Can anyone answer this?

Hi-Five years ago I had my left breast removed.There were 17 out of 20 cancerous lymphnodes.After chemo and arimedex I was fine for five years. I recently had a petscan and it showed 3 small nodes on my lung (5mm) and also a small area between my lungs and under my arm. My doctor put me on herceptin and is adding xeloda. I went for a second opinion and the doctor asked if my doctor had done a biopsy this time. He hasn't. The new doctor said that we have to know what we're dealing with. Maybe it isn't her2 positive anymore, maybe it isn't breast cancer anymore. Perhaps it's lymphoma or lung cancer. In which case, the herceptin wouldn't be helping at all. My original doctor said he wouldn't want me to have a biopsy because the location would be too hard to get to because it's behind my lung.So his idea was to give me the herceptin and xeloda and test me in 6 weeks to see if I needed taxotere or something stronger. The new guy wants me to see the thoracic surgeon Monday and schedule a biopsy to see what kind of cancer it is.I'm confused about what to do. The new guy thinks I should have had radiation 5 years ago too, which I didn't.What do you think? Are some areas too dangerous to biopsy and what is your opinion about what doctor is right? Thanks so much! I really value your opinions!God Bless you all! Cathy