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Background Polymerase chain reaction for antigen receptor rearrangement (PARR) is a molecular diagnostic tool used for discrimination of lymphoid malignancies in dogs from benign processes. Assay variations have been described and are commercially available, but performance metrics are not uniformly reported. Objectives To describe performance (accuracy, sensitivity, specificity) and rigorous benchmarking of a PARR protocol (ePARR) in clinically relevant samples. Animals One hundred eighty‐one client‐owned dogs. Methods Lymphoma and benign tissues representative of the clinical spectrum with gold standard histopathologic and immunohistochemical diagnoses were collected. Assay development and benchmarking were performed on fresh frozen (FF) tissue, formalin‐fixed paraffin‐embedded (FFPE) tissue, flow cytometry pellets, and air‐dried fine‐needle aspirates (FNA). Assay performance was determined for FFPE from 56 dogs (18 B‐cell lymphoma, 24 T‐cell lymphoma, and 14 non‐lymphoma), 80 frozen flow cytometry pellets (66 B‐cell lymphoma, 14 T‐cell lymphoma, 0 non‐lymphoma), and 41 air‐dried FNA slides (23 lymphoma, 18 non‐lymphoma). Results For discrimination of lymphoma versus non‐lymphoma, ePARR had 92% and 92% sensitivity and specificity on FFPE with 92% accuracy, 85% sensitivity from flow cytometry pellets (non‐lymphoma was not evaluated to calculate specificity) with 85% accuracy, and 100% and 100% sensitivity and specificity for FNA with 100% accuracy. Stringent quality control criteria decreased assay success rate without significant performance improvement. Performance metrics were lower in most cases for discrimination of B‐ or T‐cell versus non‐B‐ or non‐T‐cell samples than for lymphoma versus non‐lymphoma. Conclusions and Clinical Importance These benchmarking data facilitate effective interpretation and application of PARR assays in multiple sample types.

Background Regional lymph nodes are frequently sampled in cats with suspected intestinal lymphoma; however, their diagnostic value has not been explored. Objectives To investigate whether histologic and immunohistochemical analysis of mesenteric lymph nodes correlates with the diagnosis of intestinal lymphoma in cats. Animals One hundred 2 client‐owned cats diagnosed with intestinal lymphoma. Methods Retrospective study. The inclusion criteria required a full‐thickness biopsy of the small intestine and concurrent excision of mesenteric lymph nodes. Histologic and immunophenotypic analyses were performed on intestinal biopsies and corresponding lymph nodes. Selected nodal samples diagnosed with reactive lymph nodes underwent clonality testing. Results Transmural T‐cell lymphomas, encompassing small and large cell types, were predominant (64 cases, 62.7%), with large B‐cell lymphomas being more frequently transmural (68.8%) than mucosal (31.2%). Among all lymph nodes examined, 44 (43.1%; 95% CI: 33.9%‐52.8%) exhibited neoplastic infiltration. Among cases of small cell lymphoma, 51 out of 72 (70.8%; 95% CI: 59.4%‐80.1%) showed no nodal involvement. Clonality results correctly identified 19/30 (63.3%; 95% CI: 45.5%‐78.2%) reactive lymph nodes. Concerns were raised regarding clonal identification in the remaining cases and potential misdiagnoses based on phenotypic characteristics. Conclusion and Clinical Importance The study underscores the potential drawbacks of relying solely on mesenteric lymph nodes for diagnosing intestinal lymphomas in cats, particularly small cell subtypes. It emphasizes the importance of full‐thickness biopsies for assessing transmural infiltration and recommends caution when utilizing mesenteric lymph nodes for histologic, immunohistochemical and clonality evaluations in mucosal lymphomas. Despite limitations, this research highlights the need for comprehensive diagnostic strategies in cats with intestinal lymphoma.

We present here the K9 lymphoma assay, a novel 31-gene targeted next-generation sequencing panel designed for genomic profiling of canine lymphoid neoplasms. Addressing the growing demand for advanced diagnostics in veterinary oncology, this assay enables sensitive identification of known and actionable mutations specific to canine lymphomas, while evaluating its prognostic potential to facilitate diagnosis and prognosis. Our analysis, spanning several B- and T-cell lymphoma histotypes, unveiled distinct mutational landscapes distinguishing tumors derived from immature versus mature lymphocytes. Clustering analysis revealed a shared genetic origin between diffuse large B-cell lymphoma and marginal zone lymphoma, aligning with findings in human lymphomas, with TRAF3 emerging as the most frequently mutated gene across B-cell lymphoma subtypes. Significantly, TP53 mutations demonstrated universal adverse prognostic implications across B-cell lymphomas. Additionally, SETD2 mutations contributed to shorter time-to-progression, underscoring the role of epigenetic dysregulation in B-cell tumors. In T-cell lymphomas, SATB1 and FBXW7 were frequently mutated, warranting further investigation in larger cohorts. Our findings advocate for tailored therapeutic approaches based on the genetic profile, impacting treatment decisions and outcomes in canine lymphoma management. This study provides pivotal insights bridging veterinary and human oncology, paving the way for comprehensive genomic diagnostics and therapeutic strategies in comparative oncology.

Background Cytopathology is a minimally invasive and convenient diagnostic procedure, often used as a substitute for histopathology to diagnose and characterize lymphoma in dogs. Objectives Assess the diagnostic performance of cytopathology in diagnosing lymphoma and its histopathological subtypes in dogs. Animals One‐hundred and sixty‐one lymph node samples from 139 dogs with enlarged peripheral lymph nodes. Methods Based only on cytopathology, 6 examiners independently provided the following interpretations on each sample: (a) lymphoma vs nonlymphoma; (b) grade and phenotype; and (c) World Health Organization (WHO) histopathological subtype. Histopathology and immunohistochemistry (IHC) findings were used as reference standards to evaluate diagnostic performance of cytopathology. Clinical, clinicopathologic, and imaging data also were considered in the definitive diagnosis. Results Classification accuracy for lymphoma consistently was >80% for all examiners, whereas it was >60% for low grade T‐cell lymphomas, >30% for high grade B‐cell lymphomas, >20% for high grade T‐cell lymphomas, and <40% for low grade B‐cell lymphomas. Interobserver agreement evaluated by kappa scores was 0.55 and 0.32 for identification of lymphoma cases, and of grade plus immunophenotype, respectively. Conclusions and Clinical Importance Cytopathology may result in accurate diagnosis of lymphoma, but accuracy decreases when further characterization is needed. Cytopathology represents a fundamental aid in identifying lymphoma and can be used as a screening test to predict grade and phenotype. However, these results must be confirmed using other ancillary techniques, including flow cytometry, histopathology, and immunohistochemistry (IHC).

Background Canine breeds may be considered good animal models for the study of genetic predisposition to cancer, as they represent genetic clusters. From epidemiologic and case collection studies it emerges that some breeds are more likely to develop lymphoma or specific subtypes of lymphoma but available data are variable and geographically inconsistent. This study was born in the context of the European Canine Lymphoma Network with the aim of investigating the breed prevalence of canine lymphoma in different European countries and of investigating possible breed risk of lymphoma overall and/or different lymphoma subtypes. Results A total of 1529 canine nodal lymphoma cases and 55,529 control cases from 8 European countries/institutions were retrospectively collected. Odds ratios for lymphoma varied among different countries but Doberman, Rottweiler, boxer and Bernese mountain dogs showed a significant predisposition to lymphoma. In particular, boxers tended to develop T-cell lymphomas (either high- or low-grade) while Rottweilers had a high prevalence of B-cell lymphomas. Labradors were not predisposed to lymphoma overall but tended to develop mainly high-grade T-cell lymphomas. In contrast with previous studies outside of Europe, the European golden retriever population did not show any possible predisposition to lymphoma overall or to specific subtypes such as T-zone lymphoma. Conclusion Further prospective studies with more precise and consistent subtype identification are needed to confirm our retrospective results and to create the basis for the investigation of possible genes involved in different predispositions.

Background High-grade lymphoma in dogs is a chemotherapy-responsive neoplasia with remission rates exceeding 80% under combination chemotherapy protocols. Usually these protocols are intensive and 24 + weeks. The objective of the present study was to investigate if a shorter protocol combined with an oral lomustine maintenance treatment (3 × in 8 weeks) would present an acceptable result, both for B- and T-cell lymphomas, and for the different types of lymphomas normally encountered in private veterinary practice. Results 144 dogs entered the study. Lymphoma types included multicentric (n = 123), alimentary (n = 13), miscellaneous (n = 7), and mediastinal lymphoma (n = 1). Overall response rate was 83.3% (B-cell: 86.6%, T-cell: 79.4%). Complete remission (CR) was achieved in 72.2% (B-cell: 77.3%, T-cell: 67.6%) and partial remission (PR) in 11.1% (B-cell: 9.3%, T-cell: 11.8%) of the dogs. Median duration of first CR amounted to 242 days (B-cell: 263 d, T-cell: 161 d). Median survival in dogs with CR was 374 days (B-cell: 436 d, T-cell: 252 d), and median overall survival time was 291 days (B-cell: 357d, T-cell: 210d). Immunophenotype demonstrated an independent significant influence on duration of remission and survival in the whole group. Findings of splenic and hepatic cytology were not significant associated with patient outcome. Treatment was well tolerated; the majority of adverse events were classified as grade 1 or 2. Conclusions Short-term chemotherapy followed by lomustine consolidation leads to compara-ble remission and survival times compared to conventional protocols with cyclophosphamide, doxorubicin, vincristine and prednisolone with acceptable toxicosis in dogs with both B-cell and T-cell lymphoma.

Background Canine lymphoma represents the most frequent haematopoietic cancer and it shares some similarities with human non-Hodgkin lymphoma. Matrix metalloproteinases (MMPs) and vascular endothelial growth factor (VEGF) play a coordinated role during invasion and proliferation of malignant cells; however, little is known about their role in canine haematologic malignancies. The aim of this study was to investigate the mRNA and protein expression of VEGF and the most relevant MMPs in canine lymphoma. Lymph node aspirates from 26 B-cell and 21 T-cell lymphomas were collected. The protein expression levels of MMP-9, MMP-2 and VEGF-A were evaluated by immunocytochemistry, and the mRNA levels of MMP-2, MMP-9, MT1-MMP, TIMP-1, TIMP-2, RECK, VEGF-A and VEGF-164 were measured using quantitative RT-PCR. Results MT1-MMP, TIMP-1 and RECK mRNA levels were significantly higher in T-cell lymphomas than in B-cell lymphomas. Higher mRNA and protein levels of MMP-9 and VEGF-A were observed in T-cell lymphomas than in B-cell lymphomas and healthy control lymph nodes. A positive correlation was found between MMP-9 and VEGF-A in T-cell lymphomas. Moreover, MMP-9, MT1-MMP, TIMP-1 and VEGF-A were expressed at the highest levels in high-grade T-cell lymphomas. Conclusions This study provides new information on the expression of different MMPs and VEGF in canine lymphoma, suggesting a possible correlation between different MMPs and VEGF, immunophenotype and prognosis.

Background Neoplasm in South American camelids (SAC) are commonly described. The most frequently reported type of neoplasm are lymphomas and difference in the age suffering from lymphomas of and llamas is seen. This report describes a case of a solitary lymphoma in a 5 years and 9 month old llama mare displaying the approach of diagnostic imaging and successful surgical treatment. Case presentation The llama was referred to the clinic for dyspnoea and inspiratory abnormal respiratory sounds. The clinical examination comprised blood cell count, ultrasonographic and radiographic examinations, endoscopy and fine needle aspiration cytology of a mass detected in the mid cervical region. The mass was surgically removed. Histopathological examination of the surgically removed mass diagnosed a malignant T-cell- lymphoma. According to the results of the clinical, ultrasonographic and radiographic examinations no tumor invasion was apparent in distant organs and the llama was discharged from the clinic seven days after surgery. Conclusion Lymphoma has been reported to be the most common neoplasia in camelids and are more often described in young alpacas and in adult llamas. To the author´s knowledge the case presented here is the first that described a broad panel of diagnostic tools including ultrasound, radiographs, endoscopy, fine needle aspiration cytology and histopathoogical examination as well as a successful surgical treatment of a solitary lymphoma in camelids.

Studying lymphoma in canines yields insight into therapies for people — with a bonus of helping the animals. Studying lymphoma in canines yields insight into therapies for people — with a bonus of helping the animals.

A 5‐year‐old spayed female American Staffordshire was referred for weakness, reluctance to move and distension of the abdomen. Three weeks before, the dog underwent surgery for excision of a nodular mass suspected to be a non‐epitheliotropic cutaneous T‐cell lymphoma (NE‐CTCL). Computed tomography revealed heterogeneous enhancing mesenteric masses and nodular lesions of soft tissue density, and infiltration of the abdominal muscular wall. Moreover, a pattern of diffuse muscle nodules in the skeletal muscles was visible, with lesions showing homogenous, heterogeneous or ring enhancement. Necrosis was histologically observed and these lesions were infiltrated by CD3‐positive and CD20‐, CD79a‐ and Iba1‐negative neoplastic lymphocytes. On the basis of the immunopathological features metastatic NE‐CTCL was suspected. Skeletal muscle metastasis has been rarely reported in small animals and this case report further confirms that this possibility should be considered in dogs with lymphoma. Skeletal muscles metastases are considered quite rare in small animals. When it occurs, muscle metastases typically involve paravertebral muscle and hind limb. Whole‐body CT is of paramount importance in patients affected by neoplasms with potential systemic metastases.