**5. Conclusions**

Canine pheochromocytomas have similar immunohistochemical characteristics to those previously reported in human tumors, with approximately 82% showing immunohistochemical evidence of an SDH family mutation. However, based on a small number of cases, there does not appear to be a correlation with invasion and SDH family gene mutation status. Further sequencing work is needed to verify the IHC results and to determine the genetic basis of canine pheochromocytoma; a larger pool of cases is also needed to confirm a lack of association between invasion and SDH family mutation status.

**Author Contributions:** Conceptualization, F.M.A. and M.J.D.; methodology, F.M.A., M.A.B., O.A.A.-M., M.J.D.; formal analysis, F.M.A., O.A.A.-M., M.J.D.; investigation, F.M.A., M.A.B., O.A.A.-M., M.J.D.; writing—original draft preparation, F.M.A., M.J.D.; writing—review and editing, F.M.A., M.A.B., O.A.A.-M., M.J.D.; visualization, M.J.D.; supervision, M.J.D. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.
