How do doctors differentiate pheochromocytoma vs. Panic?

Test hormone levels. The symptoms of pheochromocytoma are caused by the sudden release of adrenaline and similar hormones from the tumor. They can mimic panic attacks. The best way to detect a pheo is my measuring the levels of the relevant hormones in blood and/or urine.
Lab tests and image. The symptoms are similar between panic attacks and pheochromocytoma. One way to distinguish them is to perform lab or urine tests looking for the excess hormones. If tests are positive, then we proceed with imaging study to find the tumor.