I have a hard, fixed lymph node in my groin with history of papillary thyroid cancer. any reason for concern?

Not related?: Unusual for thyroid ca to appear alone in this area. Although anything is possible. I would suggest that you see your doctor.

Should Get Checked: If this lymph node has been present for any length of time, say well over 3 wks and has been growing steadily with no signs of any infection in groin / genital area then definitely should be checked by your doctor.