Myeloma-Related Disorders in Cats Commonly Present as Extramedullary Neoplasms in Contrast to Myeloma in Human Patients: 24 Cases with Clinical Follow-up

Abstract

Background: Myeloma-related disorders (MRD) are rare neoplasms of plasma cells. Published case reports describe a diversity of clinical presentations with confusing terminology and diagnostic criteria as a consequence of the assumption that MRD in cats are analogous to those in dogs or humans. Objective: The aim of the study was to describe clinical, clinicopathologic and imaging findings, response to treatment, survival and possible associations with other diseases or vaccination in a large case series. A priori hypotheses were that cats with MRD commonly present with extramedullary involvement and uncommonly have radiographic bone lesions, in contrast to human patients. Animals: Twenty-four cats with MRD confirmed by cytology or histopathology and immunohistochemistry. Method: A multicenter retrospective study was performed. Results: Two types of clinical presentation were observed. The first group (n 5 17) had neoplasia involving abdominal organs, bone marrow, or both. All developed systemic clinical signs and paraproteinemia. Five of 7 cats that received chemotherapy improved clinically or had decreased serum globulin concentration (median survival, 12.3 months; range, 8.5-22 months). The second group comprised 7 cats with skin masses, 2 of which were paraproteinemic and developed rapidly worsening systemic signs. In cats without systemic signs, excision of the skin masses appeared to be associated with prolonged survival (up to 2.4 years). Cats with MRD commonly presented with extramedullary involvement (67%), versus humans with MRD (5%) (P , .001), and uncommonly presented with radiographic bone lesions (8%) versus humans with MRD (80%) (P , .001). Conclusions: Radiographic bone lesions are uncommon in cats with MRD and extramedullary presentation is common, relative to human myeloma.

Erythrophagocytic multiple myeloma in a cat

“…24 However, in a recent review of 24 myeloma-related disorders in cats, over 40% of cats with noncutaneous extramedullary plasmacytomas (internal organ involvement) had bone marrow infiltration by neoplastic plasma cells. 25 In contrast, we are aware of only 1 report of a cat with cutaneous extramedullary plasmacytoma progressing to multiple myeloma. 26 The incidence of solitary osseous plasmacytomas progressing to multiple myeloma in cats is unclear.…”

“…1,23,25,27 In the study reporting 8%, not all cats had complete skeletal surveys so it is possible osteolytic lesions were missed and the incidence was actually higher. 25 At the other end of the spectrum was a retrospective study indicating 67% of the cats with multiple myeloma had osteolytic bone lesions. However, the study was performed at an orthopedic referral center with the potential for case selection bias toward cats with clinical signs associated with osteolysis.…”

“…The same study reported cats with either abdominal or bone marrow involvement, or both, that were not treated or were given steroids only, declined rapidly with a median survival time of only 5 days. 25 Because multiple myeloma with erythrophagocytosis is rare in humans, it is unknown if there is a shorter median survival time compared with patients with multiple myeloma alone. It is unclear what, if any, effect the erythrophagocytic component of the multiple myeloma had on the severe clinical course, lack of response to chemotherapy, and short survival of this cat.…”

Intraocular ALλ amyloidoma with plasma cell neoplasia in a cat

“…9 A recent retrospective study found that unlike in human and canine myeloma cases, cats commonly have extramedullary involvement at initial presentation while radiographically detectable bone lesions are absent. 10 Regarding cell morphology, plasma cell tumors are fairly constant and most of them are found in the skin with the digestive tract being the second most common location. 11 Intraocular occurrence of noncutaneous extramedullary plasmacytomas is extremely rare and most human cases have been described in association with multiple myeloma, 12 while only one case involving the uveal tract has been described in the cat, however, without an associated amyloid.…”

Myeloma-related disorder with leukaemic progression in a cat

“…1,2 However, MM and advanced extramedullary plasmacytoma cannot always be distinguished by these criteria; therefore, the diagnostic criteria for MM in cats remain controversial. 3e5 Recently, Mellor et al proposed an all-encompassing term 'myeloma-related disorders (MRD)' for neoplasms of plasma cell origin in cats, and indicated that cats with MRD commonly had extramedullary involvement at the initial clinical presentation 6 while human patients with the MM did not. 7,8 In the present report, we describe a feline case of MRD showing a progressive increase in the number of atypical plasma cells in the peripheral blood.…”