Myeloma-related disorders in cats commonly present as extramedullary neoplasms in contrast to myeloma in human patients: 24 cases with clinical follow-up.
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.


METHODS
Twenty-four cats with MRD confirmed by cytology or histopathology and immunohistochemistry.


METHODS
A multicenter retrospective study was performed.


RESULTS
Two types of clinical presentation were observed. The first group (n = 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.
Mellor
Paul J
PJ
Department of Veterinary Medicine, University of Cambridge, Cambridge, UK. p.j.mellor.02@cantab.net
Haugland
Sean
S
Murphy
Sue
S
Smith
Ken C
KC
Holloway
Andrew
A
Archer
Joy
J
Powell
Roger M
RM
Polton
Gerry A
GA
Tasker
Severine
S
McCormick
David
D
Tempest
Michelle E
ME
McNeil
Pauline E
PE
Scase
Timothy J
TJ
Knott
Chris D
CD
Bonfanti
Ugo
U
Villiers
Elizabeth J
EJ
Argyle
David J
DJ
Herrtage
Michael E
ME
Day
Michael J
MJ
D000818:Animals; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000473:pathology; D002371:Cat Diseases / Q000175:diagnosis* / Q000473:pathology; D002415:Cats; D003937:Diagnosis, Differential; D004285:Dogs; D005260:Female; D006801:Humans; D008297:Male; D009101:Multiple Myeloma / Q000175:diagnosis / Q000473:pathology / Q000662:veterinary*; D009928:Organ Specificity; D011859:Radiography; D012189:Retrospective Studies; D023981:Sarcoma, Myeloid / Q000175:diagnosis / Q000473:pathology / Q000662:veterinary*; D013045:Species Specificity; D016019:Survival Analysis