Hi Peng Yuan,
Very sorry to hear that your mother has been diagnosed with melanoma. The treatment options should be discussed with you by your dermatologist. The next steps depend on how deep the melanoma is.
For shallow melanomas less than 0.8mm thick with no ulceration, surgical removal with good margins may be adequate. For deeper melanomas with ulceration, she will require surgical removal of the melanoma and referral to an oncologist for further staging. This refers to investigations to check if there is a spread to the neighbouring lymph nodes or other organs.
In advanced cases, immunotherapy or targeted therapy may be required, and these will be carried out by her oncologist.