Diagnosis of canine lymphoid neoplasia using clonal rearrangements of antigen receptor genes

Malignant transformation of T-cell large granular lymphocyte leukemia in a dog

An 8-year-old spayed female Golden Retriever was referred to us for evaluation of mild lymphocytosis. The peripheral lymphocytes were comprised of mostly large granular lymphocytes (LGLs), and flow cytometry showed that they were mostly CD3+8+ T lymphocytes. Clonal rearrangement of the T-cell receptor gene was identified in the peripheral blood, and the dog was therefore diagnosed with LGL chronic leukemia. The dog was subclinical without treatment until hospitalization on day 154, at which point the lymphocytes looked like lymphoblasts and the surface markers changed to CD3-8-. This was regarded as malignant transformation from LGL chronic leukemia to the acute type. Sequential chemotherapy was started, but the dog died on day 190. Necropsy revealed tumor cell infiltration into the heart, skin, and brain.

A novel canine lymphoma cell line: a translational and comparative model for lymphoma research

A novel canine lymphoma cell line, OSW, was established from the malignant pleural effusion of a dog with peripheral T-cell lymphoma. The immunoprofile as determined by flow cytometry was as follows: positive for CD45, CD49d, CD18, CD11a; weakly positive for CD11b, CD11c, CD11d; and negative for CD45RA, CD1a, CD1c, CD3, TCRalphabeta, TCRgammadelta, CD4, CD5, CD8a, CD8b, CD90(Thy1), CD21, MHCII, CD14(TUK4), CD34, and MPO. Immunocytochemistry of cytospin preparations was negative for cytoplasmic CD3, CD79a, and MPO, but was positive for CD20. The cell line had an oligoclonal T-cell receptor gamma (TCRgamma) gene rearrangement. Array comparative genomic hybridization (aCGH) and single locus probe (SLP) analysis showed that there were copy number increases of loci on dog chromosome 13 (CFA 13), and copy number decreases were evident for regions of CFA 11, 22, 26, 30 and 32, which include several of the more common chromosomal aberrations reported previously in canine lymphoma. The OSW cell line grows rapidly in vitro and is tumorigenic as a xenograft in SCID/NOD mice. OSW represents one of only a few reported canine lymphoma cell lines and is the most thoroughly characterized. This cell line and xenograft represent significant in vitro and in vivo models, respectively, for comparative and translational lymphoma research.

Fast molecular diagnostics of canine T-cell lymphoma by PCR and capillary gel electrophoresis with laser-induced fluorescence detector

Lymphoma is the most common hematopoietic tumor in dogs and manifests as a proliferation of malignant lymphoid cells primarily affecting the lymph nodes or solid visceral organs. We describe the use of capillary gel electrophoresis (CGE) with a laser-induced fluorescence (LIF) detector based on polymerase chain reaction (PCR) to rapidly detect a disorder of the canine T-cell receptor gamma (TCRgamma) gene. After the PCR amplification of the specific TCR( gene in dogs, the 90-bp DNA fragment amplified was separated in a fused-silica capillary by CGE-LIF. Under an electric field of 375 V/cm and with a sieving matrix of 1.5% poly (ethyleneoxide) (M(r) 600,000), the amplified PCR products were analyzed within 4 min by CGE separation. When the CGE-LIF method was applied to real clinical samples of the specific DNA fragment of the TCR( gene, the migration time and the corrected peak area showed relative standard deviations (n=5) of 0.29% and 0.58%, respectively. Both methods of CGE-LIF and slab gel electrophoresis showed same results for nine clinical samples. This PCR/CGE-LIF technique may prove to be a new fast and simple tool for the rapid diagnosis of the PCR-amplified DNA of canine T-cell lymphoma.

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.

Genomic organization of the T-cell receptor gamma gene and PCR detection of its clonal rearrangement in canine T-cell lymphoma/leukemia

Because the T-cell receptor gamma (TCRgamma) gene is rearranged at an early stage of T-cell development in both TCRalphabeta and TCRgammadelta lineages, it has been preferentially targeted to detect T-cell clonality in human lymphoma/leukemia. We isolated 22 independent cDNA clones encoding canine TCRgamma and the following analysis of nucleotide sequences using the dog genome database revealed that the canine TCRgamma locus contains at least four repertories of variable genes that can be organized into two distinct subgroups and six repertories of joining genes belonging to two distinct subgroups according to the nucleotide sequence similarity. The findings allowed us to design PCR primers that were directed to the conserved or specific nucleotide sequences for each subgroup of variable and joining genes. By using four different combinations of primers, a PCR-based analysis was performed on cell samples collected from T-cell lymphoma/leukemia and B-cell lymphoma cases and hyperplastic and normal lymph nodes. All cell samples from 11 T-cell malignancy cases exhibited clonal amplification by two out of four primer combinations. This finding was considered to be valuable in PCR-based analysis for detecting T-cell clonality in canine lymphoma/leukemia.

Flow cytometric expression of common antigens CD18/CD45 in blood from dogs with lymphoid malignancies: A semi-quantitative study

Flow cytometry is useful to study lymphoid malignancies since it allows both immunophenotyping of neoplastic cells and quantification of antigen expression. CD18 and CD45 are commonly exposed membrane antigens with different levels of expression on blood leukocyte and neoplastic cells. The aim of this retrospective study was to semi-quantitatively evaluate the expression of CD18 and CD45 in dogs with different lymphoid malignancies with blood involvement and to compare results with those from healthy dogs and dogs with reactive diseases. Blood samples from 13 dogs with precursor lymphoid malignancies, 20 with mature neoplasms (either chronic lymphocytic leukaemia or lymphoma), of different immunophenotypes, were compared with 24 healthy dogs and 12 dogs with different reactive diseases. The median fluorescence intensity (MFI) for CD18 and CD45 was recorded on lymphoid and granulocytic populations using dual colour flow cytometry, and the ratio between MFI for lymphoid and granulocytic populations (L/N ratio) was calculated to compare the results obtained in different sessions using an internal control (granulocyte fluorescence intensity). Significant decreases in the L/N ratio were detected in neoplastic samples for both CD18 (either precursors or mature versus controls) and CD45 (either precursors or mature versus control), while using MFI only slight differences were detectable in CD45 between precursors and controls. Neoplastic cells often exhibited lower expression of the L/N ratio for CD18, and mainly for CD45, most likely due to a less mature pattern than normal cells and/or to an aberrant quantitative expression of surface antigen. Moreover, more than 50% of neoplastic lymphoid cells exhibited L/N ratios that were not within the values observed in controls for at least one antigen. Altered L/N ratios, in particular decreases of CD45, were mainly observed in precursor neoplasms and in T-cell neoplasms. Detection of altered expression of common antigens, and in particular a L/N ratio for CD45 lower than a value of 103% may be useful as a confirmation of pseudo-clonality thus helping in differentiating reactive and neoplastic lymphocyte expansions.

Use of multigeneration-family molecular dog leukocyte antigen typing to select a hematopoietic cell transplant donor for a dog with T-cell lymphoma

CASE DESCRIPTION

A 7-year-old Golden Retriever was examined because of anorexia, lethargy, vomiting, and gradual weight loss.

CLINICAL FINDINGS

Splenomegaly, pancytopenia, high serum calcium concentration, and high alkaline phosphatase activity were detected. Magnetic resonance imaging revealed an enlarged mesenteric lymph node and increased signals from the bone marrow of the ilium and vertebral bodies. Histologic examination and immunophenotyping of biopsy specimens confirmed a stage V (b) T-cell malignant lymphoma.

TREATMENT AND OUTCOME

Clinical remission was attained by use of 2 chemotherapy cycles, followed by an allogeneic hematopoietic cell transplant performed at 18 weeks after diagnosis. A donor was identified by molecular dog leukocyte antigen typing methods. The patient was conditioned with 2 fractions of 4 Gy total body irradiation delivered 3 hours apart at 7 cGy/min, followed by an IV infusion of recombinant canine granulocyte colony-stimulating factor mobilized leukapheresis product and postgrafting immunosuppression with cyclosporine. Chimerism analyses revealed full donor engraftment that has been maintained for at least 58 weeks after transplant. Remission has been confirmed by normal results of serum thymidine kinase assays and the absence of peripheral blood clonal T-cell receptor gene rearrangements.

CLINICAL RELEVANCE

Systemic chemotherapy induces remissions; however, most dogs succumb to disease recurrence because of multidrug resistance. Outcome of allogeneic hematopoietic cell transplantation in dogs can be excellent because of improved donor-recipient selection by use of molecular dog leukocyte antigen typing, compared with early attempts, and better prevention of graft versus host disease, better supportive care, and substitution of peripheral blood mononuclear cells for bone marrow.

Development of the polymerase chain reaction assay based on the canine genome database for detection of monoclonality in B cell lymphoma

From the canine genome database and its bioinformatic analysis, we identified conserved sequences within the vast majority of 61 variable segments and 1 joining segment of the immunoglobulin heavy chain (IgH) gene, and designed optimal primers for polymerase chain reaction (PCR) amplification directed at these conserved sequences to evaluate the monoclonality of IgH in canine B cell lymphoma. Using the primers, a PCR-based assay was performed on fine-needle aspiration samples of normal, hyperplasia, and malignant lymph nodes and lymphoma cell lines. All fine-needle aspiration samples of five B cell lymphoma cases and the B cell lymphoma line GL-1 exhibited clonal amplification, whereas no amplification was observed in the samples from normal and hyperplasia lymph nodes, cases of T cell lymphoma, and the T cell lymphoma line CL-1. The primers we designed clearly distinguished malignant B lymphocytes from normal, reactive, and malignant T lymphocytes, indicating a potential utility of the primers for PCR-based routine clinical examination for canine B cell lymphoma.

A non-radiometric method for measuring serum thymidine kinase activity in malignant lymphoma in dogs

The aim of this study was to evaluate an enzyme-linked immunosorbent assay (ELISA), for determination of serum thymidine kinase 1 (sTK1) activity in dogs with malignant lymphoma (ML) and compare it with a thymidine kinase (TK) radioenzymatic assay (TK-REA). The TK-REA has recently been shown to be useful in determining the clinical stage and prognosis in canine ML. In addition, serum lactate dehydrogenase (LDH) was measured. Forty-five dogs were included in the study. Sixty serum samples from these dogs, stored in a tumour serum sample bank (stored at -20 degrees C), were analysed. Apart from 37 dogs with ML, four normal dogs as well as two dogs with mammary carcinomas, one dog with bladder carcinoma, and one dog with malignant fibrous histiocytoma were included. Staging of ML was based on the modified World Health Organization (WHO) staging system for canine ML. The diagnosis of all tumours was verified by histopathology. The TK activity (units per litre [U/L]) ranged from 1.0 to 607.9 in the TK-REA analysis and from 1.1 to 510 in the TK-ELISA (normal reference value <7U/L). The range for LDH was between 12 and 1194 U/L (normal reference value <228 U/L). There was a significant correlation between the TK-REA and the TK-ELISA. The correlation coefficient (CC) was 0.97 and the standard error of the estimate (SEE) was 3.7 U/L. There was no correlation between LDH and either the TK-REA or the TK-ELISA (CC=0.53 for both assays; SEE=26.7 and 12.7 U/L, respectively). Most of the variation in LDH was still within the normal reference range. The mean LDH in dogs with high-stage (stage IV+V) disease was 201.9 U/L. The corresponding values for the TK-REA and TK-ELISA were 109 and 109.9 U/L, respectively. The significant relation between the TK-REA and the TK-ELISA was confirmed by Bland-Altman analysis. The TK-ELISA assay, because of its relative simplicity, will permit measurement of TK in cases of ML in dogs to become a routine procedure.

The role of flow cytometry in companion animal diagnostic medicine

Flow cytometry is a powerful tool for characterising the composition of complex cell populations. The accuracy and precision of this technology for describing and enumerating cells exceeds traditional methods. The number of diagnostic veterinary laboratories with access to a dedicated machine is increasing, and there is the potential to offer a clinical flow cytometry service. The improved availability of monoclonal antibodies (mAb) to cell markers expressed by the leukocytes of companion animals, permits the implementation of comprehensive mAb panels suitable for diagnosis of lympho- and myeloproliferative disease. Reticulated erythrocyte and platelet quantification, antiglobulin assays for immune-mediated cytopenias, lymphocyte subset analysis, and immunophenotyping of lymphoma and leukemia, have been validated for companion animal samples on the flow cytometer. It is now timely to consider the role of flow cytometry in diagnostic practice, and the requirement for quality assurance and standardization of testing procedures.

Prognostic Factors Associated with Survival in Dogs with Lymphocytic-Plasmacytic Enteritis

Prognostic factors associated with survival in dogs with lymphocytic-plasmacytic enteritis (LPE) were investigated through a retrospective study. Using case records, 48 dogs diagnosed with LPE were classified as survivors (n = 32) or non-survivors (n = 16), and the clinical and clinicopathological parameters were reviewed between the 2 groups by using univariate and multivariate prognostic analysis. Compared to the hospital population, non-survivors had an overrepresentation of the Shiba breed. Results of univariate analysis indicated that anorexia, severe weight loss, packed cell volume, and total protein were significantly associated with survival for 6 months after diagnosis. In multivariate analysis, anorexia and hypoproteinemia were significantly associated with survival. Furthermore, initial response to treatment was strongly associated with poor prognosis. Based on these clinical and laboratory parameters such as anorexia, hypoproteinemia and initial response to treatment, it may be possible to predict poor prognosis in canine LPE.

Immunohistochemical Diagnosis of Alimentary Lymphomas and Severe Intestinal Inflammation in Cats

Intestinal tissue samples were examined from 32 cats in which a histopathological diagnosis of alimentary lymphoma or multicentric lymphoma affecting the gastrointestinal tract had been made. These samples were re-evaluated histopathologically and serial sections were examined immunohistochemically with antisera specific for the lymphoid markers CD3, CD79a and BLA-36 and for class II molecules of the major histocompatability complex. The cats ranged in age from 4-16 years (median 10.5 years). The main presenting clinical signs were vomiting, diarrhoea and weight loss. The majority of alimentary lymphomas were of the B-cell type (n=15), whereas cases of T-cell lymphoma were fewer in number (n=8). Four cats had lymphoma of a mixed T-and B-cell phenotype. In five of the cats, immunohistochemistry suggested an inflammatory process, in contradiction to the original histopathological diagnosis of lymphoma. Immunolabelling would appear to be a useful adjunct to histopathology in classifying cases of feline alimentary lymphoma, and may help in distinguishing lymphoma from severe intestinal inflammation.

Lineage differentiation of canine lymphoma/leukemias and aberrant expression of CD molecules

Multiparameter flow cytometry analysis and specific cluster differentiation (CD) molecules were used to determine the expression profiles of B- and T-cell antigens on lymph node preparations from 59 dogs with generalized or multisystemic lymphoma. Lymph node samples from 11 healthy dogs were labeled to validate the specificity of antibodies and to formulate guidelines for interpretation of the results obtained from lymphoma samples. In normal lymph nodes, T-lymphocytes expressing CD3, CD4, or CD8 beta represented 59+/-11%, 43+/-8%, or 16+/-5% of the total cells, whereas B-lymphocytes expressing either CD21 or surface IgM (IgM) represented 37+/-9% or 14+/-5%, respectively. Small lymphocytes could be distinguished from large lymphocytes by forward light scatter. Of the patient samples 29 different breeds were represented with Golden and Labrador retriever being the most common. The lymphoma samples segregated into three groups based on CD antigen expression. Thirty cases predominantly expressed one or more combinations of CD79a, IgM, and CD21 representing a B-cell lineage. Three B-cell cases also expressed the stem cell antigen, CD34. Sixteen cases expressed one or more combinations of CD3, CD4, and CD8 consistent with a T-cell lineage and CD3+CD4+CD8--phenotype was the most common. Thirteen cases showed a mixed expression profile for T- and B-cell antigens and in three cases CD14 was highly expressed. Clinical response was poorest for T-cell lymphomas. Leukemic states occurred in all three phenotypes; but mixed cell cases had the greatest proportion. Dual immunofluorescence staining confirmed co-expression of T-cell (CD3) and B-cell antigens (CD79a or CD21) on neoplastic lymphocytes of six mixed cell cases. In one mixed cell case, dual immunostaining identified lymphocyte populations that stained mutually exclusive for CD79a and CD3. Six mixed cell lymphomas tested by PCR showed clonality for rearranged antigen receptor. Four cases that were CD79a+CD3+ had TCRgamma chain gene rearrangements, whereas two cases that were CD3+CD8+CD21+ had Ig heavy chain rearrangement. One case expressing multiple CD molecules (CD3+CD8+CD21+CD14+) was PCR negative for both Ig and TCRgamma gene rearrangement and could not be classified into a B- or T-cell lineage. We show for the first time co-expression of B- and T-cell markers on lymphoma cells that had specific T- or B-cell gene rearrangements. These findings suggest that aberrant CD molecule expression is not an uncommon finding in canine lymphomas and is a useful diagnostic marker for malignancy.

CD20 expression in normal canine B cells and in canine non-Hodgkin lymphoma

We examined the expression of CD20 in normal canine peripheral blood mononuclear cells, normal canine spleen, and canine non-Hodgkin lymphoma (NHL) to determine the feasibility of using this antigen as a diagnostic aid and as a possible target for therapy. An antibody generated against a C-terminal (intracytoplasmic) epitope of human CD20 recognized proteins of 32-36 kd in normal and malignant canine lymphocytes. This antibody showed restricted membrane binding in a subset of lymphocytes in peripheral blood, in the B-cell regions from a normal canine spleen and lymph node, and in malignant cells from 19 dogs with B-cell NHL, but not from 15 dogs with T-cell NHL. The patterns of CD20 reactivity in these samples overlapped those seen using an antibody that recognizes canine CD79a. This anti-CD20 antibody is therefore suitable as an aid to phenotype canine NHL. In contrast, normal canine B cells were not recognized by any of 28 antibodies directed against the extracellular domains of human CD20 (including the chimeric mouse-human antibody Rituximab) or by any of 12 antibodies directed against the extracellular domains of mouse CD20. Thus, the use of CD20 as a therapeutic target will require the generation of specific antibodies against the extracellular domains of canine CD20.

Distinct B-cell and T-cell lymphoproliferative disease prevalence among dog breeds indicates heritable risk

Immunophenotypes in lymphoproliferative diseases (LPD) are prognostically significant, yet causative factors for these conditions, and specifically those associated with heritable risk, remain elusive. The full spectrum of LPD seen in humans occurs in dogs, but the incidence and lifetime risk of naturally occurring LPD differs among dog breeds. Taking advantage of the limited genetic heterogeneity that exists within dog breeds, we tested the hypothesis that the prevalence of LPD immunophenotypes would differ among different breeds. The sample population included 1,263 dogs representing 87 breeds. Immunophenotype was determined by the presence of clonal rearrangements of immunoglobulin heavy chain or T-cell receptor gamma chain. The probability of observing the number of B-cell or T-cell tumors in a particular breed or breed group was compared with three reference populations. Significance was computed using chi2 test, and logistic regression was used to confirm binomial predictions. The data show that, among 87 breeds tested, 15 showed significant differences from the prevalence of LPD immunophenotypes seen across the dog population as a whole. More significantly, elevated risk for T-cell LPD seems to have arisen ancestrally and is retained in related breed groups, whereas increased risk for B-cell disease may stem from different risk factors, or combinations of risk factors, arising during the process of breed derivation and selection. The data show that domestic dogs provide a unique and valuable resource to define factors that mediate risk as well as genes involved in the initiation of B-cell and T-cell LPD.

Characterization of feline T cell receptor gamma (TCRG) variable region genes for the molecular diagnosis of feline intestinal T cell lymphoma

A diagnosis of intestinal lymphoma is currently made on the basis of clinical and morphologic criteria. This can prove problematic for many reasons that include inadequate sample size, the coexistence of lymphoma and inflammation, and the inability to assess architectural integrity of all tissue compartments in biopsy specimens obtained endoscopically. The detection of a clonal population of cells in a lymphoproliferative lesion represents an important criterion for the diagnosis of neoplasia, but this has not been assessed in feline intestinal lymphoma. T cell receptor gamma (TCRG) gene rearrangement analysis using polymerase chain reaction (PCR) is a methodology that can be used to detect clonality in T cell populations. The basis of this assay depends on the assessment of the junctional diversity that results from rearrangement of TCRG V (variable) and J (joining) gene segments. Feline TCRG transcripts from normal small intestine and spleen were obtained using a rapid amplification of cDNA ends (5'RACE) method. Limited diversity of TCRG V and J gene segments was observed. The high degree of sequence homology in the TCRG V and J gene segments was exploited to develop a PCR test for the assessment of TCRG V--J junctional diversity and hence clonality determination of T cell populations in cats. Molecular clonality determination was applied to feline intestinal lymphoplasmacytic inflammatory bowel disease (IBD) (9 cats), and transmural and mucosal T cell lymphoma (28 cats). Clonal rearrangement of the TCRG V--J junction was detected in 22 of 28 intestinal T cell lymphomas, and oligoclonality was detected in 3 intestinal T cell lymphomas. This contrasted with the detection of polyclonal rearrangement in normal intestinal tissues (3 cats) and in lymphoplasmacytic IBD (9 cats). It is proposed that assessment of TCRG V--J junctional diversity for the detection of clonality represents an important adjunctive tool for the diagnosis of T cell lymphoma in the cat.

Morphologic, immunohistochemical, and molecular characterization of hepatosplenic T-cell lymphoma in a dog

A 13-year-old neutered male Jack Russell Terrier (Parson Russell Terrier) was presented to the Texas Veterinary Medical Center with a history of lethargy, depression, vomiting, and fever. The dog had mildly regenerative anemia, severe thrombocytopenia and low antithrombin activity. Marked splenomegaly was found on physical examination and imaging studies, and malignant round cell neoplasia and marked extramedullary hematopoiesis were diagnosed on aspirates of the spleen. The dog underwent exploratory laporatomy and splenectomy. Because of a rapid decline in clinical condition postsurgery, the dog was euthanized. Splenic and hepatic biopsies were submitted for histopathologic evaluation. A neoplastic population of round cells was found throughout the splenic parenchyma and within hepatic sinusoids. The neoplastic cells stained strongly positive for CD3 (T-cell marker) and were negative for CD79a (B-cell marker) and lysozyme (histiocytic marker). A diagnosis of T-cell lymphoma was confirmed by assessment of T-cell clonality using canine-specific polymerase chain reaction-based techniques. Although expression of the gammadelta T-cell receptor was not evaluated, this case shares many similarities with a rare syndrome in humans known as hepatosplenic gammadelta T-cell lymphoma.

Molecular methods to distinguish reactive and neoplastic lymphocyte expansions and their importance in transitional neoplastic states

Although lymphoma and leukemia usually can be diagnosed by routine cytology and histology, some cases present a diagnostic challenge for pathologists and clinicians. Often the dilemma lies in determining whether a population of lymphocytes is reactive or neoplastic. We review currently available methods for analyzing lymphocyte populations by immunophenotyping and by identifying clonally rearranged immunoglobulin and T-cell receptor genes and discuss how these tests can be used to clarify such diagnostic dilemmas. We also describe the detection of chromosomal abnormalities and methods on the horizon, such as gene expression profiling, to identify diagnostically useful oncogenes. Finally, we review the emerging concept of transitional neoplastic states, in which reactive lymphocytes transform to neoplastic lymphocytes in the presence of continued antigenic stimulation, such as that caused by infection with Helicobacter pylori. The existence of transitional neoplastic states underscores the need for an array of molecular diagnostic tools that would improve our ability to characterize lymphocyte populations in human and animal patients and enhance early detection of neoplastic lymphocytes such that eradication of the infectious or inflammatory stimulus could lead to cure.

Detection of neoplastic lymphocytes in peripheral blood of dogs with lymphoma by polymerase chain reaction for antigen receptor gene rearrangement

BACKGROUND

Uniquely rearranged immunoglobulin and T-cell receptor gene sequences can be amplified and electrophoretically separated by size to detect a clonal population of lymphocytes.

OBJECTIVE

The purpose of this study was to determine whether the polymerase chain reaction (PCR) detects neoplastic (clonal) lymphocytes more frequently than do microscopic methods.

METHODS

We identified neoplastic lymphocytes in peripheral blood by both routine and standardized microscopic examination of blood smears and by PCR amplification of blood-derived DNA and compared the 3 methods for frequency of detection of leukemic involvement. For standardized microscopic examination (200 leukocytes counted on Wright-Giemsa-stained blood smears), samples were categorized as negative (</=1% prolymphocytes), equivocal (>1% prolymphocytes, no lymphoblasts), or positive (>/=1 lymphoblast). A PCR-amplified sample was positive if 1 or 2 discrete bands were seen on the gel, or negative if no bands, a smear, or a faint ladder was seen.

RESULTS

Using PCR, neoplastic lymphocytes were detected in peripheral blood 2.5 times more frequently than with routine or standardized microscopic evaluation. Eighty-three percent of samples negative by microscopy were positive by PCR.

CONCLUSION

PCR is more sensitive than microscopy for the detection of clonal lymphocytes in peripheral blood. The results of this study also suggest that neoplastic lymphocytes circulate in peripheral blood at a higher frequency than previously reported. PCR may be useful for detecting or phenotyping lymphoma, monitoring response to therapy, identifying recurrence, and screening breeds at risk.

Nodular immunocyte-derived (AL) amyloidosis in the trachea of a dog

A 7-year-old castrated male Miniature Schnauzer was examined because of labored breathing and episodes of respiratory distress that progressed to collapse. On cervical radiographs, a focal soft tissue mass in the caudal cervical portion of the trachea was observed, and during tracheoscopy, a 1 x 1 cm, pedunculated, multinodular, pink, intraluminal mass extending from the dorsal tracheal membrane and obstructing approximately 80% of the tracheal lumen was seen. Tracheal resection and anastomosis was performed to remove the mass, and the dog recovered without complications. On histologic examination, the mass consisted of a large accumulation of homogeneous, faintly fibrillar eosinophilic material admixed with a predominantly plasma cell infiltrate; examination of sections stained with thioflavin T and Congo red stain confirmed that the eosinophilic material was amyloid. A diagnosis of nodular, immunocyte-derived (AL) amyloidosis was made. Seventeen months after surgery, the dog had a relapse of respiratory distress because of an extramedullary plasmacytoma involving the trachea.

Clinical assessment of leukocytosis: distinguishing leukocytoses caused by inflammatory, glucocorticoid, physiologic, and leukemic disorders or conditions

The four major types of leukocytoses are inflammatory, glucocorticoid-associated, catecholamine-associated, and neoplastic. These leukocytoses are distinguished by leukocyte concentrations, microscopic features of leukocytes, and associations with other laboratory data. All laboratory findings need to be interpreted within the context of the case information, including signalment, history, and physical examination findings. Newer assays are being used to differentiate the different forms of leukocyte neoplasia and to distinguish between hyperplastic and neoplastic proliferations.

Chronic lymphocytic leukemia in dogs and cats: the veterinary perspective

Chronic lymphocytic leukemia (CLL) in dogs and cats shares many similarities with its human counterpart but also has significant differences. In marked contrast to people, CLL in dogs and cats is primarily a T-lymphocyte proliferation. Cytotoxic T-cell proliferations with granular lymphocyte morphology predominate in dogs, and T helper cell proliferations seem to be most common in cats with CLL. Immunophenotyping and assessment of clonality by molecular genetic analysis are newer adjunctive tools in veterinary medicine that are useful in the characterization and diagnosis of CLL in dogs and cats. The clinical presentation, typical hematologic findings, diagnosis, course of disease, prognosis, and therapy of CLL in dogs and cats are discussed.

Use of the Cell-Dyn 3500 to predict leukemic cell lineage in peripheral blood of dogs and cats

BACKGROUND

Morphology and cytochemistry are the foundation for classification of leukemias in dogs and cats. Advances in automated hematology instrumentation, immunophenotyping, cytogenetics, and molecular biology are significantly improving our ability to recognize and classify spontaneous myeloproliferative and lymphoproliferative disorders.

OBJECTIVE

The purpose of this study was to assess the utility of flow cytometry-based light scatter patterns provided by the Cell-Dyn 3500 (CD3500) automated hematology analyzer to predict the lineage of leukemic cells in peripheral blood of dogs and cats.

METHODS

Leukemic cells from 15 dogs and 6 cats were provisionally classified using an algorithm based on the CD3500 CBC output data and were subsequently phenotyped by enzyme cytochemistry, immunocytochemistry, indirect flow cytometry, and analysis of antigen receptor gene rearrangement.

RESULTS

The algorithm led to correct predictions regarding the ontogeny of the leukemic cells (erythroid/megakaryocytic potential, myeloid leukemia, monocytic leukemia, chronic granulocytic leukemia, lymphoid leukemia) in 19/21 animals. Mismatches in the WBC impedance count and the WBC optical count in conjunction with microscopic assessment of blasts in the blood were useful for predicting myeloproliferative disorders with erythroid or megakaryocytic potential. The leukocyte light scatter patterns enabled distinction among myeloid leukemias (represented by acute myelomonocytic leukemia, acute monocytic leukemia, chronic granulocytic leukemia) and lymphocytic leukemias (including acute and chronic lymphocytic leukemias). One case of acute lymphocytic leukemia was misidentified as chronic lymphocytic leukemia.

CONCLUSIONS

Algorithmic analyses can be applied to data generated by the CD3500 to predict the ontogeny of leukemic cells in the peripheral blood of dogs and cats. This rapid and quantitative technique may be used to improve diagnostic decisions, expand therapeutic choices, and increase prognostic accuracy.