IgM kappa monoclonal band found in blood

[CosmicHorizon]

I've had a painless lump on my neck for the past 5 and a half weeks. I had an ultrasound scan, and the provisional conclusion was that it is a branchial cleft cyst. However, I also had a blood test and my GP just rang me today and said there is an abnormality in my blood test results. My patient notes say:  "Immunofixation shows the presence of an IgM kappa monoclonal band".

Is this of extreme concern? I'm now thinking that the lump is a swollen lymph node and is indicative of lymphoma?

BTW, 5 days before I first noticed the lump, I had been shaving my neck with a number one razor (which I never do, usually), and I reckoned at the time it was caused by this. But now I'm freaking out that I have cancer.

[Ken_PA]

Your chances of this being some rare immune-system reaction that is not-cancer are increased if you've also had odd, mystery conditions in life.

[Ken_PA]

"Is this of extreme concern?"
Not extreme, no. It's not automatically a cancer. But altogether this is very odd and it needs to be completely investigated. I assume you'll have a surgical biopsy wherein the entire neck node is cut out and examined by a pathologist. It turns out to be lucky that you cut yourself, because that ended up revealing that some kind of underlying condition is present.

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Of all the possibilities, what seems most likely is that you have some type of 'lymphoproliferative disorder'. The nick on your neck would usually create a normal immune system reaction like an enlarged node, but you instead had a very unusual reaction: probably a lymph node changed drastically, now looking like a pocket of fluid (cyst).

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"Immunofixation shows the presence of an IgM kappa monoclonal band"
That's an advanced test. But it does not point to lymphoma. The best diagnosis can be something called MGUS. Or else something really really rare, even some ultra rare reaction to infection. A cancer is not the most likely cause, and also you don't seem to have the symptoms of any cancer such as Multiple Myeloma. Also, in your ultrasound, the Doppler portion didn't show signs of cancer.

"monoclonal" is the key alarm-word there, but it still can be cancer or be not-cancer.

Of great note: the cystic-looking node on one hand and the  'IgM kappa monoclonal band' on the other do not really go together. So the docs must be somewhat mystified. The biopsy should tell, unless the node/cyst is in a dangerous place to do surgery. In that case, they'd want a needle biopsy instead, which draws out fluid and cells to examine and is much less risky.

Let me know how it turns out.