Concomitant multiple myeloma and probable phaeochromocytoma in a cat

Cervone, Mario

biological behaviour, whereas adrenal medullary tumours are called phaeochromocytomas. 9 Furthermore, adrenal tumours may be functionally active, secreting inappropriate amounts of one or more hormones and causing tumour-related syndromes (eg, hyperadrenocorticism or hyperaldosteronism). In contrast, a variety of vague and non-specific clinical signs attributed to excessive secretion of catecholamines have been reported in patients with phaeochromocytomas. 4, 9, 10 In the current case, a hormone-secreting cortical adrenal neoplasia was ruled out on the basis of normal low-dose dexamethasone suppression tests and several normal serum potassium concentrations. Furthermore, a medullary origin of the adrenal lesion was suspected on the basis of the cytological results of FNA. In the examined cat, the suspicion of phaeochromocytoma was strongly supported by the cytology of the mass. A recent study demonstrated that cytology in the characterisation of a primary adrenal mass is useful in discriminating cortical from medullary tumours and it may represent a rapid and easy method to correctly diagnose an adrenal tumour. 8 However, the risk of complications associated with FNA of an adrenal tumour should be considered. Indeed, potential severe and even fatal side effects (eg, pain, uncontrolled haemorrhage or severe hypertensive crisis) could arise from the sudden release of catecholamines, especially during FNA of phaeocromocytomas. 8 MM is a rare multifocal plasma cell neoplasm involving bone marrow, with an estimated incidence of <1% of all feline haematopoietic neoplasms. 11 It is the most common cause of M-proteins, but other conditions can occasionally induce a monoclonal gammopathy in cats, such as chronic infection (leishmaniosis, ehrlichiosis, chronic pyoderma, feline infectious peritonitis), amyloidosis, B-cell lymphoma, Waldenström's macroglobulinaemia, monoclonal gammopathy of undetermined significance and bronchial carcinoma. 11, 12 In the present cat, a diagnosis of a concomitant infectious disease was ruled out, as well as the presence of a primary or paraneoplastic monoclonal gammopathy. Furthermore, current published recommendations for determining a diagnosis of MM in animals require two of the following four criteria: (1) bone marrow plasmacytosis, (2) monoclonal gammopathy based on serum protein electrophoresis, (3) osteolysis and (4) light-chain (Bence-Jones) proteinuria. 12 The cat examined herein met two (bone marrow plasmacytosis and monoclonal gammopathy) of these criteria. Moreover, of the 27 published feline myeloma cases with immunoelectrophoresis results, 22 had IgG gammopathies, as described in the cat in the present report. 11, 13 In humans and dogs, an association between the presence of an adrenal phaeochromocytoma and concurrent neoplasia has been reported. 8 Concurrent neoplasia was found in >50% of the canine phaeochromocytoma cases in two large retrospective studies. 14, 15 Interestingly, an association between MM and adrenal phaeochromocytoma has been previously reported in a jaguar (Panthera onca), associated with a cortical adenocarcinoma in the same gland. 16 A phaeochromocytoma can produce a variety of biologically active neuropeptides and hormones other than catecholamines. In recent years, increasing evidence indicates that this tumour also secretes cytokines, mainly IL-1, IL-6, tumour necrosis factor-alpha and interferon-γ. 2 IL-6 is a pleiotropic cytokine, originally cloned as a B-cell stimulatory fac