Answer: 2nd branchial cleft cyst

You always have to think of malignancy, but in a younger patient, this is a good option. Oh yeah, and this patient presented with more acute pain, swelling, redness - so yep, it was infected as well.

reference: https://radiopaedia.org/articles/second-branchial-cleft-cyst and http://learningradiology.com/archives2010/COW%20388-Branchial%20cleft%20cyst/branchialcleftcorrect.htm