Strong chemicals may be applied as well as surgical excision with or without electrocautery.
Mohs micrographic surgery - In effort to remove fewer healthy cells than he would have to during excision, the doctor cuts out the cancerous cells and then examines the bordering ones with a microscope in order to ensure they are all gone.
Surgery: When traditional non-surgical treatments simply don't work (this is often the case on deep birthmarks, such as hemangiomas, also known as strawberry birthmarks), then a surgical excision is usually the next step.
They can be removed by cryotherapy (freezing), laser or electrocauterization (burning), or surgical excision (cutting).
Continued growth usually requires surgical excision before it reaches the pupil.