I wonder if this could be lymphedema?

You need to call your surgeon or whoever is covering for him (do not wait for Monday). There are several serious surgical complications that you could have based on your description. Lymphedema is less likely to show up this quickly than other complications of surgery.

It’s much likelier what you’re experiencing is a seroma in your SNB site. Many if not most of us get them. Nature abhors a vacuum--and when tissue is removed, your body naturally wants to fill the cavity with fluid to protect it as it heals. Almost all of us who’ve had SNBs found those incisions & seromas more sore and annoying than our lumpectomy incisions and any mammary seromas. Try to avoid wearing anything that might irritate it (seams, scratchy lace on bras or nightgowns, etc.). A pillow beneath your arm can help too (our cancer center gives them out--with a velcro shoulder strap attached--to all lumpectomy patients). You can take a throw pillow and sew a strap so you can hang it from your shoulder. By all means see your surgeon, to rule out a hematoma or infection. (And if you have a large breast in danger of pulling the SNB incision open--as mine did, causing the seroma to leak spectacularly, ask if you should have the incision reinforced with sutures, not just steri-strips. Suturing my incision was a dramatic step in helping it heal till the seroma eventually disappeared).

But it’s almost certainly not lymphedema (take it from someone who has LE). The nerve-shock pains are probably from nerves irritated by the shifting of the fluid in the seroma and the impact of each stem transferred upward. And at 2 weeks post-op, it’s not too soon to have pangs and zapping pains from nerves beginning to reconnect.

Sending good thoughts for your surgery, seraphima, let us know how it went, when you get a chance.