My dad has a large ~3cm round/hard mass in his stomach. His stomach was bleeding, and therefore was really low on potassium, but his blood pressure and everything is back to normal now. However, the doctors just sent a letter saying he needs surgery. I want to know if this is serious. He was in so much pain before, because he lost so much blood. He also had black stool twice, and was vomiting. Also, what is 789.06- ABDMNAL PAIN EPIGASTRIC?