Histopathologic, Immunohistochemical, and Cytologic Analysis of Feline Myeloma-Related Disorders: Further Evidence for Primary Extramedullary Development in the Cat

Abstract

Abstract. Feline myeloma-related disorders (MRD) are rare neoplasms of plasma cells. The multistep transformation model of myeloma in humans is based on the premise that plasma cells undergo neoplastic transformation primarily within the intramedullary compartment and that over time they become poorly differentiated and metastasize to extramedullary locations. Historically, diagnostic criteria used for human multiple myeloma have been applied to the cat, with the assumption that feline MRD commonly arises in the intramedullary compartment. Our objectives were to describe the features of feline MRD confirmed by cytology, histopathology, histochemistry, and immunohistochemistry and to categorize these tumors. A priori hypotheses were 1) tumor category predicts survival and 2) cats with well-differentiated tumors commonly have extramedullary involvement in contrast to human myeloma patients. This multicenter, retrospective study identified 26 MRD cases. There was good agreement between histopathologic and cytologic tumor categorization. Histochemistry and immunohistochemistry were shown to be valuable adjunct tests in the diagnosis of MRD. Cats with well-differentiated tumors had increased median survival relative to those with poorly differentiated tumors (254 versus 14 days). We have reported that marked extramedullary involvement at initial clinical presentation is significantly more common in the cat than in human MRD patients. In this study, we demonstrate that cats with welldifferentiated tumors more commonly have extramedullary involvement than human myeloma patients with well-differentiated tumors (90% versus 20%, P , 0.0002). These results contrast strongly with the human myeloma model of primary intramedullary neoplastic transformation and suggest that primary extramedullary neoplastic transformation may be more common in feline MRD.

Intraocular ALλ amyloidoma with plasma cell neoplasia in a cat

“…13 Production of monoclonal immunoglobulin heavy and/or light chains is typically seen in plasma cell tumors. The secretion of lambda light chains by the plasma cells in the present case is consistent with other reports 16 as well as is the physiologic distribution of light chains in normal feline plasma cells with lambda chains dominating. 17 In contrast to plasma cell myelomas which are multicentric neoplastic proliferations of plasma cells often originating within the bone marrow, extramedullary plasmacytomas infrequently result in local amyloid deposition.…”

“…In contrast to humans and other domestic animals, cutaneous and noncutaneous extramedullary plasmacytomas in the cat are more often malignant and accompanied by systemic effects. Moreover, those extramedullary tumor sites are a common reason for initial clinical examination in cases of myeloma 16 . Therefore, feline patients with a diagnosis of extramedullary plasmacytoma should be monitored carefully for metastatic disease.…”

Comparison of two melphalan protocols and evaluation of outcome and prognostic factors in multiple myeloma in dogs

“…A diagnosis of MM in dogs typically is made by identification of bone marrow plasmacytosis, myeloma proteins in the serum or urine, and osteolytic lesions . Although visceral organ involvement can aid in the diagnosis of MM in other species, such as in cats, intra‐abdominal infiltration does not occur commonly in dogs, with its frequency and effects on prognosis not previously reported…”

Fine needle aspiration cytology in feline skeletal muscle as a diagnostic tool for extramedullary plasmacytoma

“…However, it is worth mentioning the significant number of papers that did not describe the investigation of these viruses in their cases (Radhakrishnan et al, 2004;Mellor et al, 2007;Mellor et al, 2008). Thus, it is possible that the presence of FeLV in the present report is not directly involved in the development of the neoplasm, although further studies with this focus are necessary.…”