*2.2. Samples*

A total of 35 pheochromocytomas plus 40 control tissues (20 sections from the heart and 20 sections from normal adrenal glands) were obtained from para ffin-embedded tissue blocks in the College of Veterinary Medicine Anatomic Pathology, University of Florida tissue archive. Representative sections of each tumor were evaluated by a board-certified veterinary pathologist (MJD) to confirm the diagnosis. Clinical records from all samples from patients of the UF Veterinary Medical Center were analyzed to determine mass size and invasion.
