Pheochromocytomas are cromafines cells neoplasias of adrenal marrow, they are less common in dogs (0.13-0.01 % of total canine tumors) and extremely weird in cats, they can be functionally active to produce epinephrine and norepinephrine or inactive. Although they are histologically considered benign, if they produce long distance metastasis they also malignant. Because of this tumors don't respond to physiologic mechanisms that regulate catecholamine excretion, pheochromocytomas can do it some with stimulus like blood pressures changes, stress or tumor manipulation.

Clinical findings can be parasitical and vague because of tumor capacity to produce catecholamines or to metastasis different organs.

Of this rare clinical presentation and non specific sinology, most of the times the diagnosis is made by necropsy (27-85% of cases).

The next essay describes a case of a two year old Golden Retriever, that was referred to the UNAM Veterinary Hospital with one week of anorexia, depression and abdominal distension. In the physical examination the patient was depress, has poor body condition, pale mucose, 7% dehidratation and in abdominal cavity a 10 cm diameter tumor was found CBC, serum chemistry profile and urinalyses were performed and non regenerative anemia 0.24L/L, bilirubinemia 6.9 µmol/L arise and increased ALT 268 U/L, AST 286 U/L and creatinine kinase 742 U/L.

Radiographic studies were done abdomen and thorax, peritoneal effusion and right heart size increased was found. Ultrasound was performed and spleen and liver tumor was found.

Necropsy findings were: Adrenal neoplasia with metastasis in liver, spleen, pancreas, heart and regional lymph nodes. The histopathologic diagnosis was compatible with pheochromocytoma, confirmed using grimelius and reticulina stains and finally with the electronic microscopy valuation.

Discussion: In the present essay an adrenal tumor was diagnosed by histopathologic and electronic microscopy as a malignant pheochromocytoma with multiple metastases. Adrenal pheochromocytomas in dogs are usually benign neoplasms that have for local invasion, but they are occasionally malignant with metastasis to distant organs.

The clinical signs of pheochromocytoma can result from either and excess production of catecholamines or by local of the tumor, diagnosis is often difficult and this case highlights the difficulty in this, because the dog did not present with the typical history or clinical description.

Antemortem diagnosis of pheochromocytoma is uncommon and required a high index of suspicion for the clinician.