Concomitant multiple myeloma and probable phaeochromocytoma in a cat

Cervone, Mario

tor, that is overexpressed in response to injury, inflammation and infection. Its role in cancer is complex, and autocrine and paracrine mechanisms are involved, including the promotion of the survival, migration and drug resistance of malignant plasma cells in MM. 12, 17 Experimentally, deregulated expression of the IL-6 gene can trigger polyclonal plasmacytosis resulting in the generation of a malignant monoclonal plasmacytoma in mice. 18 Consistent with this theory, IL-6-deficient mice do not develop plasmacytoma, indicating the critical role played by IL-6 in murine plasmacytomagenesis. 19 In humans, IL-6 is physiologically expressed in the adrenal cortex, but not in the adrenal medulla and a number of clinical cases have reported the presence of IL-6producing adrenal phaeochromocytoma. 2 Ectopic IL-6 production by phaeochromocytomas has been demonstrated by elevated serum levels of IL-6 or by immunohistochemical IL-6 expression on specimens of the resected adrenal tumours. [2] [3] [4] Furthermore, a fall in serum IL-6 levels after adrenalectomy has been reported. 2 According to the finding of infiltrating mature plasma cells in the bone marrow of two human patients suffering an IL-6 producing pheochromocytoma, 18, 20 it was hypothesised that the phaeochromocytoma in the examined cat may have supported the activation and survival of malignant plasmacytosis in bone marrow, via the secretion of IL-6. Moreover, high serum levels of IL-6 is one of the most common causes of drug-resistance in patients suffering from MM, 17 and it may explain the absence of clinical and biological improvement in the present cat after two different treatments for MM. Unfortunately, the serum concentration of IL-6 was not measured in the cat examined herein, and adrenal secretion was not confirmed by immunocytochemistry with feline antibodies against IL-6. The poor adrenal IL-6 secretion in the current case may be due to the inadequate pretreatment of cytological samples, such as a lack of storage at −20°C before immunocytochemistry, as recommended by the manufacturer.