mediastinal lymph nodes

I just finished treatment for a recurrence of OvCa.  There is no sign of more OvCa in my pelvis/abdomen and my CA125 is low.  But, during tx, my mediastinal lymph nodes got enlarged (during tx 4-6).  A PET scan indicated "somewhat suspicious" activity.  My gyn onc said it could be the ovca or secondary cancer but for now we will "watch and wait".  Another scan will be repeated in 2 mths.  I am so worried but don't know what worries me most--my OvCa is resistant to my chemo OR it's another type of cancer.  Each search I do about  mediastinal nodes, points in the direction of lymphoma.  I currently don't have any other signs of this, except for night sweating, but my house is warm and I've had it for years.  I have also  had 2 dizzy spells in the past 2 mths, but have also had them prior to my cancer dx, so don't think the node stuff and dizziness are related.   If you had mediastinal  node involvement, how was your cancer found and diagnosed? I am so glad I am going back to work to take my mind off of thinking about this! Cindi