Swollen groin lymphnode ...13 yr old girl

[Lizzyliz628]

She is 13. All blood tests are normal.  Her right groin area is HUGE.  STILL growing, noticed it begininng of December 2018.  Have a follow up on the 24th of january.  Still very nervous because of the size.  They tested her for EVERYTHING.  all tests are normal.
Any ideas?  Did have mono 3 years ago.

Thanks

[Ken_PA]

Hi, what did her ultrasound say?

Is it possible that it's just fluid (such as a cyst or some very rare spontaneous lymphocoele)? How big is 'huge', more than two inches?