Feline eosinophilic sclerosing fibroplasia associated with T-/natural killer-cell lymphoma

Feline eosinophilic sclerosing fibroplasia (FESF) is a proliferative, inflammatory disease of the gastrointestinal tract and other sites, uncommonly diagnosed in the cat. This entity of uncertain etiology typically presents as a progressive mass lesion, mimicking a neoplastic process. In this case series, we present 17 cases of FESF associated with intralesional lymphoma. Histologic and immunohistochemical characterization of this unique lymphoma revealed that the neoplastic lymphocytes were immunopositive for CD56 and/ or CD3, suggesting a natural killer cell, natural killer T-cell, or T-cell origin. This case series represents the first description of this lymphoma subtype, for which the term eosinophilic sclerosing lymphoma is proposed.

Comparison of the accuracy of minimally invasive techniques (cytology, cell block, immunocytochemistry and clonality assay) in the diagnosis of canine multicentric lymphoma

Lymphoma ranks among the most prevalent neoplasms in veterinary oncology, frequently diagnosed in dogs, particularly in its multicentric form. While histopathology plays a crucial role in lymphoma diagnosis, prognosis and prediction of biological behavior, minimally invasive diagnostic methods are increasingly emerging as viable alternatives. This study aims to assess and compare various minimally invasive diagnostic techniques for multicentric lymphomas in dogs. A total of 38 dogs, encompassing various sexes, ages, and breeds, with clinical suspicion of multicentric lymphoma, was included in the study. Fine needle aspiration was employed to collect samples from lymph nodes, which were subsequently used for cytology, cell block preparation, PCR for antigen receptor rearrangement (PARR), and immunocytochemistry. Among the animals evaluated, 31 dogs received a cytological diagnosis of lymphoma, while 7 showed findings suggestive of lymphoma or lymphadenitis. Immunocytochemistry on cytological smears yielded inconclusive results in 50 % of cases, with 44.74 % diagnosed with B-cell lymphoma and 5.26 % with T-cell lymphoma. Cell block analysis identified lymphoma in 30 dogs and suggested lymphoma or a round cell neoplasm in 8 cases. Cell block immunocytochemistry confirmed lymphoma in 35 dogs, comprising 80 % B-cell and 20 % T-cell lymphomas. PARR revealed monoclonal rearrangement/clonality in 33 cases, with 84.85 % of these being B-cell and 15.15 % T-cell lymphomas. This study underscores the precision of minimally invasive techniques in diagnosing and characterizing multicentric lymphoma in dogs, reaffirming their significance in veterinary clinical practice.

Investigating comparative polymerase chain reaction for antigen receptor rearrangement analysis in different types of feline lymphoma samples

Cats have the highest incidence of lymphoma among all animal species. Lymphoma accounts for 41% of all malignant tumors in cats and is responsible for 90% of hematopoietic tumors in felines. Biopsies are considered the gold standard for diagnosis. Polymerase chain reaction (PCR)-based clonality assessment of antigen receptor gene rearrangements can be a valuable complementary tool for identifying infiltrating B-and T-lymphocyte clones. Many studies have focused on intestinal cases but few have addressed mediastinal lymphoma. This study aims to: (1) investigate the clonality patterns of lymphoma samples from various anatomical sites, with a particular focus on mediastinal lymphoma, and (2) evaluate the sensitivity and specificity of the clonality analysis of pleural effusion samples in comparison with cytology, histology, immunohistochemistry, and immunocytochemistry for diagnosing mediastinal lymphoma. There were 82 cases, divided into 49 formalin-fixed and paraffin-embedded biopsy specimens (FFPE), 22 cell pellets, and 11 fresh tissue. This study examined the sensitivity and specificity of PCR for antigen receptor rearrangement (PARR) compared to immunohistochemistry (IHC) and immunocytochemistry. For T-cell receptor gamma chain genes, PARR demonstrated a sensitivity of 58.33% for both fresh tissue and FFPE samples, with a specificity of 100%. Cell pellet analysis exhibited a sensitivity of 64.71% and maintained 100% specificity. A combined analysis of fresh tissue and FFPE with cell pellets showed a sensitivity of 62.07%. For IGH, the sensitivity for fresh tissue and FFPE samples was 56.25%, while cell pellet analysis showed a sensitivity of 62.50%. When considering fresh tissue and FFPE samples, the sensitivity was 57.14%. In conclusion, molecular techniques have emerged as valuable tools for detecting lymphoma, especially in cases where traditional diagnostic methods yield inconclusive results, such as mediastinal lymphoma. While biopsy may not always be feasible, cytology and cell pellets obtained from pleural effusion offer alternative immunocytochemistry and molecular analysis samples, provided they are of sufficient quality and quantity. All sample types considered in this study were suitable for PARR to aid in cases with inconclusive results. Therefore, the sample selection should be tailored to the clinical situation.

Fecal microbiota and concentrations of long-chain fatty acids, sterols, and unconjugated bile acids in cats with chronic enteropathy

Feline chronic enteropathies (FCE) are common causes of chronic gastrointestinal signs in cats and include different diseases such as food-responsive enteropathy (FRE), inflammatory bowel diseases (IBD), and low-grade intestinal T-cell lymphoma (LGITL). Although changes in intestinal microbiota and fecal metabolites have been reported in dogs and humans with chronic enteropathy, research in cats has been limited. Therefore, this study aimed to evaluate the fecal microbiota and lipid-related fecal metabolites in cats with FCE to a clinically healthy comparison group (CG). A total of 34 cats with FCE (13 FRE, 15 IBD, and 6 LGITL) and 27 cats in the CG were enrolled in this study. The fecal microbiota was evaluated by the qPCR-based feline Dysbiosis Index (DI). The feline DI in cats with CE (median: 1.3, range: -2.4 to 3.8) was significantly higher (p < 0.0001) compared to CG (median: - 2.3, Range: -4.3 to 2.3), with no difference found among the FCE subgroups. The fecal abundances of Faecalibacterium (p < 0.0001), Bacteroides (p < 0.0001), Fusobacterium (p = 0.0398), Bifidobacterium (p = 0.0004), and total bacteria (p = 0.0337) significantly decreased in cats with FCE. Twenty-seven targeted metabolites were measured by gas chromatography-mass spectrometry, including long-chain fatty acids (LCFAs), sterols, and bile acids (BAs). Fecal concentrations of 5 of 12 LCFAs were significantly increased in cats with FCE compared to CG. Fecal concentrations of zoosterol (p = 0.0109), such as cholesterol (p < 0.001) were also significantly increased in cats with FCE, but those of phytosterols were significantly decreased in this group. No differences in fecal BAs were found between the groups. Although no differences were found between the four groups, the fecal metabolomic pattern of cats with FRE was more similar to that of the CG than to those with IBD or LGITL. This could be explained by the mild changes associated with FRE compared to IBD and LGITL. The study showed changes in intestinal microbiota and alteration of fecal metabolites in FCE cats compared to the CG. Changes in fecal lipids metabolites suggest a dysmetabolism of lipids, including LCFAs, sterols, and unconjugated BAs in cats with CE.

Effects of fixation and demineralization on histomorphology and DNA amplification of canine bone marrow

Fixation and demineralization protocols for bone marrow (BM) across diagnostic laboratories are not standardized. How different protocols affect histomorphology and DNA amplification is incompletely understood. In this study, 2 fixatives and 3 demineralization methods were tested on canine BM samples. Twenty replicate sternal samples obtained within 24 hours of death were fixed overnight in either acetic acid-zinc-formalin (AZF) or 10% neutral-buffered formalin (NBF) and demineralized with formic acid for 12 hours. Another 53 samples were fixed in AZF and demineralized with hydrochloric acid for 1-hour, formic acid for 12 hours, or ethylenediamine tetraacetic acid (EDTA) for 24 hours. Histologic sections were scored by 4 raters as of insufficient, marginal, good, or excellent quality. In addition, DNA samples extracted from sections treated with the different fixation and demineralization methods were amplified with 3 sets of primers to conserved regions of T cell receptor gamma and immunoglobulin heavy chain genes. Amplification efficiency was graded based on review of capillary electrophoretograms. There was no significant difference in the histomorphology scores of sections fixed in AZF or NBF. However, EDTA-based demineralization yielded higher histomorphology scores than demineralization with hydrochloric or formic acid, whereas formic acid resulted in higher scores than hydrochloric acid. Demineralization with EDTA yielded DNA amplification in 29 of 36 (81%) samples, whereas demineralization with either acid yielded amplification in only 2 of 72 (3%) samples. Although slightly more time-consuming and labor-intensive, tissue demineralization with EDTA results in superior morphology and is critical for polymerase chain reaction (PCR) amplification with the DNA extraction method described in this article.

Flowcytometric data of intermediate-large cell gastrointestinal lymphoma presenting a gross mass in 32 cats - "let them glow in the flow"

Gastrointestinal lymphoma is the most common form of lymphoma in domestic cats. Aggressive phenotypes are much less common but do bear and unfavorable prognosis. Immunophenotyping by flow cytometry (FCM) is not systematically performed in these patients, because of difficulties in the acquisition of suitable sample material from the gastrointestinal tract. A multimodal diagnostic approach is recommended to improve identification of subtypes targeting patient tailored therapeutic strategies. The aim of this prospective study was to present results of multicolor FCM immunophenotyping in surgically removed gastrointestinal mass and relate them with histopathology using the World Health Organization (WHO) classification and clonality PCR testing. Thirty-two patients were included. Eight cats (25%) had gastric, 23 (72%) had intestinal lymphoma and 1 (3%) had gastric/jejunal lymphoma. Intestinal lymphoma sites were represented by 18 small intestinal, 4 ileocaecal, 1 large intestinal. All gastric lymphomas were diffuse large B-cell lymphoma (DLBCL). Small intestinal lymphomas were 10 enteropathy associated T-cell lymphoma type I (EATL I), 2 enteropathy associated T-cell lymphoma type II (EATL II), 2 peripheral T-cell lymphoma (PTCL), 3 DLBCL and one DLBCL+EATL II. The most common small intestinal FCM T-cell phenotype was CD3+CD21- CD4-CD8-CD18+ CD5-CD79- in 7/10 EATL I and one EATL II. The most frequent FCM B-cell phenotype was CD3-CD21+ CD4-CD8-CD18+ CD5-CD79+ in 13/17 DLBCL and the DLBCL+EATL II. Clonality PCR results were positive in 87.5% (28/32) of all cases. No cross-lineage rearrangement was observed. IHC and FCM results agreed in 87.5% (28/32) of all cases. When all 3 methods were combined, consistent results were seen in 75% (24/32). This is the first demonstration of a multicolor FCM approach set in context to the gold standard histopathology and clonality testing results.

Comparative analysis of primer sets for the assessment of clonality in feline lymphomas

Introduction

Lymphomas are among the most important and common malignant tumors in cats. Differentiating lymphomas from reactive lymphoid proliferations can be challenging, so additional tools such as clonality assessment by PCR are important in diagnosis finding. Several PCR assays have been developed to assess clonality in feline lymphomas. For T-cell lymphomas TRG (T-cell receptor gamma) genes are the preferred target whereas for B-cell lymphomas most primer sets target immunoglobulin heavy chain (IGH) genes. Here we compare commonly used diagnostic primer sets for the assessment of clonality in feline lymphomas under controlled conditions (i.e., identical sample set, PCR setup, amplicon detection system).

Methods

Formalin-fixed and paraffin-embedded samples from 31 feline T-cell lymphomas, 29 B-cell lymphomas, and 11 non-neoplastic controls were analyzed by PCR combined with capillary electrophoresis.

Results and discussion

We show that the combination of the primer sets published by Weiss et al. and Mochizuki et al. provided the best results for T-cell clonality, i.e., correctly assigns most populations as clonal or polyclonal. For B-cell clonality, the combination of the primer sets by Mochizuki et al. and Rout et al. gave the best results when omitting the Kde gene rearrangement due to its low specificity. This study rigorously evaluated various primer sets under uniform experimental conditions to improve accuracy of lymphoma diagnostic and provides a recommendation for achieving the highest diagnostic precision in lymphoma clonality analysis.

Unbiased serum metabolomic analysis in cats with naturally occurring chronic enteropathies before and after medical intervention

Chronic enteropathies (CE) are common disorders in cats and the differentiation between the two main underlying diseases, inflammatory bowel disease (IBD) and low-grade intestinal T-cell lymphoma (LGITL), can be challenging. Characterization of the serum metabolome could provide further information on alterations of disease-associated metabolic pathways and may identify diagnostic or therapeutic targets. Unbiased metabolomics analysis of serum from 28 cats with CE (14 cats with IBD, 14 cats with LGITL) and 14 healthy controls identified 1,007 named metabolites, of which 129 were significantly different in cats with CE compared to healthy controls at baseline. Random Forest analysis revealed a predictive accuracy of 90% for differentiating controls from cats with chronic enteropathy. Metabolic pathways found to be significantly altered included phospholipids, amino acids, thiamine, and tryptophan metabolism. Several metabolites were found to be significantly different between cats with IBD versus LGITL, including several sphingolipids, phosphatidylcholine 40:7, uridine, pinitol, 3,4-dihydroxybenzoic acid, and glucuronic acid. However, random forest analysis revealed a poor group predictive accuracy of 60% for the differentiation of IBD from LGITL. Of 129 compounds found to be significantly different between healthy cats and cats with CE at baseline, 58 remained different following treatment.

Application of automated machine learning for histological evaluation of feline endoscopic samples

Differentiating intestinal T-cell lymphoma from chronic enteropathy (CE) in endoscopic samples is often challenging. In the present study, automated machine learning systems were developed to distinguish between the two diseases, predict clonality, and detect prognostic factors of intestinal lymphoma in cats. Four models were created for four experimental conditions: experiment 1 to distinguish between intestinal T-cell lymphoma and CE; experiment 2 to distinguish large cell lymphoma, small cell lymphoma, and CE; experiment 3 to distinguish granzyme B+ lymphoma, granzyme B- lymphoma, and CE; and experiment 4 to distinguish between T-cell receptor (TCR) clonal population and TCR polyclonal population. After each experiment, a pathologist reviewed the test images and scored for lymphocytic infiltration, epitheliotropism, and epithelial injury. The models of experiments 1-4 achieved area under the receiver operating characteristic curve scores of 0.943 (precision, 87.59%; recall, 87.59%), 0.962 (precision, 86.30%; recall, 86.30%), 0.904 (precision, 82.86%; recall, 80%), and 0.904 (precision, 81.25%; recall, 81.25%), respectively. The images predicted as intestinal T-cell lymphoma showed significant infiltration of lymphocytes and epitheliotropism than CE. These models can provide evaluation tools to assist pathologists with differentiating between intestinal T-cell lymphoma and CE.

Tumor-like lymphoplasmacytic conjunctivitis in the third eyelid in a dog

This report aims to describe a case of tumor-like lymphoplasmacytic conjunctivitis in a 7-year-old spayed-female Pomeranian. On complete ophthalmic examination, a mass with papillary projections was noted on the bulbar surface of the right third eyelid. Debulking of the mass was performed while preserving as much of the third eyelid as possible. On the histopathological examination, the mass was diagnosed as lymphoplasmacytic conjunctivitis with mild epithelial hyperplasia. Although a slight regrowth of the mass was noted 3 weeks after surgery, intralesional injection of triamcinolone acetonide led to its disappearance. There was no further recurrence after 5 months.

Pattern analysis for the diagnosis of inflammatory skin lesions in domestic animals: An overview

Pattern analysis of inflammatory skin diseases is a technique that offers a systematic approach to the histologic diagnosis of skin diseases. First introduced to human dermatopathology in the 1970s, it was widely adopted by veterinary pathologists for the histologic diagnosis of skin diseases in animals. As the inflammatory pattern reflects, to varying extents, aspects of the underlying disease pathogenesis, its use has contributed to the recognition of novel skin diseases in domestic animals, particularly in dogs and cats. Alternative diagnostic approaches used in human dermatopathology, such as "tissue-reaction pattern" and a purely "anatomic approach" have not been as widely used in veterinary pathology. However, veterinary pathologists often combine pattern analysis with anatomic and etiologic factors. This overview outlines the technique, introduces the patterns, and discusses advantages and limitations of pattern analysis in veterinary diagnostic dermatopathology. While molecular analytic techniques and image informatics will undoubtedly prove to be revolutionary in many areas of diagnostic pathology, it is recognized in both human and veterinary arenas that the light microscopic interpretation of hematoxylin and eosin-stained tissue sections will remain the mainstay of routine dermatopathology diagnosis for the foreseeable future.

Prognostic value of increased intraepithelial lymphocytes and lymphocytic clonality in dogs with chronic enteropathy or small-cell lymphoma

The clinical significance of severe infiltration of small intraepithelial lymphocytes (IEL) and the results of polymerase chain reaction for antigen receptor rearrangement (PARR) in dogs with chronic enteropathy (CE) and small-cell lymphoma (SCL) are controversial. This cohort study aimed to evaluate the prognostic significance of the IEL and PARR results in dogs with CE or SCL. Although definitive diagnostic histopathological criteria for SCL in dogs have yet to be established, dogs with the histopathological findings of severe IEL infiltration were diagnosed with SCL in this study. One hundred and nineteen dogs were recruited, with 23 dogs classified as having SCL and 96 dogs as having CE. The positive rate of PARR was 59.6 % (71/119) in the duodenum and 57.7 % (64/111) in the ileum. Subsequently, three dogs with SCL and four dogs with CE developed large-cell lymphoma (LCL). The median overall survival (OS) of dogs with SCL was 700 days (range, 6-1410 days), and that of dogs with CE was not reached. In the log-rank test, shorter OS was observed in cases with histopathological SCL (P = 0.035), clonal TCRγ rearrangement in the duodenum (P = 0.012), and clonal IgH rearrangement in the ileum (P < 0.0001). The Cox proportional hazards model adjusted for sex and age showed that histopathological SCL (hazard ratio [HR] 1.74; 95 % confidence interval [CI], 0.83-3.65), duodenal clonal TCRγ rearrangement (HR, 1.80; 95 % CI, 0.86-3.75), and ileal clonal IgH rearrangement (HR, 2.28; 95 % CI, 0.92-5.70) could shorten overall survival, although their 95 % CIs included 1.0. These results indicate that severe IEL infiltration could be a useful histopathological feature for diagnosing SCL, and clonality-positive results could be a negative prognostic factor in dogs with CE. Furthermore, the development of LCL should be carefully monitored in dogs with CE and SCL..

ACVIM consensus statement guidelines on diagnosing and distinguishing low-grade neoplastic from inflammatory lymphocytic chronic enteropathies in cats

BACKGROUND

Lymphoplasmacytic enteritis (LPE) and low-grade intestinal T cell lymphoma (LGITL) are common diseases in older cats, but their diagnosis and differentiation remain challenging.

OBJECTIVES

To summarize the current literature on etiopathogenesis and diagnosis of LPE and LGITL in cats and provide guidance on the differentiation between LPE and LGITL in cats. To provide statements established using evidence-based approaches or where such evidence is lacking, statements based on consensus of experts in the field.

ANIMALS

None.

METHODS

A panel of 6 experts in the field (2 internists, 1 radiologist, 1 anatomic pathologist, 1 clonality expert, 1 oncologist) with the support of a human medical immunologist, was formed to assess and summarize evidence in the peer-reviewed literature and complement it with consensus recommendations.

RESULTS

Despite increasing interest on the topic for clinicians and pathologists, few prospective studies were available, and interpretation of the pertinent literature often was challenging because of the heterogeneity of the cases. Most recommendations by the panel were supported by a moderate or low level of evidence. Several understudied areas were identified, including cellular markers using immunohistochemistry, genomics, and transcriptomic studies.

CONCLUSIONS AND CLINICAL IMPORTANCE

To date, no single diagnostic criterion or known biomarker reliably differentiates inflammatory lesions from neoplastic lymphoproliferations in the intestinal tract of cats and a diagnosis currently is established by integrating all available clinical and diagnostic data. Histopathology remains the mainstay to better differentiate LPE from LGITL in cats with chronic enteropathy.

Association of globulin concentrations with prognosis in horses with lymphoma

Introduction

Lymphoma is the most common hemopoietic neoplasia in horses. Common clinicopathologic abnormalities in equine lymphoma include hyperglobulinemia, hypoalbuminemia, hyperfibrinogenemia, anemia, thrombocytopenia and lymphocytosis. Hypoglobulinemia has been reported in other species with lymphoma, however it has not been well-described in horses. The objectives of this study were to examine the prevalence of hypoglobulinemia in equine lymphoma, and to identify prognosis and clinicopathological abnormalities associated with serum globulin concentrations.

Methods

Ninety-six horses with lymphoma were investigated in this retrospective study. Patients were allocated into groups based on serum globulin concentration. Survival analysis was performed to determine risk factors associated with globulin concentration and outcome.

Results

Nineteen horses were hypoglobulinemic (≤2.1 g/dL), 63/98 were normoglobulinemic (2.2-4.3 g/dL), and 16/98 were hyperglobulinemic (≥4.4 g/dL). Hyperglobulinemia was associated with a higher anion gap (P = 0.0005), lower bicarbonate (P = 0.006), sodium (P = 0.03) and chloride concentrations (P = 0.002), and higher total protein than hypoglobulinemic horses (P < 0.0001). For location, 37% of horses with mucocutaneous lymphoma were hypoglobulinemic, compared to none in the hyperglobulinemic group (P = 0.02). Survival times were significantly different between low, normal and high globulin groups (P = 0.0002, median [range] survival times: 333 [1-3792], 43 [1-4,001] and 4 [1-129] days, respectively). Significant risk factors for shortened time to death were hyperglobulinemia (HR 2.4, P = 0.02), T cell lymphoma (HR 3.5, P < 0.0001), and multicentric (HR 3.1, P = 0.0008) and mediastinal (HR 6.4, P = 0.006) forms of lymphoma. Lack of chemotherapy was associated with shortened survival time (HR 4.5, P < 0.0001). B cell lymphomas (P < 0.0001) and mucocutaneous lymphoma location (P < 0.0001) were associated with longer survival times.

Discussion

Serum globulin concentrations are associated with location of lymphoma, clinicopathologic abnormalities, and survival times in equine lymphoma.

A clonality assay in canine B cell tumors targeting the immunoglobulin light chain lambda locus

Clonality assays for antigen receptor rearrangement have been used as adjunct examinations of lymphoproliferative diseases. These assays have been useful for differentiation between inflammation and clonal expansion of lymphocytes. Whereas the immunoglobulin heavy chain (IGH) and immunoglobulin light chain kappa (IGK) loci have been targeted in canine clonality assays previously, the immunoglobulin light chain lambda gene (IGL) locus has not yet been investigated. This study aimed to evaluate the usefulness of clonality assays in dogs using IGL. Canine diffuse large B cell lymphomas (DLBCL), cutaneous plasmacytomas, and pathologically diagnosed lymph nodes without lymphoma, were used in this study. Genomic DNA was extracted from formalin-fixed paraffin embedded sections. Sequences of IGLV and IGLJ were obtained from the ImMunoGeneTics database. Several primers against IGLVs and IGLJs were designed in the regions showing homology, by alignment of the gene segments. Products of polymerase chain reaction were analyzed on a capillary electrophoresis. In total, 20 of 23 cases of DLBCL showed clonality (87.0 %), whereas 8 of 30 cutaneous plasmacytomas were clonal (26.7 %). One of 23 lymph nodes without lymphoma showed clonality, thus the specificity was 95.7 %. These data indicate that the IGL locus could be a target for canine clonality assays and that the sensitivity of IGL-based clonality assays in cutaneous plasmacytomas was lower than that in DLBCL.

Pathological Findings in Gastrointestinal Neoplasms and Polyps in 860 Cats and a Pilot Study on miRNA Analyses

Background: Gastrointestinal masses in cats are of clinical relevance, but pathological studies with larger case numbers are lacking. Biomarkers such as miRNA have not yet been investigated in feline intestinal neoplasms. Methods: A retrospective analysis of pathology reports included 860 feline gastrointestinal masses. Immunohistochemistry was performed on 91 lymphomas, 10 sarcomas and 7 mast cell tumours (MCT). Analyses of miRNA-20b and miRNA-192 were performed on 11 lymphomas, 5 carcinomas and 5 control tissues by ddPCR. Results: The pathological diagnosis identified 679 lymphomas, 122 carcinomas, 28 sarcomas, 23 polyps, 7 MCT and 1 leiomyoma. Carcinomas and polyps were most commonly found in the large intestine, lymphomas were most commonly found in the stomach and small intestine and MCT only occurred in the small intestine. Besides the well-described small-cell, mitotic count <2 T-cell lymphomas and the large-cell B-cell lymphomas with a high mitotic count, several variants of lymphomas were identified. The values of miRNA-20b were found to be up-regulated in samples of all types of cancer, whereas miRNA-192 was only up-regulated in carcinomas and B-cell lymphomas. Conclusions: The histopathological and immunohistochemical (sub-)classification of feline intestinal masses confirmed the occurrence of different tumour types, with lymphoma being the most frequent neoplasm. Novel biomarkers such as miRNA-20b and miRNA-192 might have diagnostic potential in feline intestinal neoplasms and should be further investigated.

A clonality analysis based on T-cell receptor beta and delta loci for high-grade gastrointestinal lymphoma in dogs

Clonality assays based on antigen receptors are used as adjunct examinations in the diagnosis of lymphoproliferative diseases. We investigated the usefulness of the T-cell receptor beta (TRB) and T-cell receptor delta (TRD) loci in clonality assays for high-grade gastrointestinal (GI) lymphoma in dogs. For TRB, we used primers reported previously; for TRD, we designed primers for each of the V and J genes based on genomic sequences. Genomic DNA was extracted from 39 formalin-fixed, paraffin-embedded sections of high-grade GI lymphoma diagnosed histologically. The sensitivity of TRB and TRD primers for GI lymphoma was 41.0% and 38.5%, respectively, which was lower than the 82.1% sensitivity of T-cell receptor gamma (TRG) primers However, some cases that could not be detected using TRG primers had clonality with either TRB or TRD primers. We found the TRG locus to be more suitable as a first choice for the assay of canine lymphoma clonality than the TRB and TRD loci. However, the detection rate of T-cell clonality may be enhanced using TRB and TRD primers for lymphoma cases not detected using TRG primers.

Evaluation of clonality from multiple anatomic sites in canine epitheliotropic T cell lymphoma

BACKGROUND

Canine epitheliotropic cutaneous T-cell lymphoma (eCTCL) is thought to represent a disease homologue to human mycosis fungoides (MF). In human MF, neoplastic cells are phenotypically consistent with resident effector memory T cells, a population that remains for an extended period within tissue without circulating. Dogs with eCTCL often present with lesions in multiple locations, raising the question of whether the neoplasm is of the same T-cell subpopulation or not.

OBJECTIVES

To characterize the antigen receptor gene rearrangements of lymphocytes from skin and blood of dogs with eCTCL to determine if neoplastic clones are identical.

ANIMALS

Fourteen dogs with eCTCL.

MATERIALS AND METHODS

Histological and immunohistochemical examination, and PCR for antigen receptor rearrangement (PARR) for T-cell receptor gamma (TRG) performed on multiple cutaneous biopsy samples and blood.

RESULTS

All skin biopsies contained cluster of differentiation (CD)3-positive neoplastic lymphocytes. Within individual dogs, all skin biopsies revealed identical TRG clonality profiles, suggesting that the same neoplastic clone was present in all sites. In the blood, a matching clone was found in six of 14 dogs, a unique clone was observed in nine of 14 dogs, and no clone was detected in two of 14 dogs.

CONCLUSIONS

These findings show that canine eCTCL lesions in multiple locations harbour the same neoplastic clone, neoplastic lymphocytes do not remain fixed to the skin and instead can circulate via blood, differing clones can be identified in skin versus blood, and circulating neoplastic cells can be detected without lymphocytosis.

Cutaneous epitheliotropic T-cell lymphoma in a donkey - a case report

Background

Cutaneous epitheliotropic T-cell lymphoma is a malignant tumour of the skin already reported in humans, dogs, cats, horses, and other species, but not previously in donkeys. The standard diagnosis is based on clinical, morphological and immunophenotypic data. Differentiation of malignant versus benign proliferation of lymphocytes is crucial; in ambiguous cases T-cell receptor gamma (TRG) molecular clonality should be tested. In the present paper, we report a case of mycosis fungoides diagnosed in a donkey whose diagnosis was based on clinical, histological and immunohistochemical aspects and a positive TRG clonality test.

Case presentation

A twenty-five-year-old donkey gelding was referred with a mildly pruritic, generalised and severe exfoliative dermatosis. Otherwise, the animal was clinically healthy, though mildly underweight. Dermatological examination revealed severe generalised alopecic and exfoliative dermatitis, occasionally eroded, with high number of large, thin, greyish scales. All mucocutaneous junctions except the hoofs were affected. Ectoparasites and dermatophytes were ruled out. The complete blood count and blood smear evaluation revealed mild normocytic normochromic anemia. The biochemistry panel showed mild hyperproteinemia with albumin within the normal range. Protein electrophoresis showed moderate polyclonal hypergammaglobulinemia. Histological findings were characterised by interface dermatitis with massive exocytosis in the epidermis of a homogenous population of lymphoid cells showing atypia. Clusters of neoplastic cells were present within the epidermis forming Pautrier “microabscesses”. These findings are consistent with cutaneous epitheliotropic lymphoma. Immunohistochemical staining revealed uniform labelling of the neoplastic cells for CD3, and lack of expression of CD20 (a B cell lineage associated marker). Molecular clonality PCR (PARR) was performed using equine TRG primers; this revealed a clonal rearrangement in a heavy polyclonal background. Transmission electronic microscopy showed multiple lymphocytes with convoluted or cerebriform nuclei.

Conclusions

This case report provides the first evidence of clinical, histopathological, immunophenotypic features, electron microscopy findings and molecular analysis of a cutaneous epitheliotropic T-cell lymphoma (mycosis fungoides) in a donkey. Our observations suggest that cutaneous T-cell lymphoma should be included in the differential diagnoses of exfoliative dermatitis, even those progressing in a chronic pattern and/or with few or no pruritus.

Composition of lymphocyte subpopulations in normal and mildly reactive peripheral lymph nodes in cats

OBJECTIVES

Flow cytometric (FCM) immunophenotyping of lymphoid tissue aspirates is an available adjunct for feline lymphoma diagnostics. Reference data have only been established for feline peripheral blood. Studies investigating the composition of normal and mildly reactive feline lymph nodes (LNs) are lacking. The aim of this prospective study was to establish reference data for lymphocyte subpopulations in normal and mildly reactive feline peripheral LNs using a standardised multicolour panel of antibodies.

METHODS

Macroscopically inconspicuous mandibular and/or popliteal LNs from 31 adult cats, which were euthanased for reasons other than haematological diseases, were excised and processed within 5 h after death. Multicolour flow cytometry using eight different feline-specific, anti-canine and human cross-reactive monoclonal antibodies used in current diagnostic marker panels was performed after cytological exclusion of pathological states and complemented by lymphocyte clonality testing, histopathology and immunohistochemistry (IHC) to ensure the absence of lymphoid disease.

RESULTS

Of 31 cats, the immunophenotyping data of 24 individuals could be included as histopathology and clonality testing excluded a pathological condition. Lymphocyte populations showed the following positive antibody reactions: CD18+ 86.3% ± 13.86%, CD3+ 54.81% ± 11.10%, CD5+ 57.39% ± 12.66%, CD21+ 40.42% ± 12.40%, CD79alphacy+ (CD79αcy) 30.41% ± 13.49% and CD14+ 0.75% ± 1.35%. There were 30.88% ± 13.48% CD4+ and 12.91% ± 6.68% CD8+ cells. Cytology revealed a mixed population of mostly lymphoid cells in all samples. The absence of a monoclonal/oligoclonal neoplastic population was confirmed by lymphocyte clonality testing. Histopathology and IHC showed a normal or mildly reactive pattern in all cases.

CONCLUSIONS AND RELEVANCE

This study establishes FCM immunophenotyping data of lymphocyte populations of normal and mildly reactive feline peripheral LNs. For the first time, anti-CD5, CD4, CD8 and CD21 reference data in normal and mildly reactive feline peripheral LNs are presented. CD18, CD3, CD14 and CD79αcy have been used to establish reference data for the first time in any feline material.

Feline and Canine Cutaneous Lymphocytosis: Reactive Process or Indolent Neoplastic Disease?

Cutaneous lymphocytosis (CL) is an uncommon and controversial lymphoproliferative disorder described in dogs and cats. CL is generally characterized by a heterogeneous clinical presentation and histological features that may overlap with epitheliotropic lymphoma. Therefore, its neoplastic or reactive nature is still debated. Here, we describe clinicopathological, immunohistochemical, and clonality features of a retrospective case series of 19 cats and 10 dogs with lesions histologically compatible with CL. In both species, alopecia, erythema, and scales were the most frequent clinical signs. Histologically, a dermal infiltrate of small to medium-sized lymphocytes, occasionally extending to the subcutis, was always identified. Conversely, when present, epitheliotropism was generally mild. In cats, the infiltrate was consistently CD3+; in dogs, a mixture of CD3+ and CD20+ lymphocytes was observed only in 4 cases. The infiltrate was polyclonal in all cats, while BCR and TCR clonal rearrangements were identified in dogs. Overall, cats had a long-term survival (median overall survival = 1080 days) regardless of the treatment received, while dogs showed a shorter and variable clinical course, with no evident associations with clinicopathological features. In conclusion, our results support a reactive nature of the disease in cats, associated with prolonged survival; despite a similar histological picture, canine CL is associated with a more heterogeneous lymphocytic infiltrate, clonality results, and response to treatment, implying a more challenging discrimination between CL and CEL in this species. A complete diagnostic workup and detailed follow-up information on a higher number of cases is warrant for dogs.

Novel clonality assays for T cell lymphoma in cats targeting the T cell receptor beta, T cell receptor delta, and T cell receptor gamma loci

BACKGROUND

T cell clonality assays in veterinary medicine currently target only the T cell receptor gamma (TRG) locus. Existing assays have suboptimal sensitivity because of insufficient primer coverage of all possible rearrangements.

OBJECTIVE

Develop higher sensitivity clonality assays targeting the TRG, delta (TRD), and beta (TRB) loci in cats.

ANIMALS

Cats with histopathologically confirmed lymphoma (n = 89), non-lymphoma (n = 35), and possible hepatic small cell lymphoma (n = 31).

METHODS

Molecular clonality assay development utilizing our recently reported topology and expressed repertoire data of the T cell receptor loci in cats. Determination of clonality status of lymphoma, non lymphoma, and possible hepatic small cell lymphoma samples, and calculation of assay sensitivity and specificity.

RESULTS

The new multiplex TRG assay yielded the highest sensitivity (95.5%). All assays yielded 100% specificity except for the new multiplex TRG assay (97.3%). The combination of the new TRG and TRB assays yielded sensitivity of 98.9% and specificity of 97.0%. The new TRG assay detected clonality in 17/31 possible small cell lymphoma livers, whereas an existing TRG assay detected clonality in 6/31 livers.

CONCLUSIONS AND CLINICAL IMPORTANCE

The assessment of multiple T cell loci compensates for the potential shortcomings of individual assays. Using a combination of molecular clonality assays will increase the overall sensitivity for the diagnosis of T-cell lymphoma in cats, especially intestinal, and hepatic small cell lymphoma. Hepatic small cell lymphomas detected by the new TRG assay utilized rarely expressed V and J genes not recognized by previous assays, likely indicating unique biology of hepatic small cell lymphoma in cats.

Histopathologic, phenotypic, and molecular criteria to discriminate low-grade intestinal T-cell lymphoma in cats from lymphoplasmacytic enteritis

BACKGROUND

Differentiation of low-grade intestinal T-cell lymphoma (LGITL) from lymphoplasmacytic enteritis (LPE) in cats is a diagnostic challenge for pathologists.

OBJECTIVE

Characterize histologic, immunohistochemical, and molecular features of LGITL and LPE.

ANIMALS

Forty-four client-owned cats, 22 diagnosed with LGITL and 22 with LPE.

METHODS

Prospective, cohort study. Clinical suspicion of LGITL or LPE was based on persistent gastrointestinal signs, unresponsive to empirical treatments. All cats underwent a standardized diagnostic evaluation, including biopsy (preferentially full-thickness), and were diagnosed with LGITL or LPE after review of clinical, laboratory, sonographic, histologic, immunohistochemical, and clonality results.

RESULTS

A monomorphic lymphocytic population (22/22, 100%) and in-depth mucosal infiltration (15/22, 68%) were hallmarks of LGITL. Epithelial patterns (nests and plaques) were significantly more frequent in LGITL (11/22, 50%) than in LPE (1/22, 5%) cases (P = .001). A CD3+ lymphocytic apical-to-basal gradient was observed in 9/22 (41%) of LGITL vs 1/22 (5%) of LPE cases (P = .004). Most LPE cases (17/18, 94%) featured marked fibrosis in the superficial part of the lamina propria. The Ki-67 20%- and 30%-thresholds discriminated between LGITL and LPE within both the epithelium (specificity >95%) and lamina propria (specificity >95%), respectively. All LGITL cases were CD3+ pSTAT3- and pSTAT5+. T-cell receptor gamma chain gene rearrangements indicated monoclonality in 86% of LGITL cases. Surprisingly, 70% of LPE cases featured monoclonality (40%) or monoclonality on a polyclonal background (30%).

CONCLUSIONS AND CLINICAL IMPORTANCE

We identified new histologic, immunohistochemical, and clonality criteria to distinguish LGITL from LPE.

Revisiting lymphocyte clonality testing in feline B-cell lymphoma

Differentiation between resident mature lymphocyte populations and small-cell lymphoma cannot be made by cytological review alone and remains challenging in histopathological review. These cases warrant application of complementary tools like PCR-based immunoglobulin (IG) and T-cell receptor (TCR) clonality testing for confirmation. Although primer coverage of potential IG gene rearrangements in feline B-cell neoplasms constantly improves, the possibility of false negative and false positive test results still poses a problem. In this retrospective study, we assessed diagnostic sensitivity and specificity of a novel developed multiplex PCR assay for routine diagnosis of B-cell clonality. Therefore, 24 feline patients were subjected to comparative clonality testing by using different primer sets. Feline lymphoma cell lines and confirmed patient material served as positive control. Compared to previous studies, this novel developed multiplex PCR assay showed positive effects on diagnostic sensitivity, specificity, accuracy, and positive predictive value accompanied by a slight impairment of negative predictive value. Notably, none of the primer sets was superior; hence, we recommend the combined application of the herein tested primer sets in routine diagnostics. However, a more in-depth-evaluation of the dynamic of assay specific parameters in dependency on primer set usage requires prospective studies on larger cohorts of feline patients.

Evaluation of Prognostic Factors, including Duodenal P-Glycoprotein Expression, in Canine Chronic Enteropathy

The aim of this retrospective single-center study was to evaluate which factors, including expression of P-glycoprotein (P-gp), a membrane-bound protein involved in multiple drug resistance, could predict the response to treatment in canine immunosuppressant-responsive enteropathy (IRE). Dogs with IRE or non-responsive enteropathy (NRE) that were examined from 2005 to 2014 were included and were divided into two groups (IRE vs. NRE). Signalment, history, and clinical and laboratory findings were collected. P-glycoprotein immunohistochemistry was carried out on duodenal biopsies of both groups stored in our biobank, and immunophenotyping and molecular clonality were performed on the NRE samples. Ninety-two dogs were enrolled, 73 IRE (79.3%) and 19 NRE (20.7%), with a prevalence of pure breed (78.3% vs. 21.7%) and male dogs (p < 0.001). Factors associated with a worse prognosis were previous treatment with steroids (p = 0.033) and lower serum total protein concentration (p = 0.005). Clonality testing on the NRE duodenal biopsies showed 5/16 clonal responses, assuming a latent undiagnosed lymphoma as a possible cause of the NRE.

Flow Cytometric Assessment of Ki-67 Expression in Lymphocytes From Physiologic Lymph Nodes, Lymphoma Cell Populations and Remnant Normal Cell Populations From Lymphomatous Lymph Nodes

Recent literature suggests conventional flow cytometric (FCM) immunophenotyping complemented by Ki-67 FCM assessment as a reliable tool to classify canine lymphomas. Ki-67 expression assessed by FCM is rarely reported in canine lymphoma cases and reference data for normal canine lymph nodes are missing. Moreover, nothing is known about the Ki-67 expression within the occasionally observed remnant cell population within the gates of normal lymphocytes in lymphoma cases. Aim of this study was to compare flow cytometric Ki-67 expression of lymphocyte populations from normal canine lymph nodes, lymphoma cells from World-Health-Organisation (WHO) classified lymphoma patient samples and their neighboring normal remnant cell population. Cryopreserved lymphocyte cell suspensions from normal lymph nodes from eight dogs free of lymphoma served as reference material. Fourteen cases diagnosed by cytology, FCM, clonality testing, histopathology including immunohistochemistry consisting of 10 DLBCL, 1 MZL, 1 PTCL and 2 TZL showed a residual small lymphocyte population and were investigated. The Ki-67 expression in normal canine lymphoid tissue was 3.19 ± 2.17%. Mean Ki-67 expression in the malignant cell populations was 41 ± 24.36%. Ki-67 positivity was 12.34 ± 10.68% in the residual physiologic lymphocyte population, which otherwise exhibited a physiologic immunophenotype pattern. This ratio was equivalent (n = 3) or lower (n = 11) than the Ki-67 expression of the malignant cell population within the sample. This is the first report of FCM derived Ki-67 expression combined with immunophenotype patterns in normal canine lymph nodes, compared with lymphoma cell populations and residual normal cell populations of lymphoma cases diagnosed by state of the art technology.

Pathology of growth anomalies in massive Caribbean corals of the family Faviidae

Growth anomalies (GAs) are a morphologically diverse and poorly understood group of lesions affecting corals. The aim of this study was to describe the prevalence and morphology of GAs affecting the faviid corals Diploria labyrinthiformis, Pseudodiploria strigosa, Psudodiploria clivosa, and Colpophyillia natans on St. Kitts. Three gross morphological variants of GAs (exophytic, nodular, and ruminate) were equally prevalent, together affecting 7.8% of corals surveyed across 5 reefs. Prevalence varied by reef and coral species, being highest in C. natans (35.7%). Median colony diameter was larger in corals with GAs relative to those without (Mann-Whitney U test, P < .001). Histopathological examination of exophytic GAs consistently showed corallite and polyp gigantism (n = 7), characterized by polyp enlargement and retained microanatomical structures. In contrast, nodular GAs (n = 9) were consistently hyperplasia of the basal body wall with skeletal dystrophy, composed of micronodular skeletal deposits with abundant hyaline lamellae, bordered by calicoblastic epithelial hyperplasia, interspersed with distorted gastrovascular canals and islands of mesoglea. Endolithic organisms, particularly fungi and algae, were common among GA and apparently healthy biopsies. While pathogenesis of these lesions remains uncertain, a neoplastic basis for GAs on Caribbean faviids could not be established using diagnostic criteria conventionally applied to tumors of vertebrate taxa, in line with other recent observations of coral GAs.

Untargeted metabolomic analysis in cats with naturally occurring inflammatory bowel disease and alimentary small cell lymphoma

Feline chronic enteropathy (CE) is a common gastrointestinal disorder in cats and mainly comprises inflammatory bowel disease (IBD) and small cell lymphoma (SCL). Differentiation between IBD and SCL can be diagnostically challenging. We characterized the fecal metabolome of 14 healthy cats and 22 cats with naturally occurring CE (11 cats with IBD and 11 cats with SCL). Principal component analysis and heat map analysis showed distinct clustering between cats with CE and healthy controls. Random forest classification revealed good group prediction for healthy cats and cats with CE, with an overall out-of-bag error rate of 16.7%. Univariate analysis indicated that levels of 84 compounds in cats with CE differed from those in healthy cats. Polyunsaturated fatty acids held discriminatory power in differentiating IBD from SCL. Metabolomic profiles of cats with CE resembled those in people with CE with significant alterations of metabolites related to tryptophan, arachidonic acid, and glutathione pathways.

Unusual splenic B-cell lymphoma in two related Sumatran tigers (Panthera tigris sumatrae)

CASE DESCRIPTION

A 14-year-old 120-kg (264-lb) sexually intact male Sumatran tiger (Panthera tigris sumatrae) and its 10-year-old 130-kg (286-lb) sexually intact male offspring were housed separately and evaluated independently after experiencing weeks of ongoing malaise, weight loss, and anorexia.

CLINICAL FINDINGS

Both animals were immobilized and anesthetized for physical examinations and diagnostic testing. Complete blood counts revealed leukopenia and anemia in both tigers. Splenomegaly was identified on abdominal ultrasonography. Cytologic examination and immunohistochemical staining of splenic samples confirmed intermediate to large B-cell lymphoma; no evidence of lymphoma in surrounding organs was noted.

TREATMENT AND OUTCOME

The sire was treated with lomustine and prednisolone. This tiger was euthanized 21 months after initiation of treatment because of chronic progressive renal disease. The male offspring was treated with l-asparaginase but did not respond to the treatment. A splenectomy was performed, and malaise and anorexia resolved. No further chemotherapy was administered, and the male offspring was instead maintained on a low dose of prednisolone. Thirty-two months after diagnosis, the male offspring was still considered to be in remission.

CLINICAL RELEVANCE

To our knowledge, this was the first known report of the diagnosis and management of a splenic B-cell lymphoma in a tiger. Both tigers achieved positive clinical responses and long-term survival by means of different treatment modalities. The finding of such an unusual neoplasm in a male tiger and its male offspring was noteworthy, raising the possibility of a genetic predisposition for this lymphoma type.

Use of immune repertoire sequencing to resolve discordant microscopic and immunochemical findings in a case of T cell-rich large B cell lymphoma in a young dog

Background

Lymphocytic neoplasms with frequent reactive lymphocytes are uncommonly reported in dogs, and can pose a diagnostic challenge. Different diagnostic modalities such as cytology, flow cytometry, histopathology, immunohistochemistry, and clonality testing, are sometimes required for a diagnosis. This report illustrates the value of using a multi-modal diagnostic approach to decipher a complex lymphocytic tumor, and introduces immune repertoire sequencing as a diagnostic adjunct.

Case presentation

A 10-month-old Great Dane was referred for marked ascites. Cytologic analysis of abdominal fluid and hepatic aspirates revealed a mixed lymphocyte population including numerous large lymphocytes, yielding a diagnosis of lymphoma. Flow cytometrically, abdominal fluid lymphocytes were highly positive for CD4, CD5, CD18, CD45, and MHC II, consistent with T cell lymphoma. Due to a rapidly deteriorating clinical condition, the dog was euthanized. Post mortem histologic evaluation showed effacement of the liver by aggregates of B cells surrounded by T cells, suggestive of hepatic T cell-rich large B cell lymphoma. Immune repertoire sequencing confirmed the presence of clonal B cells in the liver but not the abdominal fluid, whereas reactive T cells with shared, polyclonal immune repertoires were found in both locations.

Conclusions

T cell-rich large B cell lymphoma is a rare neoplasm in dogs that may be challenging to diagnose and classify due to mixed lymphocyte populations. In this case, the results of histopathology, immunohistochemistry and immune repertoire sequencing were most consistent with a hepatic B cell neoplasm and reactive T cells exfoliating into the abdominal fluid. Immune repertoire sequencing was helpful in delineating neoplastic from reactive lymphocytes and characterizing repertoire overlap in both compartments. The potential pitfalls of equating atypical cytomorphology and monotypic marker expression in neoplasia are highlighted.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-02783-3.

Transcriptional Differences between Canine Cutaneous Epitheliotropic Lymphoma and Immune-Mediated Dermatoses

Canine cutaneous epitheliotropic T-cell lymphoma (CETL) and immune-mediated T-cell predominant dermatoses (IMD) share several clinical and histopathological features, but differ substantially in prognosis. The discrimination of ambiguous cases may be challenging, as diagnostic tests are limited and may prove equivocal. This study aimed to investigate transcriptional differences between CETL and IMD, as a basis for further research on discriminating diagnostic biomarkers. We performed 100bp single-end sequencing on RNA extracted from formalin-fixed and paraffin-embedded skin biopsies from dogs with CETL and IMD, respectively. DESeq2 was used for principal component analysis (PCA) and differential gene expression analysis. Genes with significantly different expression were analyzed for enriched pathways using two different tools. The expression of selected genes and their proteins was validated by RT-qPCR and immunohistochemistry. PCA demonstrated the distinct gene expression profiles of CETL and IMD. In total, 503 genes were upregulated, while 4986 were downregulated in CETL compared to IMD. RT-qPCR confirmed the sequencing results for 5/6 selected genes tested, while the protein expression detected by immunohistochemistry was not entirely consistent. Our study revealed transcriptional differences between canine CETL and IMD, with similarities to human cutaneous lymphoma. Differentially expressed genes are potential discriminatory markers, but require further validation on larger sample collections.

Feline and canine Merkel cell carcinoma: A case series and discussion on cellular origin

Merkel cell carcinoma (MCC) is in humans and cats a malignant cutaneous neuroendocrine carcinoma, whereas in dogs it possibly has a more benign behaviour. It may be cytologically confused with round cell tumours such as lymphoma because of its striking cytomorphologic similarity. Although MCC is considered to arise from Merkel cells, recent findings indicated that primitive (epi‐)dermal stem cells, early B‐cells or dermal fibroblasts were the origin of human MCC. The aim of our study was to evaluate a possible lymphoid origin in feline and canine MCCs. Specific analysis of CD3, PAX‐5, KIT and PARR assay were performed in 3 feline and 3 canine MCCs. All MCCs (6/6) were negative for CD3 and PAX‐5. KIT was expressed in all MCCs (6/6). Assessment of clonality by PARR assay exhibited a polyclonal B‐ and T‐cell receptor rearrangement in all five cases tested. In conclusion, a lymphoid origin of feline and canine MCCs could not be demonstrated. This is in contrast with human MCCs, that often express early B‐cell lineage markers.

Comprehensive comparison of upper and lower endoscopic small intestinal biopsy in cats with chronic enteropathy

Background

Integrating immunohistochemistry (IHC) and clonality testing with histopathology may improve the ability to differentiate inflammatory bowel disease (IBD) and alimentary small cell lymphoma (LSA) in cats.

Hypothesis/Objectives

To evaluate the utility of histopathology, IHC, and clonality testing to differentiate between IBD and LSA and agreement of diagnostic results for endoscopic biopsy (EB) samples from the upper (USI) and lower small intestine (LSI).

Animals

Fifty‐seven cats with IBD or LSA.

Methods

All cases were categorized as definitive IBD (DefIBD), possible LSA (PossLSA), probable LSA (ProbLSA), or definitive LSA (DefLSA) based on histopathology alone. Results from IHC and clonality testing were integrated.

Results

Based on histopathology alone, 24/57 (42.1%), 15/57 (26.3%), and 18/57 (31.6%) cats were diagnosed with DefIBD, PossLSA or ProbLSA, and DefLSA, respectively. After integrating IHC and clonality testing, 11/24 cases (45.8%) and 15/15 cases (100%) previously categorized as DefIBD and PossLSA or ProbLSA, respectively, were reclassified as LSA. A final diagnosis of IBD and LSA was reported in 13/57 (22.8%) and 44/57 (77.2%) cats, respectively. Agreement between USI and LSI samples was moderate based on histopathology alone (κ = 0.66) and after integrating IHC and clonality testing (κ = 0.70). However, only 1/44 (2.3%) of the LSA cases was diagnosed based on LSI biopsy alone.

Conclusions and Clinical Importance

Integrating IHC and clonality testing increased the number of cases diagnosed with LSA, but the consequence for patient outcome is unclear. There was moderate agreement between USI and LSI samples. Samples from the LSI rarely changed the diagnosis.

Retrospective assessment of the clinical relevance of surgical biopsies of abdominal lymph nodes in cats: 51 cases (2014-2018)

OBJECTIVES

The aims of this study were to assess surgical biopsy of abdominal lymph nodes (LNs) in cats taken at the time of exploratory laparotomy and to evaluate any additional benefit of histopathology compared with LN cytology.

METHODS

We carried out a retrospective study from a single institution of cats that had abdominal ultrasound and LN biopsies as part of an exploratory laparotomy (2014-2018). Clinical records were reviewed for presenting signs, medical investigations, ultrasound, cytology, surgical findings and histopathology.

RESULTS

Fifty-one cats were included. In total, 60 LNs were biopsied. Forty-four cats had evident LN enlargement at the time of surgery. Nine of those cases were reported to have normal-sized LNs on ultrasound, including one cat that was subsequently diagnosed with lymphoma. Ultrasound-guided LN aspiration was performed in 19 cases. Five of these cats had a histological diagnosis of neoplasia following biopsy, but only one was correctly identified with cytology. Histopathology results were reactive hyperplasia (n = 41), tumour metastasis (n = 11), lymphadenitis (n = 6), inconclusive (n = 1) and normal (n = 1). The most common final diagnoses were inflammatory bowel disease (n = 17/51) and gastrointestinal lymphoma (n = 10/51). There were 15 cats with neoplastic disease; LN biopsies confirmed metastatic disease in 10 and ruled out nodal involvement in five.

CONCLUSIONS AND RELEVANCE

Surgical biopsy of grossly enlarged or normal abdominal LNs provides additional information to LN cytology in cats and in the majority of cases is associated with a positive histological diagnosis. There appears to be the potential to underdiagnose neoplasia with cytology alone.

First-time application of a PCR-based clonality assay in a large cohort of non-domestic felines

Feline lymphoma, one of the most important malignant tumors in domestic cats, is also increasingly diagnosed in non-domestic felines, most notably, African lions (Panthera leo). The gold standard for the diagnosis of lymphoma is histopathological evaluation. As an additional tool, the PCR for antigen receptor gene rearrangement (PARR) has been established. To support the diagnosis on a molecular level, the PCR-based clonality assay is designed to distinguish between reactive and neoplastic lymphocyte populations. In general, PARR primers are used to target complete immunoglobulin heavy chain V-D-J (IGH-VDJ) and T-cell receptor gamma V-J (TRG-VJ) chain gene rearrangements. In this study, we validated the primer sets used in routine diagnostics of domestic cats for the application in non-domestic felines. Clonality testing was used in 41 non-domestic feline species and the results were interpreted in the light of their clinical history and their pathology. In total, clonality could be detected in 8 non-domestic felines (19.4%), including 3 lymphoma cases confirmed by histopathology. These results confirmed the successful application of domestic feline-specific PARR primers in non-domestic feline species. Diagnostic sensitivity and specificity of the clonality assay were 100% and 88%, respectively. Finally, the overall diagnostic accuracy was 89%.

Canine lymphoma and vector-borne diseases: Molecular and serological evaluation of a possible complicity

Lymphoma is the most common haematological malignancy in dogs and its aetiology is largely unknown. The presence of canine vector-borne agents (CVBD) in lymphoma tissues has been described and its causative effects questioned. We intended to evaluate the presence and extent of Leishmania infantum, Ehrlichia canis, Anaplasma phagocytophilum and Bartonella henselae infection in dogs with lymphoma. Sixty-one dogs, living in the Lisbon metropolitan area, with a diagnosis of lymphoma were enrolled. Immunofluorescence assays were used to detect serum IgG's. The presence of DNA from CVBD agents in tumour tissue was assessed by PCR. All dogs tested negative for B. henselae, A. phagocytophilum and E. canis by both serology and PCR. Regarding L. infantum, 8.2% (n = 5) of the dogs had a positive serologic result. L. infantum DNA was detected in two samples of diffuse large B-cell lymphoma (DLBCL). These results show an increased, but not significant, seropositivity (8.2% vs 7.9%) and molecular detection (3.3% vs 1.2%) for L. infantum in dogs with lymphoma, when compared to the reported canine population in the same geographical area. We could not identify an association between lymphoma and E. canis, A. phagocytophilum, B. henselae or Leishmania infantum infection in the studied population. Nevertheless, further studies, following dogs trough their CVBD disease evolution, are worthwhile and may help clarify a possible role of CVBD agents in lymphomagenesis.

Flow Cytometric Analysis of Mediastinal Masses in Cats: A Retrospective Study

Mediastinal masses occur in dogs and cats and are often investigated with cytology. However, discrimination between the two most common lesions (thymoma and lymphoma) may be challenging, especially when small/medium lymphocytes represent the prevalent population. The aim of the present study is to describe the flow cytometric aspects of mediastinal masses in cats and to assess the ability of flow cytometry (FC) to differentiate lymphoma from non-lymphomatous lesions. We retrospectively describe FC features of fine needle aspiration cytology from cats with mediastinal masses. Cases were grouped in lymphoma and non-lymphoma based on results of cytology, histopathology, PCR for antigen receptor rearrangement (PARR), clinical presentation, and follow-up. Scatter properties, positivities to CD5, CD4, CD8, CD21, CD18, and their co-expressions were recorded using a multicolour approach. Twenty cats were included, 12 lymphomas and eight non-lymphomatous cases. Forward scatter (FSC) of lymphoid cells was higher in the lymphoma group. Double positive CD4+CD8+ T-cells were the dominant population in eight out of 12 lymphomas, whereas non-lymphomatous lesions showed no dominant lymphoid population in five out of eight cases. Unlike dogs, the high prevalence of CD4+CD8+ lymphomas in cats it makes difficult to differentiate lymphoma from non-lymphomatous lesions using FC alone. FC may add interesting information to refine diagnosis in some cases, but PARR and histopathology remain mandatory to solve differential in case of expansion of small–medium sized double positive lymphoid cells.

Differentiation of lymphocytic-plasmacytic enteropathy and small cell lymphoma in cats using histology-guided mass spectrometry

BACKGROUND

Differentiation of lymphocytic-plasmacytic enteropathy (LPE) from small cell lymphoma (SCL) in cats can be challenging.

HYPOTHESIS/OBJECTIVE

Histology-guided mass spectrometry (HGMS) is a suitable method for the differentiation of LPE from SCL in cats.

ANIMALS

Forty-one cats with LPE and 52 cats with SCL.

METHODS

This is a retrospective clinicopathologic study. Duodenal tissue samples of 17 cats with LPE and 22 cats with SCL were subjected to HGMS, and the acquired data were used to develop a linear discriminate analysis (LDA) machine learning algorithm. The algorithm was subsequently validated using a separate set of 24 cats with LPE and 30 cats with SCL. Cases were classified as LPE or SCL based on a consensus by an expert panel consisting of 5-7 board-certified veterinary specialists. Histopathology, immunohistochemistry, and clonality testing were available for all cats. The panel consensus classification served as a reference for the calculation of test performance parameters.

RESULTS

Relative sensitivity, specificity, and accuracy of HGMS were 86.7% (95% confidence interval [CI]: 74.5%-98.8%), 91.7% (95% CI: 80.6%-100%), and 88.9% (95% CI: 80.5%-97.3%), respectively. Comparatively, the clonality testing had a sensitivity, specificity, and accuracy of 85.7% (95% CI: 72.8%-98.7%), 33.3% (95% CI: 14.5%-52.2%), and 61.5% (95% CI: 48.3%-74.8%) relative to the panel decision.

CONCLUSIONS AND CLINICAL IMPORTANCE

Histology-guided mass spectrometry was a reliable technique for the differentiation of LPE from SCL in duodenal formalin-fixed paraffin-embedded samples of cats and might have advantages over tests currently considered state of the art.

The Genetic and Molecular Basis for Canine Models of Human Leukemia and Lymphoma

Emerging details of the gene expression and mutational features of canine lymphoma and leukemia demonstrate areas of similarities and differences between disease subsets in the humans and dogs. Many features of canine diffuse large B-cell lymphoma resemble the ABC form of human DLBCL, including constitutive activation of the NF-kB pathway, and almost universal presence of double expressing MYC/BCL2 lymphomas. Frequent TRAF3 mutations and absence of BCL6 expression are differences with the human disease that need further exploration. Canine peripheral T-cell lymphoma is more common in dogs than in people and behaves in a similarly aggressive manner. Common features of canine and human PTCL include activation of the PI3 kinase pathways, loss of PTEN, and the tumor suppressor CDKN2. There is insufficient data available yet to determine if canine PTCL exhibits the GATA3-TBX21 dichotomy seen in people. Common to all forms of canine lymphoproliferative disease are breed-specific predilections for subsets of disease. This is particularly striking in PTCL, with the Boxer breed being dramatically overrepresented. Breed-specific diseases provide an opportunity for uncovering genetic and environmental risk factors that can aid early diagnosis and prevention.

Clonality testing in the lymph nodes from dogs with lymphadenomegaly due to Leishmania infantum infection

INTRODUCTION

In southern European countries, multicentric lymphoma and leishmaniosis are the main differential diagnoses in dogs presented with generalized lymphadenomegaly. The cytological examination is in some cases inconclusive and polymerase chain reaction (PCR) for antigen receptor rearrangement (PARR) has become a common method to confirm or rule out a lymphoproliferative neoplasia. According to the literature, leishmaniosis may lead to clonal arrangements and therefore to a false diagnosis of lymphoma, but this assumption is made from a single leishmania infected dog. Therefore, the objective of this study was to prospectively evaluate results from PARR in dogs with lymphadenomegaly due to clinical leishmaniosis at the moment of diagnosis.

MATERIALS AND METHODS

31 dogs with a diagnosis of leishmaniosis based on the LeishVet guidelines were included in the study. Samples from enlarged lymph nodes were taken for cytological examination, clonality testing and Leishmania infantum PCR.

RESULTS

All 31 dogs had medium to high positive antibody titers against Leishmania spp. and 30/31 had a positive Leishmania PCR from the lymph node. A polyclonal arrangement for B cells (immunoglobulin heavy chain gene) and T cells (T-cell receptor gamma chain gene) antigen receptors was found in 28/31 dogs. Two out of 31 dogs showed a monoclonal arrangement for Ig with high (1:2) and low (1:7) polyclonal background respectively; and one of the 31 dogs showed a monoclonal arrangement for T cell receptor with low (1:3) polyclonal background.

CONCLUSION

Infections with Leishmania infantum resulted in clonal rearrangement, and therefore in a possible false diagnosis of lymphoma, in 3 out of 31 dogs (9.7%). Although, PARR is a useful method to differentiate lymphoma from reactive lymphoid hyperplasia in dogs with leishmaniosis, mono-/biclonal results should be interpreted carefully, especially in the presence of any degree of polyclonal background, and together with other clinicopathological findings.

Characterization of the fecal microbiome in cats with inflammatory bowel disease or alimentary small cell lymphoma

Feline chronic enteropathy (CE) is a common gastrointestinal disorder in cats and mainly comprises inflammatory bowel disease (IBD) and small cell lymphoma (SCL). Both IBD and SCL in cats share features with chronic enteropathies such as IBD and monomorphic epitheliotropic intestinal T-cell lymphoma in humans. The aim of this study was to characterize the fecal microbiome of 38 healthy cats and 27 cats with CE (13 cats with IBD and 14 cats with SCL). Alpha diversity indices were significantly decreased in cats with CE (OTU p = 0.003, Shannon Index p = 0.008, Phylogenetic Diversity p = 0.019). ANOSIM showed a significant difference in bacterial communities, albeit with a small effect size (P = 0.023, R = 0.073). Univariate analysis and LEfSE showed a lower abundance of facultative anaerobic taxa of the phyla Firmicutes (families Ruminococcaceae and Turicibacteraceae), Actinobacteria (genus Bifidobacterium) and Bacteroidetes (i.a. Bacteroides plebeius) in cats with CE. The facultative anaerobic taxa Enterobacteriaceae and Streptococcaceae were increased in cats with CE. No significant difference between the microbiome of cats with IBD and those with SCL was found. Cats with CE showed patterns of dysbiosis similar to those in found people with IBD.

Clonal hematopoiesis as a model for premalignant changes during aging

Over the course of the human life span, somatic DNA mutations accumulate in healthy tissues. This process has been most clearly described in blood and bone marrow, esophagus, colon, and skin, but cumulative DNA damage likely affects all tissues of the body. Although most acquired genetic variants have no discernable functional consequences, some randomly occurring somatic mutations confer a relative fitness advantage on a single stem cell and its progeny compared with surrounding cells, which may lead to progressive expansion of a clone (i.e., a genetically identical group of cells). When these mutations occur in a cell with the capacity to self-renew and expand, the mutations persist, and such clonal expansion is a risk factor for further mutation acquisition and clonal evolution. Hematopoietic stem cells are a special case of clonal expansion because both the stem cells and their blood cell progeny circulate in large numbers, and these cells are not subject to some of the anatomical restrictions that characterize other tissues in which somatic mutations conferring a fitness advantage also occur. Therefore, clonally restricted hematopoiesis can have biological and clinical consequences that are distinct from clonal expansions in other tissues. Such consequences include not only clonal progression to overt myeloid neoplasia (or, less commonly, to lymphoid neoplasia) driven by acquisition of secondary mutations in the cells of the expanded clone, but also cardiovascular events and, most likely, other diseases that are influenced by aberrant function of mutant blood cells. A more detailed understanding of how clonal hematopoiesis arises and how clonal selection and expansion occur, as well as development of strategies to avert the clinical consequences associated with clonal hematopoiesis, may both improve public health and yield more general insights into the biology of aging.

Significant advances in veterinary oncology - 60 years on

The first edition of the Journal of Small Animal Practice published in February 1960, contained a paper entitled "Recent Treatments of Malignant Neoplasia" by Dr Larry Owen. Now we have reached the 60th anniversary of JSAP, that article provides a baseline from which to review subsequent advances in veterinary oncology, which now includes worldwide networks that have resulted in veterinary oncology becoming the multidisciplinary speciality that it is today. There certainly have been many advances in understanding of the pathology and epidemiology of animal cancers and in methods of diagnosis and treatment. However, the subject has become so large and diverse that not all aspects can be covered in detail here. It should also be acknowledged that there are still many gaps in knowledge in this field and that, because of a lack of randomised clinical trials, the evidence base for what is often regarded as "standard of care" is weak.

Morphologic and Immunohistochemical Characterization of Spontaneous Lymphoma/Leukemia in NSG Mice

The NOD.Cg-Prkdc^scid Il2rg^tm1Wjl/SzJ strain (NOD scid gamma, NSG) is a severely immunodeficient inbred laboratory mouse used for preclinical studies because it is amenable to engraftment with human cells. Combining scid and Il2rg^null mutations results in severe immunodeficiency by impairing the maturation, survival, and functionality of interleukin 2-dependent immune cells, including T, B, and natural killer lymphocytes. While NSG mice are reportedly resistant to developing spontaneous lymphomas/leukemias, there are reports of hematopoietic cancers developing. In this study, we characterized the immunophenotype of spontaneous lymphoma/leukemia in 12 NSG mice (20 to 38 weeks old). The mice had a combination of grossly enlarged thymus, spleen, or lymph nodes and variable histologic involvement of the bone marrow and other tissues. All 12 lymphomas were diffusely CD3, TDT, and CD4 positive, and 11 of 12 were also positive for CD8, which together was consistent with precursor T-cell lymphoblastic lymphoma/leukemia (pre-T-LBL). A subset of NSG tissues from all mice and neoplastic lymphocytes from 8 of 12 cases had strong immunoreactivity for retroviral p30 core protein, suggesting an association with a viral infection. These data highlight that NSG mice may develop T-cell lymphoma at low frequency, necessitating the recognition of this spontaneously arising disease when interpreting studies.

Composite lymphoma of concurrent T zone lymphoma and large cell B cell lymphoma in a dog

Background

Evolution of indolent to aggressive lymphoma has been described in dogs but is difficult to distinguish from the de novo development of a second, clonally distinct lymphoma. Differentiation of these scenarios can be aided by next generation sequencing (NGS)-based assessment of clonality of lymphocyte antigen receptor genes.

Case presentation

An 8-year-old male intact Mastiff presented with generalized lymphadenomegaly was diagnosed with nodal T zone lymphoma (TZL) based on cytology, histopathology, immunohistochemistry and flow cytometry. Thirteen months later, the dog re-presented with progressive lymphadenomegaly, and based on cytology and flow cytometry, a large B cell lymphoma (LBCL) was diagnosed. Sequencing-based clonality testing confirmed the de novo development of a LBCL and the persistence of a TZL.

Conclusions

The occurrence of two distinct lymphoid neoplasms should be considered if patient features and tumor cytomorphology or immunophenotype differ among sequential samples. Sequencing-based clonality testing may provide conclusive evidence of two concurrent and distinct clonal lymphocyte populations, termed most appropriately “composite lymphoma”.

Lack of Bcl-2 expression in feline follicular lymphomas

Bcl-2, an anti-apoptotic protein, is commonly overexpressed in follicular lymphomas in humans. This is usually the result of a chromosomal translocation that transposes the Bcl-2 gene into the immunoglobulin gene locus. The immunohistochemical assessment of this overexpression can be used as a tool for the differentiation of follicular lymphoma and follicular hyperplasia. In cats, little information about the expression of Bcl-2 in follicular lymphoma exists. We investigated 18 follicular lymphomas histologically and immunohistochemically for the expression of Bcl-2, CD3, CD45R, and feline leukemia virus. Clonality was assessed by PCR for antigen receptor gene rearrangements. Although the histology resembled that of their human counterparts, diffuse expression of Bcl-2 within the follicles of the feline lymphomas, as seen in human cases, was not present. Only single cells within the follicles, comparable to the reactive controls, were positive for Bcl-2 expression. The mean survival time of 4.6 y confirmed the indolent character of the tumor. None of the clinical parameters assessed were statistically significant predictors of survival. Furthermore, a statistically significant difference in survival of animals with or without anti-neoplastic therapy was also not demonstrable.

Improved clonality analysis based on immunoglobulin kappa locus for canine cutaneous plasmacytoma

Sensitivity of clonality analysis based on immunoglobulin heavy chain (IGH) in canine cutaneous plasmacytoma is lower than that in diffuse large B cell lymphoma (DLBCL) because of somatic hypermutation occurring at the IGH locus. Therefore, this study aimed to improve the sensitivity of clonality analysis for canine cutaneous plasmacytoma. To achieve this, clonality analysis based on the immunoglobulin kappa chain (IGK) locus was established. Sensitivity and specificity were examined in genomic DNA extracted from formalin-fixed paraffin-embedded sections of cutaneous plasmacytomas, DLBCLs, and lymph nodes without lymphoma. Forward primers were designed based on the IGKV genes, and reverse primers were designed based on the IGKJ genes and kappa deleting element (Kde). Analysis using IGKV and IGKJ primers demonstrated clonality in 24 of 29 cutaneous plasmacytomas (82.8%), while analysis with primers for IGKV and Kde showed clonality in 16 of 29 cases (55.2%). In DLBCL, the IGKV and IGKJ primer set yielded clonality in 18 of 23 cases (78.3%), and the IGKV and Kde primer set yielded 9 of 23 cases (39.1%). No clonal results were obtained from 23 lymph nodes without lymphoma. Sensitivity of the IGKV and IGKJ primer set was significantly higher than that of the IGH primers reported previously. Thus, clonality analysis based on the IGK locus can be utilized for canine B cell tumors. In conclusion, clonality testing based on IGH and IGK may be beneficial as an adjunct tool for diagnosis of canine B cell tumors including cutaneous plasmacytoma.