Canine Indolent Nodular Lymphoma

Extranodal follicular lymphoma in the lung of a free-ranging red deer (Cervus elaphus)

A hunted free-ranging female red deer (Cervus elaphus) from a region near the Nahuel Huapi National Park, Northern Patagonia, Argentina, had a focally extensive peribronchial lymphoid proliferative lesion in the lung characterized by formation of multiple follicles, with prominent germinal centers lacking mantle zone cells and antigen-related polarity. On examination of immunohistochemically stained tissues, a predominance of B cells (cluster of differentiation [CD]20 positive) with only a few scattered T cells (CD3 positive) were present. The histologic and immunohistochemical characteristics are consistent with follicular lymphoma, which is frequently seen in human beings and less frequently in domestic animals.

Molecular profiling reveals prognostically significant subtypes of canine lymphoma

We performed genomewide gene expression analysis of 35 samples representing 6 common histologic subtypes of canine lymphoma and bioinformatics analyses to define their molecular characteristics. Three major groups were defined on the basis of gene expression profiles: (1) low-grade T-cell lymphoma, composed entirely by T-zone lymphoma; (2) high-grade T-cell lymphoma, consisting of lymphoblastic T-cell lymphoma and peripheral T-cell lymphoma not otherwise specified; and (3) B-cell lymphoma, consisting of marginal B-cell lymphoma, diffuse large B-cell lymphoma, and Burkitt lymphoma. Interspecies comparative analyses of gene expression profiles also showed that marginal B-cell lymphoma and diffuse large B-cell lymphoma in dogs and humans might represent a continuum of disease with similar drivers. The classification of these diverse tumors into 3 subgroups was prognostically significant, as the groups were directly correlated with event-free survival. Finally, we developed a benchtop diagnostic test based on expression of 4 genes that can robustly classify canine lymphomas into one of these 3 subgroups, enabling a direct clinical application for our results.

Histologic and immunohistochemical review of splenic fibrohistiocytic nodules in dogs

BACKGROUND

Splenic fibrohistiocytic nodules (SFHN) are commonly diagnosed. It is suspected that these represent a heterogeneous group of malignant and nonmalignant diseases, separation of which could improve the ability of clinicians to prognosticate for dogs.

HYPOTHESIS/OBJECTIVES

Immunohistochemistry will differentiate histologic diagnoses within the group of SFHN; survival after splenectomy is associated with those histologic types.

ANIMALS

Thirty-two dogs with SFHN treated by or under direction from veterinary oncologists.

METHODS

Retrospective case record analysis from dogs followed from splenectomy until death. Clinical, histopathologic, and immunohistochemistry data analyzed for an association with survival time.

RESULTS

Thirty-two dogs had SFHN; grade 1 (2 dogs), grade 2 (9 dogs), and grade 3 (lymphoid percentage <40%; 21 dogs). Twenty-two dogs died, 10 were censored (9 alive median of 883 days after splenectomy). Median overall survival was 387 days, and grade 3 SFHN was negatively [corrected] associated with survival time as previously reported (P < .001). Of 31 available samples, dogs had diseases reclassified as nodular hyperplasia (13; 8 complex, 5 lymphoid including 2 marginal zone), lymphoma (4; 2 marginal zone lymphoma, 1 high grade B-cell lymphoma, and 1 marginal zone transitional to high grade B-cell lymphoma), 8 stromal sarcomas, and 6 histiocytic sarcomas. Dogs with histiocytic sarcoma had worse survival (median 74 days) than dogs with other diseases.

CONCLUSIONS AND CLINICAL IMPORTANCE

Splenic histiocytic sarcoma is an aggressive disease; however, some dogs with stromal sarcomas had long survival times. The term SFHN is no longer warranted for this group of disorders.

Two Hundred Three Cases of Equine Lymphoma Classified According to the World Health Organization (WHO) Classification Criteria

Lymphoma is the most common malignant neoplasm in the horse. Single case reports and small retrospective studies of equine lymphomas are reported infrequently in the literature. A wide range of clinical presentations, tumor subtypes, and outcomes have been described, and the diversity of the results demonstrates the need to better define lymphomas in horses. As part of an initiative of the Veterinary Cooperative Oncology Group, 203 cases of equine lymphoma have been gathered from 8 institutions. Hematoxylin and eosin slides from each case were reviewed and 187 cases were immunophenotyped and categorized according to the World Health Organization classification system. Data regarding signalment, clinical presentation, and tumor topography were also examined. Ages ranged from 2 months to 31 years (mean, 10.7 years). Twenty-four breeds were represented; Quarterhorses were the most common breed ( n = 55), followed by Thoroughbreds ( n = 33) and Standardbreds ( n = 30). Lymphomas were categorized into 13 anatomic sites. Multicentric lymphomas were common ( n = 83), as were skin ( n = 38) and gastrointestinal tract ( n = 24). A total of 14 lymphoma subtypes were identified. T-cell–rich large B-cell lymphomas were the most common subtype, diagnosed in 87 horses. Peripheral T-cell lymphomas ( n = 45) and diffuse large B-cell lymphomas ( n = 26) were also frequently diagnosed.

The dog as a possible animal model for human non-Hodgkin lymphoma: a review

Lymphoma represents the most frequent hematopoietic cancer in dogs, and it shows significant overlap with the human disease. Several environmental factors have been associated with canine lymphoma, suggesting that they may contribute to lymphomagenesis. Canine lymphoma often presents in advanced stage (III-V) at diagnosis and, most commonly, has an aggressive clinical course requiring prompt treatment, which relies on the use of polychemotherapy. In this review, we will summarize the state-of-the-art of canine lymphoma epidemiology, pathobiology, diagnostic work-up and therapy, and will highlight the links to the corresponding human disease, providing evidence for the use of dog as an animal model of spontaneous disease.

Diagnostic evaluation and treatment recommendations for dogs with substage-a high-grade multicentric lymphoma: results of a survey of veterinarians

The goal of this study was to survey veterinarians regarding their current initial diagnostic and treatment recommendations for dogs with substage-a high-grade multicentric lymphoma. A written survey was conducted at the 2009 Veterinary Cancer Society conference asking veterinarians to provide demographic information, initial staging diagnostics and treatment recommendations for canine lymphoma. The most commonly recommended staging diagnostics were complete blood count (100%), chemistry panel (100%), urinalysis (85%), lymph node cytology (88%), thoracic radiographs (84%), immunophenotyping (76%) and abdominal ultrasound (75%). The most commonly used first-line B-cell protocols combined the drugs L-asparaginase, cyclophosphamide, doxorubicin, vincristine and prednisone (L-CHOP, 51%). CHOP (30%) and other CHOP-based protocols (12%) were used as well. Thirty-one percent of responders treated B- and T-cell lymphomas differently. Protocol lengths varied from ≤ 16 weeks to >2 years. Current staging and treatment recommendations for canine lymphoma are varied. Efforts to standardize recommendations should be considered.

Canine intravascular lymphoma with overt leukemia

A 6-year-old spayed Labrador Retriever Mix dog was evaluated for a 2-week history of progressive generalized weakness and reluctance to stand. Physical examination revealed severe weakness with obtunded mentation, head tilt, bilateral nystagmus, and decreased vision. CBC findings included mild nonregenerative anemia, marked thrombocytopenia, and a few atypical mononuclear cells on the blood film. The cells were 15-30 μm in diameter and had round to oval to reniform centrally placed nuclei with stippled chromatin, prominent nucleoli, and abundant basophilic cytoplasm with numerous discrete vacuoles and, occasionally, small azurophilic granules. Similar cells were found in bone marrow. On histologic examination of tissues collected at necropsy, neoplastic cells were detected in bone marrow, hepatic sinusoids, cerebral and meningeal vessels, and in capillaries of the heart, renal interstitium, small intestinal submucosa, and muscularis, and alveolar septa. A small discrete mass in the right atrium consisted of similar neoplastic cells, and the spleen was diffusely infiltrated. Tissue distribution was suggestive of intravascular lymphoma. Neoplastic cells in tissue sections were immunoreactive for vimentin, CD18, CD45, and granzyme B and lacked immunoreactivity for cytokeratin. Neoplastic cells on bone marrow aspirate smears and blood films lacked immunoreactivity for CD3, CD79a, CD1c, CD11b, CD11c, CD11d, and E-cadherin. In the absence of immunophenotypic evidence for the neoplastic cells being derived from B-cell, T-cell, or histocytic/dendritic lineages and the lack of clonal antigen receptor gene rearrangement(s), along with positive immunoreactivity for granzyme B, a tumor of NK cells was considered likely. Based on current knowledge, this is the first report of canine intravascular lymphoma, of probable NK cell origin, with peripheral blood involvement.

A novel clonality assay for the assessment of canine T cell proliferations

Polymerase chain reaction (PCR) based clonality assays are an important tool to differentiate neoplastic from reactive lymphocyte populations. A recent description of the canine T cell receptor γ locus identified a large number of formerly unknown genes, and determined the locus topology consisting of 8 cassettes with up to 3 variable (V) genes, 2 joining (J) genes and one constant (C) gene each. Given that these data were not available when existing canine T cell clonality assays were developed, it is likely that they will fail to detect a subset of clonal lymphocyte populations. The objective of this study was to gauge the potential of canine T cell clonality assays to detect all rearranged T cell receptor γ genes and to develop an improved clonality assay. The primer sequences of existing clonality assays were aligned to the reference sequences of all rearranged genes and genes were scored as to the likelihood of being recognized by a primer. All four assays likely recognized subgroup Vγ2 and Vγ6 genes but 3 out of 4 assays were unlikely to detect subgroup Vγ3 and Vγ7 genes. All assays likely recognized Jγx-2 genes, but only two assays were likely to detect most Jγx-1 genes. Two assays had forward primers located as close as four nucleotides to the junctional region. A new multiplex PCR was designed with all primers combined in a single tube. An alternative primer set allowed identification of variable gene usage through gene specific forward primers. The coverage of all rearranged genes facilitated the detection of multiple clonal rearrangements per neoplastic sample. The new assay detected clonal DNA at a concentration of 5% within polyclonal background but detection thresholds were dependent on the gene usage of clonal rearrangements as well as the position of the clonal peak in respect to the polyclonal background. The new multiplex assay recognized 12/12 (100%) of confirmed neoplastic samples as compared to 2/12 (17%) by an existing assay. On a series of 60 diagnostic samples the concordance rate of both assays was 41/60 (68.3%). In 14/60 (23.3%) of the cases, the new multiplex assay yielded a clonal result while the existing assay gave a non-clonal result. In 5/60 (8.3%) of cases, the new assay yielded a non-clonal result while the existing primer set gave a clonal result. These findings suggest that the new multiplex assay has an improved sensitivity over traditional assays and is suited to reduce the rate of false-negative results.

Development and characterization of 5 canine B-cell lymphoma cell lines

Canine and human lymphoma share similar characteristics in disease development and response to therapy. Translational research can be furthered using tools such as canine cell lines to model therapeutic compounds and strategies. We developed 5 B-cell lymphoma cell lines from dogs with confirmed large B-cell lymphoma. These cell lines were CD3, CD18, CD20, and CD90 positive with variable CD79a, CD1c and CD34 expression. All cell lines were tumorigenic in Nu/nu mice and were wild type for p53. Canine lymphoma cell lines serve as an important resource for translational lymphoma research.

Successful management with CHOP for pulmonary lymphomatoid granulomatosis in a dog

A 3-year-old, spayed female miniature dachshund was presented for vomiting and anorexia. Thoracic radiographs and CT scan revealed abnormal pulmonary opacities at bilateral caudal lobe. Cytological analysis of the pulmonary mass revealed the presence of large lymphohistiocytic cells and small lymphocytes with occasional neutrophils and plasma cells. An open lung biopsy was performed and a diagnosis of pulmonary lymphomatoid granulomatosis (LYG) was made. The dog was administered CHOP based therapy (modified UW-25), and it survived for 1,022 days after admission. Immunohistochemistry revealed pulmonary lesions consisted of many CD79a positive B cells aggregation and proliferation with prominent angiocentric pattern. This was the first case of canine pulmonary LYG managed by CHOP chemotherapy.

Heteroduplex polymerase chain reaction is essential for canine receptor rearrangement analysis

Polymerase chain reaction (PCR) for antigen receptor rearrangement is a sensitive technique for detecting lymphocyte-proliferative disorders, but it tends to produce false-positive results, a phenomenon termed pseudoclonality. Heteroduplex analysis, which is useful to distinguish clonal reactions from pseudoclonal ones in dogs, can be applied to avoid misdiagnosis and determine the reliability of results. In the current study, PCR for antigen receptor rearrangement was used to identify clonal proliferation of lymphocytes in duodenal and lymphoid tissue from dogs presenting with chronic vomiting and enlarged peripheral lymph nodes typical of multicentric lymphoma, and the test results were verified with heteroduplex analysis. In the case of almost all of the duodenal samples, even without a histologic diagnosis of lymphoma, a distinct band similar to that observed in the case of lymphoma was obtained for both B- and T-cell clonality. All of the bands obtained from the nonneoplastic duodenum disappeared following heteroduplex analysis of the PCR product, whereas the distinct bands from the lymphoma remained. In the lymph node samples, the pseudoclonal bands that disappeared in the heteroduplex analysis were detected mainly in B cells. In conclusion, heteroduplex analysis with PCR for antigen receptor rearrangement is a suitable tool for diagnosing canine lymphoma and decreasing the possibility of misdiagnosis of pseudoclonality.

Classification of canine malignant lymphomas according to the World Health Organization criteria

A study was carried out to test the accuracy and consistency of veterinary pathologists, not specialists in hematopathology, in applying the World Health Organization (WHO) system of classification of canine lymphomas. This study represents an initiative of the ACVP Oncology Committee, and the classification has been endorsed by the World Small Animal Veterinary Association (WASVA). Tissue biopsies from cases of canine lymphoma were received from veterinary oncologists, and a study by pathologists given only signalment was carried out on 300 cases. Twenty pathologists reviewed these 300 cases with each required to choose a diagnosis from a list of 43 B and T cell lymphomas. Three of the 20 were hematopathologists who determined the consensus diagnosis for each case. The 17 who formed the test group were experienced but not specialists in hematopathology, and most were diplomates of the American or European Colleges of Veterinary Pathology. The overall accuracy of the 17 pathologists on the 300 cases was 83%. When the analysis was limited to the 6 most common diagnoses, containing 80% of all cases, accuracy rose to 87%. In a test of reproducibility enabled by reintroducing 5% of cases entered under a different identity, the overall agreement between the first and second diagnosis ranged from 40 to 87%. The statistical review included 43,000 data points for each of the 20 pathologists.

Transferrin receptor expression in canine lymphoma

Transferrin receptor 1 (TfR1) expression was measured by immunohistochemistry in 78 archived cases of canine B-cell and T-cell lymphoma with an anti-human TfR1 monoclonal antibody that was validated in the dog by immunohistochemistry and immunoblotting. The canine lymphoma cases were initially classified on the basis of World Health Organization criteria and then subdivided into the following 4 subgroups: low-grade B-cell (LGB), high-grade B-cell (HGB), low-grade T-cell (LGT), and high-grade T-cell (HGT). A visual scoring system and densitometric analysis of the proportion and intensity of positive staining were used to quantify TfR1 expression. TfR1 expression was also correlated to mitotic rate. TfR1 expression was significantly lower in the LGT tumors compared to all other lymphoma subgroups (LGB, HGB, and HGT). LGB tumors showed a TfR1 expression similar to those of the high-grade tumors (HGB and HGT). Significant correlations were found between mitotic rate and densitometric TfR1 variables in the T-cell tumors but not in the B-cell tumors. Further studies are needed to investigate the underlying molecular basis of the high TfR1 expression in LGB lymphomas and its pathological relevance. The anti-human TfR1 monoclonal antibody is a useful tool for measurement of total cellular transferrin receptor expression in the dog; however, an antibody with specificity for the canine TfR1 ectodomain is needed to investigate the potential of this receptor as an oncolytic target.

A Morphological Study of 608 Cases of Canine Malignant Lymphoma in France With a Focus on Comparative Similarities Between Canine and Human Lymphoma Morphology

This study reports cytomorphological, histomorphological, and immunological characterization of 608 biopsy cases of canine malignant lymphoma, with epidemiological and clinical data, collected from 7 French veterinary pathology laboratories. It compares morphological characteristics of malignant lymphoma in canines, per the updated Kiel classification system, with those reported in humans, per the World Health Organization (WHO) classification system. Of tumors described, 24.5% and 75.5% were classified as low- and high-grade malignant lymphomas, respectively. Presenting clinical signs included generalized or localized lymphadenopathy (82.4%) and extranodal diseases (17.6%) involving the skin (12.34%) and other sites (5.26%). Immunohistochemistry confirmed 63.8% B-cell (CD3–, CD79a+), 35.4% T-cell (CD3+, CD79a–), and 0.8% null-cell (CD3–, CD79a–) lymphomas. Most B-cell cases (38.49%) were of high-grade centroblastic polymorphic subtype; most T-cell cases (8.55%), high-grade pleomorphic mixed and large T-cell lymphoma subtypes. Some B-cell tumors showed morphologic characteristics consistent with follicular lymphomas and marginal zone lymphomas per the Revised European American Classification of Lymphoid Neoplasms and WHO canine classification systems and the WHO human classification system. Unusual high-grade B-cell subtypes included an atypical high-grade small B-cell lymphoma (0.66%), Burkitt-type B-cell lymphoma (1.64%), plasmacytoid lymphoma (0.99%), and mediastinal anaplastic large B-cell lymphoma (0.16%). Unusual T-cell subtypes included a previously undescribed high-grade canine immunoblastic T-cell type (1.15%), a rare low-grade prolymphocytic T-cell lymphoma (0.16%), and a recently described high-grade canine T-cell entity—aggressive granulocytic large-cell lymphoma (0.16%). Marginal zone lymphomas were common (10.86%); follicular lymphomas were rare (0.49%). Canine primary cutaneous malignant lymphoma subtypes were present (11.84%). There was no significant difference between B- and T-cell malignant lymphoma in regard to canine age and sex. A significant overrepresentation of Boxers (24.19%) was found for T-cell lymphomas.

Eosinophilia and eosinophilic infiltration into splenic B-cell high-grade lymphoma in a dog

A 13-year-old mixed-breed dog showing ascites, anorexia and anemia was found to have leukocytosis with marked eosinophilia, splenomegaly and hepatomegaly. The dog died 4 days after initial presentation and was diagnosed with splenic high-grade B-cell lymphoma at necropsy. Remarkable infiltrations of eosinophils were observed in spleen and liver tissues. The eosinophilia and infiltration of eosinophils into the lesions could have been associated with B-cell lymphoma because causes other than lymphoma were excluded. This is the first report of eosinophilia and eosinophilic infiltrations into neoplastic lesions in a dog with high-grade B-cell lymphoma.

A case of canine lymphomatoid granulomatosis with cutaneous lesions

A 10-year-old, castrated, mixed-breed dog presented with a 1.5-month history of scattered, crateriform ulcers on the trunk and extremities. Some skin lesions appeared to regress spontaneously, but new lesions developed. Thoracic radiography revealed pulmonary consolidated lesions suggestive of tumor. A skin biopsy was performed for histopathological, immunohistochemical and clonality analyses. Histopathological examination of the cutaneous lesion revealed an intense infiltration of atypical lymphoid cells with some other cell populations around the blood vessels in the dermis. Atypical lymphoid cells were shown to be CD3-positive in the immunohistochemical analysis. The presence of clonally expanded T-cells was revealed by the clonal rearrangement of T-cell receptor gamma-chain gene. From the above findings, the dog was diagnosed with lymphomatoid granulomatosis.

Hormonal and sex impact on the epidemiology of canine lymphoma

The Surveillance Epidemiology and End Results data demonstrate that the risk of non-Hodgkin lymphoma is lower for women, but that the incidence increases after fifty years of age, at which menopause is regularly reached, suggesting that female hormones may be protective for NHL. This study examines the influence of sex on lymphoma risk in a relevant large animal model. Records for dogs in the Veterinary Medical Database were analyzed from 1964 to 2002. Risk ratios were calculated to evaluate associations between sex, neutering status, and lymphoma occurrence. A total of 14,573 cases and 1,157,342 controls were identified. Intact females had a significantly lower risk of developing lymphoma, Odds Ratio 0.69 (0.63–0.74) with a P < .001. We conclude that there is a sex effect on NHL risk in dogs similar to humans. We hypothesize that the hormone levels of intact females lower the risk of NHL. The possibility of a protective role of endogenous estrogens in the etiology of NHL should be investigated.

Leading the way: canine models of genomics and disease

In recent years Canis familiaris, the domestic dog, has drawn considerable attention as a system in which to investigate the genetics of disease susceptibility, morphology and behavior. Because dogs show remarkable intrabreed homogeneity, coupled with striking interbreed heterogeneity, the dog offers unique opportunities to understand the genetic underpinnings of natural variation in mammals, a portion of which is disease susceptibility. In this review, we highlight the unique features of the dog, such as population diversity and breed structure, that make it particularly amenable to genetic studies. We highlight recent advances in understanding the architecture of the dog genome, which propel the system to the forefront of consideration when selecting a system for disease gene studies. The most notable benefit of using the dog for genetic studies is that dogs get many of the same diseases as humans, with a similar frequency, and the same genetic factors are often involved. We discuss two approaches for localizing disease genes in the dog and provide examples of ongoing studies.

Long term survival of primary skeletal muscle lymphoma in a miniature dachshund

An 8-year-old miniature dachshund presented with a right femoral muscle mass and anorexia. Cytology of the mass revealed a number of small-sized lymphoid cells containing a pleomorphic-shaped dense nucleus and narrow pale cytoplasm. Histopathology indicated that neoplastic lymphoid cells proliferated in skeletal muscles and replaced the muscular architecture. Immunohistochemical and genetic examinations confirmed the diagnosis of primary skeletal muscle lymphoma classified as the pleomorphic small cell type and T-cell low-grade. Although the dog suffered at least three relapses by combination chemotherapy, the dog survived 713 days after the initial presentation.

Hypermethylation of the DLC1 CpG island does not alter gene expression in canine lymphoma

Background

This study is a comparative epigenetic evaluation of the methylation status of the DLC1 tumor suppressor gene in naturally-occurring canine lymphoma. Canine non-Hodgkin's lymphoma (NHL) has been proposed to be a relevant preclinical model that occurs spontaneously and may share causative factors with human NHL due to a shared home environment. The canine DLC1 mRNA sequence was derived from normal tissue. Using lymphoid samples from 21 dogs with NHL and 7 normal dogs, the methylation status of the promoter CpG island of the gene was defined for each sample using combined bisulfite restriction analysis (COBRA), methylation-specific PCR (MSP), and bisulfite sequencing methods. Relative gene expression was determined using real-time PCR.

Results

The mRNA sequence of canine DLC1 is highly similar to the human orthologue and contains all protein functional groups, with 97% or greater similarity in functional regions. Hypermethylation of the 5' and 3' flanking regions of the promoter was statistically significantly associated with the NHL phenotype, but was not associated with silencing of expression or differences in survival.

Conclusion

The canine DLC1 is constructed highly similarly to the human gene, which has been shown to be an important tumor suppressor in many forms of cancer. As in human NHL, the promoter CpG island of DLC1 in canine NHL samples is abnormally hypermethylated, relative to normal lymphoid tissue. This study confirms that hypermethylation occurs in canine cancers, further supporting the use of companion dogs as comparative models of disease for evaluation of carcinogenesis, biomarker diagnosis, and therapy.

Immunophenotyping and gene rearrangement analysis in dogs with lymphoproliferative disorders characterized by small-cell lymphocytosis

Lymphocytosis caused by neoplastic proliferation of small lymphocytes is occasionally difficult to distinguish by morphological examination from nonneoplastic lymphocytosis. To examine the clinical utility of gene rearrangement analysis for demonstrating neoplastic proliferation of small lymphocytes, gene rearrangement analysis was performed in comparison with immunophenotyping using peripheral lymphocytes in dogs with small lymphocytosis. Thirty-one dogs with small-cell lymphocytosis (8,100-884,300/microl) were enrolled. By immunophenotyping, lymphocytosis of all dogs was suggested to be neoplastic in nature based on the detection of marked expansion of phenotypically homogeneous lymphocytes or the presence of an aberrant antigen-expressing population of lymphocytes. In contrast, gene rearrangement analysis represented clonality in 27 dogs (detection rate of 87%). From the present study, gene rearrangement analysis was considered to be worthwhile to strengthen the evidence of neoplastic proliferation of small lymphocytes when coupled with immunophenotyping and to be a suitable diagnostic substitute if immunophenotyping is not available in clinical practice.

Immunophenotypic and Histologic Classification of 50 Cases of Feline Gastrointestinal Lymphoma

The purpose of this study was to determine the immunophenotype and histologic classification of 50 cases of feline gastrointestinal lymphoma. Classification was determined using the National Cancer Institute Working Formulation and the Revised European and American Lymphoma/ World Health Organization classification system. Tissue sections were stained with HE, phosphotungstic acid hematoxylin, anti-CD3, anti-CD79a, and anti-BLA.36. Overall, B-cell tumors predominated at 54% (27/50), including 16 diffuse large with immunoblastic nuclear type, 2 diffuse large with centroblastic nuclear type, 3 small lymphocytic, 4 lymphocytic intermediate type, and 2 T-cell-rich large B-cell lymphomas. T-cell tumors comprised 38% (19/50), including 15 epitheliotropic small lymphocytic and 4 lymphoblastic. Three tumors (6%) were nonreactive for B- and T-cell markers and had eosinophilic cytoplasmic granules when stained with HE. Gastric tumors were diagnosed in 24% (12/50) of cats, and 18% (9/50) were present only in the stomach. All gastric lymphomas were of B-cell lineage. Small intestinal lymphoma predominated, with 74% (37/50) of cats affected: T-cell tumors comprised 52% (19/37); 38% (14/37) were B-cell tumors; 8% (3/37) were nonreactive for B- and T-cell markers; and 2% (1/37) expressed both CD3 and BLA.36. Of the 8 cats (16%) that had lymphoma of the large intestine, 88% (7/8) had B-cell tumors and 12% (1/8) had T-cell tumors. The strongest association between gastrointestinal lymphoma immunophenotype, histologic classification, and location occurred in the stomach, where there was a predominance of diffuse large B-cell lymphoma of immunoblastic nuclear type.

Immunophenotypic and cytomorphologic subclassification of T-cell lymphoma in the boxer breed

The boxer breed is at high risk for developing lymphoma and, in contrast to the general canine population, is predisposed to the T-cell variant of the disease. The purpose of this study was to more accurately classify lymphoma in this breed. Clinical, cytomorphologic and immunophenotypic data were examined in 43 boxers with lymphoma. Twenty-five cases were collected prospectively and a further 18 cases were obtained retrospectively. Lymphomas were classified as multicentric (n=29), mediastinal (n=6) and intestinal (n=8). Of the 40 immunophenotyped samples, 34 (85%) were T-cell, 5 (12.5%) were B-cell and 1 was a non-B-cell non-T-cell lymphoma. Immunophenotypic subtyping was done on prospectively collected T-cell lymphoma samples (n=22) to differentiate CD4 (helper) from CD8 (cytotoxic) T-cell origin as well as to determine the T-cell receptor (TCR) expression (TCRalphabeta vs. TCRdeltagamma). Phenotypic expression was CD4+ (n=12), double negative (DN) (n=6), double positive (DP) (n=1) and CD8+ (n=1), respectively, while two samples had no interpretable result. 20/22 samples were TCRalphabeta+ with only 1 sample being TCRdeltagamma+ and 1 with no interpretable result. Cytomorphologic analysis was done on the same 22 samples using the World Health Organization (WHO) classification scheme. According to this scheme, 17/22 samples were classified as lymphoblastic, 2/22 as large cell peripheral T-cell lymphoma-not otherwise specified (PTCL-NOS), 2/22 as large granular lymphoma (LGL) high-grade and 1/22 as small lymphocytic. The results of this study indicate that lymphoma in the boxer breed is a disease comprised predominantly of TCRalphabeta+, CD4+ (helper) T-cells with lymphoblastic (high-grade) morphology.

Inactivation of the p16 cyclin-dependent kinase inhibitor in high-grade canine non-Hodgkin's T-cell lymphoma

The significance of p16/Rb tumor suppressor pathway inactivation in T-cell non-Hodgkin's lymphoma (NHL) remains incompletely understood. We used naturally occurring canine NHL to test the hypothesis that p16 inactivation has specific pathologic correlates. Forty-eight samples (22 T-cell NHL and 26 B-cell NHL) were included. As applicable, metaphase- or array-based comparative genomic hybridization, Southern blotting, promoter methylation, and Rb phosphorylation were used to determine the presence, expression, and activity of p16. Fisher's exact test was used to test for significance. Deletion of p16 (or loss of dog chromosome 11) was restricted to high-grade T-cell NHL (lymphoblastic T-cell lymphoma and peripheral T-cell lymphoma, not otherwise specified). These were characterized by a concomitant increase of tumor cells with Rb phosphorylation at canonical CDK4 sites. Rb phosphorylation also was seen in high-grade B-cell NHL (diffuse large B-cell lymphoma and Burkitt-type lymphoma), but in those cases, it appeared to be associated with c-Myc overexpression. The data show that p16 deletion or inactivation occurs almost exclusively in high-grade T-cell NHL; however, alternative pathways can generate functional phenotypes of Rb deficiency in low-grade T-cell NHL and in high-grade B-cell NHL. Both morphologic classification according to World Health Organization criteria and assessment of Rb phosphorylation are prognostically valuable parameters for canine NHL.