Differentiating Benign and Malignant Causes of Lymphocytosis in Feline Bone Marrow

Reference intervals for bone marrow cells in juvenile and young adult cats bone marrow cytology

BACKGROUND

The current bone marrow (BM) reference intervals (RI) are based on a limited number of cats. Age-related changes in BM variables might be important,possibly affecting the interpretation of the results.

OBJECTIVES

Establish BM cytologic reference intervals (RIs) and association of age and sex on these findings, in healthy juvenile and young adult cats.

METHODS

BM aspirates of cats deemed healthy based on history and clinical, CBC, serum chemistry findings, and negative retrovirus serology were obtained and examined cytologically. The examination included a 1000-nucleated differential cell count and cell morphologic assessment. RIs were calculated using parametric, robust, and nonparametric methods. The cytologic findings were examined for associations with sex and age.

RESULTS

The study included 40 cats (females, 22 [55%]; males, 18 [45%]) with a median age of 1.5 years (range 0.5-5). Most calculated RIs were similar to those previously reported. BM plasma cell and monocyte counts were weakly and positively correlated with age (rs, .312 and .373, respectively; P < .05). Metarubricytes were higher infemales (mean, 25.1%; SD, 6.0%) than males (mean, 21.2%; SD, 6.0%; P < .05).

CONCLUSIONS

The BM differential cell counts determined in this study can serve as RIs for cats aged 0.5-5 years.

2022 Update of the Consensus on the Rational Use of Antithrombotics and Thrombolytics in Veterinary Critical Care (CURATIVE) Domain 1- Defining populations at risk

OBJECTIVES

To expand the number of conditions and interventions explored for their associations with thrombosis in the veterinary literature and to provide the basis for prescribing recommendations.

DESIGN

A population exposure comparison outcome format was used to represent patient, exposure, comparison, and outcome. Population Exposure Comparison Outcome questions were distributed to worksheet authors who performed comprehensive searches, summarized the evidence, and created guideline recommendations that were reviewed by domain chairs. The revised guidelines then underwent the Delphi survey process to reach consensus on the final guidelines. Diseases evaluated in this iteration included heartworm disease (dogs and cats), immune-mediated hemolytic anemia (cats), protein-losing nephropathy (cats), protein-losing enteropathy (dogs and cats), sepsis (cats), hyperadrenocorticism (cats), liver disease (dogs), congenital portosystemic shunts (dogs and cats) and the following interventions: IV catheters (dogs and cats), arterial catheters (dogs and cats), vascular access ports (dogs and cats), extracorporeal circuits (dogs and cats) and transvenous pacemakers (dogs and cats).

RESULTS

Of the diseases evaluated in this iteration, a high risk for thrombosis was defined as heartworm disease or protein-losing enteropathy. Low risk for thrombosis was defined as dogs with liver disease, cats with immune-mediated hemolytic anemia, protein-losing nephropathy, sepsis, or hyperadrenocorticism.

CONCLUSIONS

Associations with thrombosis are outlined for various conditions and interventions and provide the basis for management recommendations. Numerous knowledge gaps were identified that represent opportunities for future studies.

Presumptive precursor-targeted immune-mediated anemia concurrent with gastrointestinal lymphoma in a cat

A 10-year-old spayed female mixed-breed cat presented with progressive nonregenerative anemia. Clinicopathological abnormalities included severe nonregenerative anemia (packed cell volume [PCV]: 7%, aggregate reticulocytes: 1.12 × 10³/µl) and a hypoechogenic mass well-localized in the stomach. Bone marrow (BM) smears revealed increased particle hematopoietic cellularity with decreased myeloid:erythroid (M:E) ratios, no dysplasia of any lineage, and presence of erythroid precursors phagocytized by macrophages. The cat was diagnosed with presumptive precursor-targeted immune-mediated anemia (PIMA). The stomach mass was consistent with CD 20 positive T-cell lymphoma. The lymphoma was completely resected via surgery, and the PIMA was cured by immunosuppressive therapy. On day 410, both diseases have not recurred without medications. This is the first report of feline PIMA and concurrent gastrointestinal lymphoma.

Immunophenotypic characterization and clinical outcome in cats with lymphocytosis

Background

Lymphocytosis is relatively common in cats, but few studies describe lymphocyte populations or the clinical course associated with different immunophenotypic expansions.

Hypothesis/Objectives

We hypothesized that cats frequently develop non‐neoplastic lymphocytosis and that different neoplastic immunophenotypes have variable prognoses. We aimed to characterize the lymphocyte expansions in a large population of cats with lymphocytosis and to assess clinical presentation and outcome in a subset.

Animals

Three cohorts of cats older than 1 year with lymphocytosis (>6000/μL) were examined to define immunophenotypic categories (n = 146), evaluate outcome (n = 94), and determine prevalence of immunophenotypes (n = 350).

Methods

Retrospective study of cats with blood submitted for flow cytometry. Medical records (n = 94) were reviewed for clinical data, treatment, and survival information.

Results

Five major immunophenotypic categories were identified: B cell, heterogeneous (≥2 lineages expanded), CD4+ T cell, CD4−CD8− (double negative [DN]) T cell, and CD5‐low‐expressing T cell. B‐cell and heterogeneous phenotypes were more consistent with a non‐neoplastic process, having polyclonal antigen receptor gene rearrangements, younger age at presentation, lower lymphocyte counts, and prolonged survival. The neoplastic phenotypes, CD4+ T cell, DN T cell, and CD5 low T cell, had different median survival times (752 days [n = 37], 271 days [n = 7], 27.5 days [n = 12], respectively). Among CD4+ T‐cell cases, cats with abdominal lymphadenopathy, intestinal involvement, or both and females had shorter survival. Among 350 cats with lymphocytosis, CD4+ T‐cell lymphocytosis was most common, followed by heterogeneous and B‐cell phenotypes.

Conclusions and Clinical Importance

Neoplastic CD4+ T‐cell lymphocytosis is common in cats and has a prolonged clinical course compared to aberrant T‐cell phenotypes. Cats with heterogeneous and B‐cell lymphocyte expansions commonly have non‐neoplastic disease.

Assessment of immunoglobulin heavy chain, immunoglobulin light chain, and T-cell receptor clonality testing in the diagnosis of feline lymphoid neoplasia

BACKGROUND

Differentiation between neoplastic and reactive lymphocytic proliferations can be challenging in cats. PCR for antigen receptor rearrangements (PARR) testing is a useful diagnostic tool to assess clonality of a lymphoid population. Previous feline PARR studies evaluated clonality of complete immunoglobulin heavy chain V-D-J (IGH-VDJ) and T-cell receptor gamma (TRG) gene rearrangements.

OBJECTIVES

We aimed to evaluate the sensitivity and specificity of feline PARR primers targeting complete IGH-VDJ and TRG rearrangements, as well as incomplete IGH-DJ, kappa deleting element (Kde), and immunoglobulin lambda light chain (IGL) gene rearrangements in defined feline neoplasms and nonneoplastic controls.

METHODS

Fluorescently labeled PCR primers were designed to amplify complete IGH-VDJ, incomplete IGH-DJ, Kde, IGL, and TRG gene rearrangements in two multiplexed PCR reactions, and PCR products were analyzed by fragment analysis. Fresh tissue samples from 12 flow cytometrically confirmed B-cell lymphomas, 26 cytologically confirmed gastric and renal lymphomas of presumed B-cell origin, 30 flow cytometrically confirmed T-cell leukemias, and 11 negative control cats were tested.

RESULTS

Using four immunoglobulin primer sets (IGH-VDJ, IGH-DJ, Kde, and IGL), clonal immunoglobulin rearrangements were detected in 87% (33/38) of the presumed B-cell neoplasms. The IGH-VDJ reaction alone only detected clonality in 50% (19/38) of these cases. TRG rearrangements were clonal in 97% (29/30) of the T-cell leukemia cases. All negative control samples had polyclonal immunoglobulin and TRG rearrangements.

CONCLUSIONS

The PARR assay developed in this study is useful for assessing clonality in feline lymphoid neoplasms. Clonality assessment of incomplete IGH-DJ, Kde, and IGL rearrangements helped identify clonal B-cell neoplasms not detected with complete IGH-VDJ PARR alone.

Feline non-regenerative anemia: Diagnostic and treatment recommendations

PRACTICAL RELEVANCE

Non-regenerative anemia, or anemia with reticulocytopenia, is a daily diagnosis in feline practice.

CLINICAL CHALLENGES

The disease processes underlying non-regenerative anemia are many and diverse. A major diagnostic evaluation may be required to correctly diagnose and treat the underlying cause.

AUDIENCE

All veterinarians caring for cats will face the diagnostic and therapeutic challenge of non-regenerative anemia. Readers will benefit from the review of diagnostic testing and therapeutic options for non-regenerative anemia.

EVIDENCE BASE

This review summarizes the currently available literature informing diagnostic and treatment recommendations related to non-regenerative anemia. The evidence available to support the recommendations in this review is graded as low and includes predominantly expert opinion, case reports and cases series, on which the authors' interpretation/consensus is based.

Retrospective study of 152 feline cytological bone marrow examinations: preliminary classification and ranges

OBJECTIVES

Cytological assessment of the bone marrow is an essential tool for understanding and investigating haematological abnormalities. Sometimes it represents the only way to reach a definitive diagnosis. The purpose of this study was to provide a general overview regarding the prevalence of feline bone marrow disorders encountered in a private European laboratory setting, to classify them and to assess the differential cell counts related to such disorders.

METHODS

In total, 152 bone marrow samples were classified using cytological and numerical criteria. The bone marrow cytological examinations were performed after the identification of haematological alterations, such as cytopenias, increased number of cells or suspicion of malignant blood disorders.

RESULTS

Of the 152 bone marrow samples evaluated, 71 (46.7%) were classified as hyperplastic, primarily granulocytic and erythroid hyperplasia (50.7% and 45.1%, respectively, of the total hyperplasia); 23 (15.1%) showed dysmyelopoiesis, mainly in the form of myelodysplastic syndrome (39.1% of the total dysmyelopoiesis); 21 (13.8%) had no cytological abnormalities; 17 (11.2%) were malignant blood disorders; 15 (9.9%) had hypoplastic conditions; and two (1.3%) were miscellaneous diseases. Metastatic disease was detected in only two cases (1.3%). Differential cell counts and myeloid-to-erythroid (M:E) ratios were reported for normal, erythroid hypoplastic, erythroid and granulocytic hyperplastic and dysplastic conditions.

CONCLUSIONS AND RELEVANCE

This study provides a general overview of the prevalence and incidence of feline bone marrow disorders together with ranges for differential nucleated cell counts and M:E ratios for the various conditions reported.

Diagnostic bone marrow sampling in cats

Practical relevance: Hematologic disorders are relatively common in cats, as inflammatory, immune-mediated and infectious diseases have the potential to impact erythroid, myeloid and thrombopoietic lines within the bone marrow. Clinical challenges: Clinicians often benefit from information obtained from bone marrow cytology and histopathology in diagnosing hematologic disorders in feline patients. However, these sampling procedures are ones that many veterinarians are intimidated by and thus not comfortably performing in clinical practice.

AUDIENCE

This review, aimed at all veterinarians who treat cats, highlights the reasons a clinician may elect to sample bone marrow, and details the collection of bone marrow for both cytology and histopathology. Potential complications and limitations of each procedure are also reviewed. Evidence base: The collection of bone marrow for cytology and histopathology is not new to feline medicine and several research studies have investigated various sampling modalities in cats. This article offers a comprehensive review of the currently accepted best practices.

Demographic Characteristics, Survival and Prognostic Factors for Mortality in Cats with Primary Immune-Mediated Hemolytic Anemia

BACKGROUND

Immune-mediated hemolytic anemia (IMHA) is uncommon in cats, but may result in severe disease. Demographic predispositions for development of the disease and prognostic factors for mortality have not been investigated previously.

HYPOTHESIS/OBJECTIVES

To explore possible demographic predispositions for development of primary IMHA in cats and to investigate possible prognostic factors for mortality.

ANIMALS

107 client-owned cats with IMHA, of which 72 had primary IMHA and 35 had secondary IMHA, and 9,194 control cats.

METHODS

Data were collected retrospectively from records of cats with IMHA, defined by the presence of anemia and concurrent autoagglutination, ghost cells without oxidative damage on fresh blood smear, positive titer in a direct antiglobulin test, or evidence of phagocytosis of erythroid precursors in bone marrow. Odds ratios were calculated to assess the risk of development of primary IMHA in different demographic groups and Cox proportional hazards analysis was conducted to evaluate prognostic factors.

RESULTS

No sex or breed predisposition was identified for the development of primary IMHA in comparison to the control cats, but cats in the age range 2.1-5.9 years were predisposed. Higher total bilirubin concentration and age were significant negative prognostic factors and higher lymphocyte numbers and serum globulin concentration were positive prognostic factors in a multivariable model.

CONCLUSIONS AND CLINICAL IMPORTANCE

Young adult cats were more likely to develop primary IMHA than other groups, but no apparent male predisposition was identified in this study, contrary to previous reports. Several prognostic factors were identified, which may be helpful in guiding clinical practice in the future.

Diagnosis and treatment of chronic lymphocytic leukemia in a bat-eared fox (Otocyon megalotis)

CASE DESCRIPTION

Severe lymphocytosis and leukocytosis were detected during examination of a 10-year-old sexually intact male bat-eared fox (Otocyon megalotis) with regionally extensive alopecia.

CLINICAL FINDINGS

A CBC revealed severe leukocytosis (39,100 leukocytes/μL) and marked lymphocytosis (90%). A blood smear consisted predominantly of intermediate-sized lymphocytes and few large lymphocytes, with mild to moderate nuclear atypia. These findings were highly suggestive of chronic lymphocytic leukemia (CLL). Cytologic evaluation of bone marrow aspirates revealed no evidence of overt malignancy, with 10% of all cells identified as small to intermediate-sized mature lymphocytes.

TREATMENT AND OUTCOME

Treatment with chlorambucil and prednisone administered orally over a 1.8-year period decreased the leukocyte and lymphocyte counts to within reference intervals with no adverse effects. Although repeated flow cytometry revealed evidence of residual disease, the fox remained free of clinical disease, and WBC counts were within reference intervals for this species. At 22 months after initial evaluation, the fox was euthanized because of debilitating arthritis. No evidence of CLL was detected grossly or histologically during necropsy.

CLINICAL RELEVANCE

To the authors' knowledge, this was the first report of CLL in a bat-eared fox and first successful treatment in a nondomestic carnivore. Treatment in accordance with a chemotherapeutic protocol successfully resolved the leukocytosis and lymphocytosis with no serious adverse effects. Description of this fox and the treatment protocol should provide a valuable reference for future cases in this and other nondomestic canine species.

Chronic lymphocytic leukaemia in the cat: 18 cases (2000-2010)

There is little information regarding the presentation, biologic behaviour, treatment and prognosis in cats with chronic lymphocytic leukaemia (CLL), and further investigation is needed to characterize this disease in cats. The goal of this study was to describe the clinical presentation, response to treatment and prognosis of feline CLL. A multi-institutional retrospective study of 18 cats diagnosed with CLL between 2000 and 2010 was performed. CLL was defined as the presence of a mature lymphocytosis (>9000 lymphocytes µL(-1) ) and confirmation of an immunophenotypically monomorphic or clonal lymphoid population. Each patient was required to also have at least one of the two following criteria: (1) concurrent cytopenia of at least one cell line and/or (2) >15% mature lymphocytes in the bone marrow. Data on signalment, history, clinical signs, clinicopathologic features and response to treatment were reviewed. Median age of the cats at initial presentation was 12.5 years (range: 5-20 years). The most common presenting complaint was chronic weight loss, which was present in 8/18 (44%) cats. Sixteen of 18 (89%) cats were treated with chlorambucil and prednisolone; four of these cats also received vincristine. Two (11%) cats were treated with multi-agent injectable chemotherapy (L-CHOP, l-asparaginase, cyclophosphamide, doxorubicin, vincristine, prednisolone). Eighty-eight percent of cats evaluable for response achieved a complete (nine cats) or partial (six cats) remission. Median overall remission was 15.7 months (range: 1.3-22.8 months). The median overall survival in the 17 cats with follow-up data was 14.4 months (range: 0.9-25.3 months). Results of this study suggest that CLL affects older-aged cats and responds favourably to treatment with oral chlorambucil and prednisolone.

The feline acute phase reaction

The acute phase reaction (APR) is a response to potentially pathogenic stimuli. It begins with the release of interleukin (IL)-1, IL-6 and tumour necrosis factor (TNF)-α from inflammatory cells. These cytokines induce fever, leucocytosis and release of serum acute phase proteins (APPs). In this review, the characteristics of the feline APR are described. In cats with inflammatory conditions, fever is a common finding, with leucocytosis due to the release of cells from the marginal pool, followed by activation of myelopoiesis. Because excitement frequently causes leucocytosis in cats, a diagnosis of inflammation should therefore be supported by additional findings such as the presence of toxic neutrophils. The major APPs are serum amyloid A and α₁-acid glycoprotein (AGP), which both increase a few hours after the inflammatory stimulus and remain elevated for as long as the inflammation persists. AGP plays an important role in the diagnosis of feline infectious peritonitis (FIP) and may also be useful also in studies of FIP pathogenesis.

Determining the Significance of Persistent Lymphocytosis

The authors provide a review of current knowledge of lymphocytosis in nonneoplastic conditions. They conclude that the list of major differentials for persistent nonneoplastic lymphocyte expansion in dogs and cats is short and that most of these conditions are relatively uncommon. Persistent lymphocytosis of small, mature, or reactive lymphocytes is most commonly the result of chronic lymphocytic leukemia or lymphoma. The first step in distinguishing nonneoplastic from neoplastic lymphocytosis is immunophenotyping by flow cytometry to determine the phenotypic diversity of the circulating cells. Clonality testing using the polymerase chain reaction for antigen receptor rearrangements assay is a useful second step in cases in which the phenotype data are equivocal. Once the diagnosis of malignancy has been established, the immunophenotype also provides prognostic information in dogs.