Like your MD said, it can be cancer.., or something else. There's no sure way to tell what it may be without running additional tests (e.g. ct scan,MRI,biopsy,etc)
I too have a mass on my supraclavicular area (plus other areas). I'm very worried also. I've had it for almost 3 years now.. I've never had any symptoms, but these days I'm starting to hurt alot and get tired often...
Well, I hope all goes well with your brother.
Also, please tell me how it goes, because I'm also wondering what else might cause the lump.