I don't know about electro devices for external tumours but I do know that black salve also known as bloodroot salve and compound X and cansema, works.
I am using it and it is not as painful as I thought. I have not had to use any painkillers.
I bought the salve without the zinc. It is just herbs. Here's where I bought it.
http://www.larsoncenturyranch.com/NC_Salve.html