The sudden growth of a mole on the left hand may be caused by abnormal embryonic differentiation, or it may be caused by external stimulation of the local skin.
Moles generally refer to pigmented nevi, which are benign skin growths. Congenital pigmented nevi are mostly present at birth or appear within a few days after birth. This condition is mainly related to abnormal cell differentiation during the embryonic period.
The cause of nevus pigmentosus is currently unknown, but it is clear that localized skin irritations often lead to nevus pigmentosus. Sun exposure, trauma, chemical irritation, or topical glucocorticoid creams may cause nevus pigmentosus.
Because of frequent contact and friction with the outside world, you need to go to the hospital for regular checkups after growing a mole, and do physical laser or surgical excision if necessary. Pigmented moles under the nails have a higher risk of malignant transformation and need to be treated in a timely manner.