Golf ball sized growth in stomach

[chelsbells]

DDog had a minor stroke this morning (he's got high blood pressure which was diagnosed last September and he's on meds for that) so we went to the vets for him to be checked over, they kept him in for obs for a couple of hours and he was fine, ate food, was running about, all fine and vet thinks it was just minor and no lasting damage. Great.

However while examining him he said he could feel a fluid like mass, the size of a golf ball on his stomach and wants him in on Monday morning for an ultrasound scan.

Is it most likely going to be cancer? Is the fact he thinks it's fluid better or worse? I need to prepare myself for Monday, I'm always a wreak with bad news so if anyone has some positive experiences or can say what it's likely to be that might help!