What Causes Tumour Under Clavicle And How Best To Treat It?

My mother (64 years old) had breast cancer in the past, the doctors here in Saudi Arabia has removed both breasts, that second operation that they removed her right breast was almost 9 years ago, she never needs any chemotherapy. she is in very good health, she has noticed 3 weeks ago a tumor under her right clavicle, it looks like part of bones, the doctor insist to remove it first then scan the tumor, he doesn’t want us to take a sample of it first, he says we will remove it any way so it is better to save time, I was wondering what make him sure of the type of this tumor? As the x-ray doctor said that, this tumor could be anything he was not sure of it, am a afraid that we are lost and we don’t want to make a surgery for nothing! What is the best way to identify this “thing” under her clavicle? In addition, usually if this is a cancer, what kind of cancer is that and how we deal with it. Thank you