Lymph node question

My daughter was diagnosed stage 3b 5 years ago.  The melanoma was nodular in type and on her right neck (developed in an existing mole).  She had a WLE and SLNB which all showed negative for melanoma in tissue and lymph node.  A month later a lymph node near the area became enlarged and FNA was positive for melanoma.  She had a lymph node disection (26 nodes) and partial removal of the parotid gland on the right side.  Everything was negative except for the one lymph node we already knew about.  She then completed 3 courses of biochemotherapy (so glad they have less brutal adjuvant treatments now).  All of her scans have been completely clear with no areas of concern.  Prior to her 5 year scan she noticed an enlarged lymph node under her chin.  They did the scan and determined the node is 1 mm larger than it was in the most recent scan (6 months ago).  The weird thing is the lymph node changes size throughout the day and from day to day.  I have felt it myself and it was larger in the morning and not palpable in the afternoon.  She is scheduled to have it removed and biopsied but I wondered if this is something anyone else has experienced.