recommended to go to a dermatologist for professional diagnosis, and treat the symptoms after a clear diagnosis.