Serendipitous discovery of enlarged lymph node in nf1 sufferer by pet - removal/biopsy planned. should i be worried or is this likely to be benign nf?

Removal is better : Lymph mode needle biopsies are sometimes difficult to interpret thoroughly. If an excision of the node is possible, that may be a better option. That way the pathologist reviewing your case will be able to asses the complete nodal architecture. The only worry to have at this point is getting the best sample possible to correlate with the pet.