One of our horses has a lump just to the left of his withers - it is slightly warm - and if you rub it it moves and crunches like a muscle that is tense initially - then it just is squashy... Horse doesn't like you to press it too much - but massaging it doesn't upset him.
Vet suggested physio - and physio came - gave us a witchhazel spray and said to massage it - which we are doing... He thought probably caused by ill fitting tack... (he had it when he arrived at our place two weeks ago)
Anyone had anything similar? It doesn't seem to be going away?