Several years ago, my very promising 6-year old mare began acting
"studish." After palpation by my vet, she was diagnosed with a HUGE
granulosa cell tumor on her ovary. After surgery to remove it -- turned
out to be the size of a cantalope -- she began bleeding internally. She
had massive trauma from the bleeding, and foundered. Tried to save her for
several months, but ended up having her put down. Needless to say, it was
horrible for me, since I had bred and raised her.
Sorry for bad news, but those tumors are horrible and not to be
messed with. Good Luck!!!!!!!!!