I may be wrong, but I don't see cancer or even B12 causes for 'sudden' PN. these seem to be more slowly progressing types.

You indicated in another thread that you haven't had an injury, so compression is likely out of the question and no antibiotics or other medications, so toxic shouldn't be a problem either. I'm still thinking you should be worked up for autoimmune more than cancer testing. Immune mediated PN is typically rapid onset like you've presented with. Have they done any work up for you in this regard?

Do you have any family history of autoimmune disorders?