What are these vein like lines under boob? (photos)

Thank you for your question.  Based on your submitted photos and stated symptoms, you appear to have what is known as Mondor's cords.  The first thing  to do would be to notify your plastic surgeon, as they may have their own set of instructions for how to rememdy the issue. In our practice we advise our patients to massage the cords, apply warm compresses and take NSAIDS like ibuprofen, to resolve the issue.Best regards,Dr. Lane F. Smith, MDPlastic SurgeonLas Vegas, NV

What you are seeing and feeling and inflamed veins.  They are sometimes called Mondor's Cords.  They should go away over time and you should not worry about them.  I recommend that my patients use a warm compress on the area.  Gentle massage and anti-inflammatory medication may help as well.  You should always check with your surgeon first before trying any of these treatments.

This is normal. Don't freak out. It's fairly common. These are inflamed veins which usually appear about three weeks after surgery and often disappear around the sixth week. My patients describe them as guitar strings and they notice them most when they are reaching upward. I often give my patients an anti-inflammatory for discomfort if they can tolerate this medicine.

All the previous experts have given you the correct diagnosis and treatment options. What is concerning to me is why you have NOT seen your chosen surgeon to dx this post op issue??? 

This appears to be much like Mondor's Cords.  Thrombosed veins that can cause discomfort and be visible or palpable.  Warm packs, and NSAIDs are the treatment.  Make sure you let your surgeon know as well.