Concomitant multiple myeloma and probable phaeochromocytoma in a cat

Cervone, Mario

The purpose of this case report is to document probable phaeochromocytoma and MM in a cat. Phaeochromocytomas are extremely rare tumours in domestic animals and to the best of the author's knowledge only eight cases of feline phaeochromocytoma are reported in the peer-reviewed literature. [5] [6] [7] Phaeochromocytomas are often malignant neoplasias, with a median survival time of 20 weeks. 7 Clinical signs are secondary to catecholamine-induced hypertension or due to the presence of a space-occupying mass, and include weakness, collapse, open-mouth breathing, muscle tremors, restlessness, and polydipsia and polyuria. 5, 7 However, hypertension is not always demonstrated as catecholamine secretions may be paroxysmal. 7 Given the vague signs of phaeochromocytoma, an ante-mortem diagnosis is a clinical challenge. Furthermore, routine haematology, biochemistry and urinalysis are non-specific. 6 In humans, biological diagnosis of a phaeochromocytoma is based on documenting abnormal regulation of catecholamines. 6 Thus, one of the initial tests performed in human medicine is direct measurement of catecholamines (eg, epinephrine) or catecholamine breakdown products (eg, metanephrines or urine vanillylmandelic acid) in the blood or urine via high-performance liquid chromatography. In veterinary medicine, a prospective study investigated plasma free metanephrine and normetanephrine levels in healthy cats, cats with non-adrenal disease and in a cat with a suspected phaeochromocytoma, demonstrating an elevated normetanephrine level in the latter. 5 However, a normetanephrine cut-off level to diagnose phaeochromocytoma in cats has not yet been developed and tests for phaeochromocytomas are not commercially available in veterinary medicine. 6 Nuclear imaging via nuclear scintigraphy or positron emission tomography can also be performed to achieve a preoperative diagnosis of phaeochromocytoma. Nuclear combines functional activity with anatomical localisation, allowing identification of the presence of metastasis and multifocal disease. 6 Unfortunately, this technique is not easily available in veterinary patients, and in this case the owner declined referral to a specialist centre in Paris (France). Finally, the catecholamine suppression test can also be performed in humans to diagnose phaeochromocytoma, but this test lacks sensitivity and specificity and has not been previously evaluated in domestic animals. 6 Diagnosis of a phaeochromocytoma in animals requires demonstration of an adrenal mass. This is typically achieved with radiography, ultrasonography, CT or MRI. 6 Abdominal ultrasonography is recommended as part of the staging process in cats suspected of having a phaeochromocytoma, but it is neither sensitive nor specific. 5 Indeed, in a retrospective study of 33 feline adrenal masses, only three patients had phaeochromocytomas. 7 In the current case, the diagnosis of adrenal phaeochromocytoma was suspected on the basis of a left adrenal mass at abdominal ultrasonography, associated with a chronic increase in SAP. Because hypertension is present in >70% of cats with an adrenal tumour, 7 further causes of a unilateral adrenal mass were considered in the differential diagnosis of this patient. In companion animals, adrenal tumours may be primary or metastatic, and arise from different areas of the adrenal gland. 8 Primary neoplastic proliferations of the adrenal cortex are classified as adrenal adenoma and adrenal carcinoma, depending on their