Descriptive analysis and prognostic factors in cats with myeloma-related disorders: A multicenter retrospective study of 50 cases

BACKGROUND

Myeloma-related disorders (MRDs) are rare and poorly documented neoplasms of cats.

HYPOTHESIS/OBJECTIVES

To describe clinical, clinicopathologic, and imaging findings, response to treatment, and survival time and to identify factors associated with shorter outcomes in cats with MRD.

ANIMALS

Fifty cats with a diagnosis of MRD.

METHODS

Cats with paraproteinemia confirmed by serum protein electrophoresis (SPE) and either intramedullary plasmacytosis >10%, marked cytonuclear atypia with intramedullary plasmacytosis that ranged between 5% and 10%, or cytologically or histologically confirmed visceral infiltration were retrospectively included from several veterinary referral centers.

RESULTS

Bone marrow plasmacytosis and splenic or hepatic involvement were present in 17/27 cats (63%), 36/42 cats (86%), and 27/38 cats (71%), respectively. Anemia was reported in 33/49 cats (67%) and thrombocytopenia in 16/47 cats (34%). Some of the treatments that the cats received included melphalan and prednisolone (n = 19), cyclophosphamide and prednisolone (n = 10), chlorambucil and prednisolone (n = 4), prednisolone (n = 4), or other (n = 4). The overall response rates to melphalan, cyclophosphamide, and chlorambucil in combination with prednisolone were 87%, 90%, and 100%, respectively. Adverse events to melphalan or cyclophosphamide occurred in 65% and 23% of cats, respectively. Median survival time was 122 days (range, 0-1403) and was not significantly associated with chemotherapy protocol. Anemia (hazard ratio [HR], 3.1; 95% confidence interval [CI], 1.0-9.8) and thrombocytopenia (HR, 2.7; 95% CI, 1.2-6.0) were risk factors for shorter survival.

CONCLUSIONS AND CLINICAL IMPORTANCE

Our study confirmed the guarded prognosis of MRD in cats and identified risk factors for shorter survival times.

Myelomatous pleural effusion in a cat diagnosed with multiple myeloma

Case summary

A 10-year-old male castrated domestic shorthair cat was presented with a 3-day history of dyspnoea, chronic lethargy and inappetence. A bilateral pleural effusion was identified by thoracic ultrasound, and cytological examination revealed numerous atypical plasma cells. Biochemistry and serum protein electrophoresis revealed a severe hyperglobulinaemia associated with a monoclonal gammopathy. A moderate non-regenerative anaemia was also noted. Multiple bone lytic lesions were detected, and marked plasmacytosis was observed on bone marrow aspirates. Chemotherapy with cyclophosphamide and prednisolone was initiated but did not result in any clinical or biological response, and pleural effusion recurred. Lack of therapeutic response led to euthanasia 2 months after diagnosis.

Relevance and novel information

This is the first description of a myelomatous pleural effusion in a cat diagnosed with multiple myeloma and should be considered as one of the possible differential diagnoses for cats presented with pleural effusion and hyperglobulinaemia. The diagnostic, therapeutic and prognostic aspects of this manifestation are discussed.

A series of heterogeneous lymphoproliferative diseases with CD3 and MUM1 co-expressed in cats and dogs

Lymphoma diagnosis in dogs and cats is continually evolving as new subtypes and human correlates are being recognized. In humans, T-cell lymphomas with MUM1 expressed and plasma cell neoplasia or B-cell lymphomas with CD3 expressed aberrantly are reported only rarely. We report here a case series of tumors in dogs and cats with CD3 and MUM1 co-expressed as determined by immunocytochemistry or immunohistochemistry. Lineage was assigned for these tumors by 3 board-certified pathologists and a veterinary immunologist based on review of clinical and cellular features and the results of ancillary testing including PCR for antigen receptor rearrangements, flow cytometry, and serum protein electrophoresis with immunofixation. In cats, 7 of 7 tumors, and in dogs, 3 of 6 tumors with CD3 and MUM1 co-expressed had clonal rearrangement of the immunoglobulin gene or serum monoclonal immunoglobulin, consistent with a diagnosis of a plasma cell neoplasia or myeloma-related disorder with CD3 expressed aberrantly. Disease was often disseminated; notably, 3 of 7 feline cases had cutaneous and/or subcutaneous involvement in the tarsal area. In dogs, 3 of 6 cases had a clonal T-cell receptor gamma result and no clonal immunoglobulin gene rearrangement and were diagnosed as a T-cell tumor with MUM1 expressed. The use of multiple testing modalities in our series of tumors with plasma-cell and T-cell antigens in dogs and cats aided in the comprehensive identification of the lymphoproliferative disease subtype.

Multiple myeloma, a quintessential malignant disease of aging: a geroscience perspective on pathogenesis and treatment

Multiple myeloma (MM) is an incurable plasma cell malignancy, which is predominantly a disease of older adults (the median age at diagnosis is 70 years). The slow progression from asymptomatic stages and the late-onset of MM suggest fundamental differences compared to many other hematopoietic system-related malignancies. The concept discussed in this review is that age-related changes at the level of terminally differentiated plasma cells act as the main risk factors for the development of MM. Epigenetic and genetic changes that characterize both MM development and normal aging are highlighted. The relationships between cellular aging processes, genetic mosaicism in plasma cells, and risk for MM and the stochastic processes contributing to clonal selection and expansion of mutated plasma cells are investigated. In line with the DNA damage accumulation theory of aging, in this review, the evolution of monoclonal gammopathy to symptomatic MM is considered. Therapeutic consequences of age-dependent comorbidities that lead to frailty and have fundamental influence on treatment outcome are described. The importance of considering geriatric states when planning the life-long treatment course of an elderly MM patient in order to achieve maximal therapeutic benefit is emphasized.

A challenging case of lymphoproliferative disease in a cat

A 7-year-old male castrated Maine Coon cat presented with edema of the right hindlimb and a markedly enlarged right popliteal lymph node. A CBC showed a neutropenia of 1.5 × 10³ /μL. Radiographs and ultrasonographic examination were unremarkable. Cytology of the right popliteal lymph node revealed a mixed population of cells, consisting predominantly of medium to large plasmacytoid lymphocytes, low to moderate numbers of well-differentiated plasma cells and low numbers of small lymphocytes. Plasmacytoid lymphocytes had round nuclei with finely stippled chromatin and one prominent round nucleolus. Low numbers of binucleated cells and bizarre mitotic figures, and rare multinucleated cells were observed. Histopathologic examination of the lymph node showed effacement of the normal lymph node architecture by dense sheets of neoplastic cells. Round to polygonal tumor cells of intermediate size had a low to moderate amount of cytoplasm. Round to indented hyperchromatic nuclei were often eccentrically located and contained one distinct nucleolus. Anisocytosis and anisokaryosis were moderate and 21 mitoses/10 high power field (HPF) were present. Congo red staining was negative. High numbers of tumor cells were positive for lambda light chain immunoglobulin; moderate numbers stained positive for MUM-1. A clonal BCR gene rearrangement was detected with an immunoglobulin heavy chain target (IGH), immunoglobulin lambda light chain (IgL), and kappa deleting element (Kde). Differential diagnoses for the lymphoproliferative disease in this cat included lymphoplasmacytic lymphoma and myeloma-related disorder.

Periarticular plasma cell tumors in cats

This report describes periarticular plasma cell tumors with abundant amyloid in 11 cats. The tarsus was the most commonly affected joint (10/11), and the masses were often circumferential around the tarsal joint, involving the dermis and subcutis. The 2 cases in which synovium was examined had neoplastic cells expanding the synovium. Three of the 5 cases staged radiographically had bony lysis of the affected joint. Cutaneous biopsy specimens often consisted of more amyloid than plasma cells, making the diagnosis difficult on small samples. Follow-up information was available in 7 cases; in those cases, the median survival was 194 days (range 53-671 days). Four cases had confirmed metastases, most often to regional lymph nodes, liver, and spleen. Although canine cutaneous plasma cell tumors are typically benign, those with abundant amyloid surrounding the joints of cats may involve deeper tissues and have a more aggressive behavior. These tumors can be difficult to diagnose due to low cellularity and abundant amyloid.

Histological and immunohistochemical features suggesting aetiological differences in lymph node and (muco)cutaneous feline tuberculosis lesions

OBJECTIVES

To identify and describe histological and immunohistochemical criteria that may differentiate between skin and lymph node lesions associated with Mycobacterium (M.) bovis and M. microti in a diagnostic pathology setting.

MATERIALS AND METHODS

Archived skin and lymph node biopsies of tuberculous lesions were stained with haematoxylin and eosin, Ziehl-Neelsen and Masson's Trichrome. Immunohistochemistry was performed to detect the expression of calprotectin, CD3 and Pax5. Samples were scored for histological parameters (i.e. granulomas with central necrosis versus small granulomas without central necrosis, percentage necrosis and/or multinucleated giant cells), number of acid-fast bacilli (bacterial index) and lesion percentage of fibrosis and positive immunohistochemical staining.

RESULTS

Twenty-two samples were examined (M. bovis n=11, M. microti n=11). When controlling for age, gender and tissue, feline M. bovis-associated lesions more often featured large multi-layered granulomas with central necrosis. Conversely, this presentation was infrequent in feline M. microti-associated lesions, where small granulomas without central necrosis predominated. The presence of an outer fibrous capsule was variable in both groups, as was the bacterial index. There were no differences in intralesional expression of immunohistochemical markers.

CLINICAL SIGNIFICANCE

Differences in the histological appearance of skin and lymph node lesions may help to infer feline infection with either M. bovis or M. microti at an earlier stage when investigating these cases, informing clinicians of the potential zoonotic risk. Importantly, cases of tuberculosis can present with numerous acid-fast bacilli. This implies that a high bacterial index does not infer infection with non-zoonotic non-tuberculous mycobacteria.

Paraneoplastic ganglioradiculoneuritis in a cat with a plasma cell tumour

Case summary

An 8-year-old neutered female domestic longhair cat was presented for investigation of a 48 h history of lethargy and pelvic limb ataxia. MRI of the spinal cord and vertebral column (C1 to sacrum) and brain was unremarkable. Lumbar cerebrospinal fluid analysis revealed pleocytosis and increased protein concentration. Thoracic radiographs and abdominal ultrasound were unremarkable. Anti-inflammatory doses of prednisolone were administered. Clinical deterioration occurred over the following 2 days, with the development of lower motor neuron deficits in both thoracic limbs. On repetition of the MRI, bilateral enlargement, T2-weighted hyperintensity, and marked contrast enhancement of the C7, C8 and T1 nerve roots, spinal nerves and brachial plexuses were observed. Infectious disease testing was negative. An immune-mediated inflammatory process was suspected and immunosuppressive doses of prednisolone were commenced. The clinical signs improved transiently, but marked deterioration occurred after 2 weeks. The patient was euthanased and a post-mortem examination was performed. A lymphocytic inflammatory infiltrate was detected in the C7, C8 and T1 nerve roots and dorsal root ganglia, and neoplastic plasma cells were identified in multiple organs. A diagnosis of non-cutaneous extramedullary plasmacytoma with multiorgan involvement and paraneoplastic ganglioradiculoneuritis was reached.

Relevance and novel information

Paraneoplastic ganglioradiculoneuritis in association with a plasma cell neoplasia has not been previously reported in the cat and should be considered as a differential diagnosis for cats with clinical or imaging evidence of an inflammatory process affecting the nerve roots, spinal nerves or brachial plexuses.

Primary duodenal plasmacytoma with associated primary (amyloid light-chain) amyloidosis in a cat

Case summary

A 14-year-old spayed female American Shorthair cat was presented with weight loss and a palpable abdominal mass. Abdominal ultrasound and CT revealed a duodenal mass with suspected perforation and an enlarged jejunal lymph node. Cytological evaluation from a fine-needle aspiration of the abdominal mass displayed many atypical round cells, some with a small amount of light pink material at the cellular edge. The duodenal mass was surgically removed, and was diagnosed as a plasma cell tumour immunohistochemically positive for CD79 alpha, IgA and lambda immunoglobulin light chains. In addition, amyloidosis was detected. PCR to assess the antigen receptor rearrangement of the tumour cells showed a monoclonal rearrangement of the immunoglobulin heavy chain gene. Postoperatively, the cat received chemotherapy with cyclophosphamide and prednisolone. Owing to progressive enlargement of the jejunal lymph node, different chemotherapy protocols were used sequentially, namely chlorambucil, lomustine and L-asparaginase. However, the cat died 96 days after the initial diagnosis. Post-mortem examination confirmed systemic dissemination of tumour cells. The cause of death was considered to be a result of a complication of the tumour itself and associated amyloidosis.

Relevance and novel information

This patient was diagnosed with a primary duodenal plasmacytoma, and primary (amyloid light-chain) amyloidosis. In cats, intestinal plasmacytoma is rarely reported and associated amyloidosis is an uncommon feature, when compared with humans. To our knowledge, this is the first clinical report of duodenal plasmacytoma in a cat. The present report shows that feline plasmacytomas should be included in the differential diagnosis of a duodenal mass.

Giant Cell Sarcomas in Domestic Rabbits (Oryctolagus cuniculus)

Multinucleated giant cells (MGCs) are a prominent histological feature of various mesenchymal neoplasms and are often considered a criterion of malignancy. Mesenchymal neoplasms with MGCs for which the cell lineage is unclear generally are referred to as giant cell sarcomas. Here we characterize the gross, histologic, and immunohistochemical features of 90 giant cell sarcomas in domestic pet rabbits. Based on the anatomic location and histologic and immunohistochemical findings, 18 cases were classified as histiocytic sarcomas (HS) and 72 cases as anaplastic sarcomas (AS). At postmortem examination, HS was either localized HS (n = 7) always affecting the lungs, or disseminated HS (n = 10) that affected the lungs (n = 10), liver (n = 6), kidneys (n = 4), pleura (n = 2), mediastinum (n = 2), heart (n = 4), skeletal muscle (n = 1), adipose tissue (n = 1), and lymph node (n = 1). Additionally, one cecal biopsy was consistent with HS. Microscopically, HS were characterized by sheets of neoplastic polygonal to round cells that contained single to several, often greatly enlarged nuclei as well as abundant cytoplasm. HS were always positive for CD204 and always negative for SMA and desmin. In contrast, AS arose most commonly from the skin or subcutis (n = 62) and rarely the skeletal muscle (n = 8) or abdominal organs (n = 2). In 29% of extra-abdominal AS, the tumor deeply invaded into surrounding connective tissue, skeletal muscle, tendons, and bone causing pathological fractures. Five of 9 postmortem cases metastasized to various organs often including the lungs. Microscopically, AS were characterized by sheets of spindle or pleomorphic cells admixed with variable numbers of MGCs. Immunohistochemically, AS were always negative for CD204 and often (71%) positive for SMA and/or desmin.

Protein characterization using electrophoresis and immunofixation; a case-based review of dogs and cats

Protein electrophoresis and immunotyping can be a useful adjunct to the standard biochemical techniques for characterizing serum and urine proteins. This paper reviews currently available and commonly used methods for diagnostic protein electrophoresis, including both agarose gel and capillary zone electrophoretic techniques and total protein assessments. Immunofixation and immunosubtraction methods for identification of immunoglobulin location and class are also presented. Practical application of quality assurance and quality control strategies in compliance with American Society of Veterinary Clinical Pathology (ASVCP) best practices are discussed. Commonly encountered serum and urine electrophoretic diagnostic patterns, including electrophoretically normal, acute-phase protein responses, polyclonal gammopathies, restricted polyclonal/oligoclonal gammopathies, paraproteinemias (monoclonal or biclonal gammopathies), and Bence-Jones proteinurias are also reviewed using relevant case material. Cases in which immunofixation electrophoresis are particularly useful are highlighted, and methodologies to more accurately quantify serum monoclonal proteins (M-proteins), monitoring tests commonly used in human medicine, are discussed.

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

Background

Multiple myeloma (MM) in dogs typically is treated with melphalan. A daily melphalan dosing schedule reportedly is well tolerated and associated with favorable outcome. Although anecdotally a pulse dose regimen has resulted in successful responses, little long‐term outcome and safety data is available regarding this dosing regimen for dogs with MM.

Hypothesis/objectives

(1) To compare outcome and adverse event profiles between pulse dose and daily dose melphalan schedules and (2) to report prognostic factors in dogs with MM treated with melphalan. We hypothesized that both protocols would have similar outcomes and tolerability.

Animals

Thirty‐eight client‐owned dogs diagnosed with MM receiving pulse dose (n = 17) or daily dose (n = 21) melphalan.

Methods

Retrospective cohort study assessing outcome and adverse events in dogs receiving either protocol. Risk factors were evaluated for their prognostic relevance.

Results

Both regimens were well tolerated and similarly effective, with an overall median survival time of 930 days. Renal disease and neutrophil‐to‐lymphocyte ratio (NLR) were negative prognostic factors, whereas hypercalcemia and osteolytic lesions were not prognostic factors in this study population.

Conclusions and Clinical Importance

Positive results support the use of either dosing regimen for the treatment of dogs with MM, and renal disease and NLR were negative prognostic factors. Prospective, controlled, and randomized studies are warranted to confirm these findings.

Multiple myeloma in an Amur tiger (Panthera tigris altaica)

The Amur tiger (Panthera tigris altaica) is an endangered tiger subspecies. An adult zoo-bred female was found collapsed, and died despite supportive treatment. Hematology and biochemistry showed pancytopenia and hyperglobulinemia, and serum protein electrophoresis revealed a monoclonal band in the β-globulin region. Necropsy demonstrated hemoabdomen, multifocal lytic bone marrow lesions, splenomegaly, and hemorrhagic hepatic nodules, with left medial lobe rupture. There were mutifocal hemorrhages in the subcutis, lung, epicardium, and intestinal mucosa. Histopathology demonstrated plasmacytoid cells infiltrating the bone marrow, liver and spleen, and circulating within blood vessels. On immunohistochemistry, cell infiltrates of the three tissues were positive for λ light chains, bone marrow infiltrates were positive for MUM-1 and bone marrow and spleen infiltrates were positive for CD20. These findings indicate that this animal died of hemoabdomen subsequent to multiple myeloma. This is the first time this disease has been reported in a tiger.

The feline blood film

Practical relevance: Many veterinary practices have invested in quality automated hematology instruments for use in-house. However, regardless of their specific choice of analyzer, there are important hematology findings that can only be determined by microscopic examination of stained blood films. For this reason, and also for the purpose of quality control for the analyzer, a quick blood film review should be performed alongside every automated complete blood count. Even those practices that submit their blood samples to outside diagnostic laboratories for evaluation, still require the capability to examine stained blood films in emergency situations. Series outline: This is the second of a two-part article series that aims to familiarize the practitioner with normal findings on feline blood films, with a particular focus on unique features in the cat, as well as to assist with interpretation of common abnormalities. Part 2 focuses on the morphology of feline leukocytes and platelets in health and disease. Evidence base: The information and guidance offered is based on the published literature and the author's own extensive clinical pathology research.

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

ABSTRACT Extramedullary noncutaneous plasmacytoma (ENP) is a myeloproliferative disorder of plasma cells that rarely affects cats. This paper describes an ENP case revealed by fine needle aspiration cytology (FNAC) of the mass in the skeletal muscle of an 8-month-old, male, mixed breed cat, which had a nodule in the left hind limb. The rapid immunoassay test confirmed the presence of feline leukemia virus (FeLV). The animal necropsy macroscopically showed the nodule came from the semimembranosus muscle. Histopathological examination ratified the cytological findings. Thus, this paper alerts to the existence of plasmacytoma located in the skeletal muscle of feline species. FNAC is a quick and efficient method for diagnosis of ENP.

Application of native agarose gel electrophoresis of serum proteins in veterinary diagnostics

Electrophoretic techniques, used to separate mixtures of electrically charged particles, are widely used in science. One of these techniques, native protein electrophoresis in an agarose gel, is applied in human and veterinary medicine. Changes in the proportions of individual protein fractions correspond to significant changes in the physiology of the body. Although the pattern obtained by electrophoretic separation rarely indicates a specific disease, it provides valuable information for the differential diagnosis. Decades of research on the types of patterns obtained in the case of particular diseases have led to the accumulation of substantial knowledge. The paper presents the available information on this topic. Serum protein electrophoresis is recommended in cases of increased levels of total protein in order to reveal the nature of the process. The basic information which can be obtained from electrophoretic separation includes the immune status of the organism. Both increased antigenic stimulation and immunodeficiency are clearly visible in electropherograms. Moreover, the level of heterogeneity of the corresponding protein fractions can help to distinguish between infectious diseases and cancer - multiple myeloma - the latter producing a homogeneous immunoglobulin fraction. Analysis of other protein fractions helps to detect or confirm an ongoing inflammatory process and provides information regarding liver function. Even when the concentration of total protein is within the reference range, this analysis can be recommended as a basic laboratory test.

Bimodal immunoglobulin A gammopathy in a cat with feline myeloma-related disorders

A 10-year-old female spayed mixed breed cat with a subcutaneous mass on the right hind limb was revealed with bimodal monoclonal gammopathy composed of IgA by immunoelectrophoresis and immunofixation. Approximately 1 month after referral, the cat died due to renal failure. Postmortem immunohistopathologic evaluation of the subcutaneous mass revealed neoplastic cell proliferation of plasma cells and giant myeloma cells. Neoplastic cells were also present in the liver and spleen. These results led to the diagnosis of a rare case of feline myeloma-related disorders with extramedullary plasmacytoma infiltrating in multiple locations. This report emphasizes the necessity to accumulate cases with similar clinicopathologic findings in the future.

Clinical Signs, Treatment, and Outcome in Cats with Myeloma-Related Disorder Receiving Systemic Therapy

Myeloma-related disorder (MRD) is an uncommon disease in cats, for which there is no established standard of care. In this retrospective study, we evaluated presentation, response to treatment, and toxicity in cats with MRD receiving systemic treatment. Previously reported prognostic factors were evaluated for their impact on survival in cats receiving chemotherapy. Of fifteen cases identified, thirteen received melphalan or cyclophosphamide +/- corticosteroids as first-line therapy. Chlorambucil was commonly used as rescue therapy in cats with progressive disease, or in cases of chemotherapy-related toxicity with first line agents. Overall response rates were 71% and 83% for melphalan- and cyclophosphamide-treated cats, respectively. Discontinuation of melphalan due to toxicity was common. Survival times for cats initially treated with melphalan or cyclophosphamide were not significantly different (median 252 and 394 days, respectively), and no statistically significant prognostic factors were identified. This study suggests that the combination of cyclophosphamide and corticosteroids is well tolerated and may be considered as first-line therapy for cats with systemic MRD.

Co-infection with Anaplasma platys, Bartonella henselae, Bartonella koehlerae and 'Candidatus Mycoplasma haemominutum' in a cat diagnosed with splenic plasmacytosis and multiple myeloma

Anaplasma platys (Apl), 'Candidatus Mycoplasma haemominutum' (CMh), Bartonella henselae (Bh) and Bartonella koehlerae (Bk) were confirmed by polymerase chain reaction (PCR) amplification and DNA sequencing in a cat diagnosed with multiple myeloma. Other inconsistently documented hematologic abnormalities included anemia, thrombocytopenia, eosinophilia and hypoglycemia. Persistent Apl infection was confirmed for the first time in a North American cat by sequencing three bacterial genes (16S rRNA, p44 and GroEL) in peripheral blood samples collected 100 days apart. Following doxycycline treatment for Apl, multiple myeloma was diagnosed based upon a monoclonal gammopathy and splenic plasmacytosis, and the cat was treated with melphalan, chlorambucil and prednisolone. Apl DNA was not amplified from post-treatment blood samples and the hyperglobulinemia resolved temporarily following chemotherapy. Retrospective PCR analysis of stored DNA extracts identified CMh, Bk and Bh infections. Retrospective PCR for antigen receptor rearrangements (PARR) of splenic aspirates did not confirm B- or T-cell clonality. Co-infection with multiple vector-borne pathogens should be a diagnostic consideration in cats with chronic hypergammaglobulinemia, monoclonal gammopathy and splenic plasmacytosis.

Multiple myeloma in a captive lion (Panthera leo)

Multiple myeloma is a rare, systemic proliferation of neoplastic plasma cells. A case was reported in an 11-year-old male captive lion (Panthera leo) at the National Zoological Gardens of South Africa, Pretoria. The classic features of symptomatic multiple myeloma were all evident in this case; namely osteolytic lesions, monoclonal gammopathy in the serum with excretion of monoclonal proteins in the urine, neoplastic plasma cells in the bone marrow and associated renal failure and anaemia. In addition, similar to the common pattern of this disease in domestic felids, at least three extramedullary tumours were found and several organs were infiltrated by neoplastic plasma cells. The cytoplasm of approximately 50%of the neoplastic round cells, including a few giant myeloma cells, stained weakly to strongly using immunohistochemical stains for B-lymphocytes (CD79a). The normal haematological parameters and lack of any osteolytic lesions in the lion at the time of the first evaluation suggest that the primary neoplastic cells could have originated from one of the extramedullary tumour sites. Only two cases of multiple myeloma have previously been reported in captive wild felids. To the authors’ knowledge, there are no case reports of multiple myeloma in lions.

Multiplex PCR and Genescan analysis to detect immunoglobulin heavy chain gene rearrangement in feline B-cell neoplasms

Lymphoid neoplasms are usually diagnosed on the basis of cytological and histopathological findings. However, in some cases, discrimination of lymphoid neoplasms from reactive lymphoid proliferation is difficult. PCR amplification of complementarity-determining region 3 (CDR3) of the immunoglobulin heavy-chain variable region (IGHV) gene can be used to assess clonality of B-cell populations as a supportive diagnostic tool for B-cell neoplasms. Because of the sequence variation and possible somatic hypermutation of the IGHV gene, sensitivity of the PCR-based assay to detect clonal IGHV gene rearrangement largely depends on the sequences and numbers of primer sets. Prior to the development of an efficient assay, we cloned and sequenced 97 IGHV complementary DNAs (48 IGHV-1 and 49 IGHV-3 clones) from normal cat spleens. On the basis of these sequences, we designed 6 forward primers at the variable region and 5 reverse primers at the joining region. Using each of 6 forward primers and a mixture of 5 reverse primers, we amplified CDR3 of IGHV genes and analyzed the PCR products by conventional PAGE and Genescan analyses using fluorescence-labeled primers. Twenty-six feline B-cell neoplasms diagnosed by histopathological and immunohistochemical examinations were subjected to the newly developed analysis of IGHV gene rearrangement. Clonal IGHV gene rearrangement was detected in 22 of 26 (84%) samples by both PAGE and Genescan analyses. To reduce the number of PCR reactions, we constructed a multiplex PCR analysis system using a mixture of IGHV-1- and IGHV-3-specific primers as forward primers and a mixture of 5 joining region reverse primers. Results of the multiplex PCR were 100% concordant with those obtained by each of the singleplex PCRs. The multiplex PCR-based assay and Genescan analysis developed in the present study would be useful and practical tools to detect clonal IGHV gene rearrangement in feline B-cell neoplasms.

Myeloma-related disorder with leukaemic progression in a cat

A 10-year-old American Shorthair cat with nasal discharge, anorexia, and weight loss was found to have pancytopenia and hyperproteinaemia. Bone marrow aspiration revealed atypical plasma cells that totalled 50% of the nucleated bone marrow cells. The number of atypical plasma cells progressively increased in the peripheral blood during the observation period of 64 days. The cat did not respond to treatments with melphalan, chlorambucil, and prednisolone, and died 71 days after the initial presentation. Clinical, cytological, histopathological, and immunohistochemical findings in this case supported the diagnosis of myeloma-related disorder (MRD) with leukaemic progression.