Breathing prob

Question
My Lab has a soft ball size (ba- nine) tumor on his chest.
He has been fine for a long time. Now when he gets worked up. The breathing is short and wheezing. He has to sit and rest. because of lack of breath.
Home and relaxed he is fine.
I think the tumor is blocking his lungs from expanding. what do you think. also Sam is 12 years old and active n happy.

Answer
I would talk it over with your vet.  it is has grown to where it is interfering with his breathing, it is time to remove it as long as he is in otherwise good shape.  Another reason to check with the vet is the breathing could be something unrelated to the tumor.