Spade Female Cocker attracting dog

Question
Our 12 year old cocker spaniel was spade while young.  Just recently our 4 year old nutered male schnoodle smells her tummy and rear and also hump at her.  We have had them together for 4 years and this is the first we see of it. The cocker spaniel also has a medium side lump that our vet has seen - it is on her tummy where he sniffs.  Is he detecting maybe cancer? or do you think this is a dominance thing.  Our cocker spaniel is much more dominant.

Answer
What did your vet do with the lump?  He should have aspirated it and done an analysis.  (Aspirating is just taking a bit of fluid with a very fine needle..doesn't hurt the dog).

At age 12 I wouldn't settle for less than an analysis.  If the vet just looked at it, get a 2nd opinion including bloodwork.

As far as the male suddenly paying attention - I doubt it means anything.