Soft tissue sarcomas (STSs) and skeletal muscle both appear high scattering on spectral-domain optical coherence tomography (SD-OCT) imaging, which resulted in instances of misclassification by observers in prior soft tissue sarcoma margin assessment studies. Polarization-sensitive optical coherence tomography (PS-OCT) is an extension of OCT that provides additional information about tissue polarization contrast. In this prospective study we wanted to evaluate whether PS-OCT improves tissue differentiation and diagnostic accuracy compared to spectral-domain OCT (SD-OCT) alone. PS-OCT images from surgical margins of 10 resected STS were compared with histopathology to identify characteristic features of normal and neoplastic tissues. Then, six observers of varying OCT image interpretation experience assessed surgical margins from 30 resected STS using SD-OCT alone and SD-OCT combined with PS-OCT. PS-OCT images demonstrated distinct birefringence (optical patterns), corresponding to tissue organization: skeletal muscle exhibited alternating high and low birefringence bands, fascia showed variable birefringence and STS had uniformly low birefringence. Overall diagnostic accuracy was high for both modalities [correct classification rate: SD-OCT alone 93.7% (95% confidence interval (CI): 90.1, 96.0) vs. SD-OCT combined with PS-OCT 92.6% (95% = CI: 89.3, 95.4)]; adding PS-OCT did not significantly improve accuracy across all observers (p = 0.82), though expert observers benefited significantly (p = 0.0018). Interobserver and intraobserver agreement ranged from substantial to near perfect. These findings suggest PS-OCT can be interpreted reliably after brief training and may enhance accuracy for experienced users. Further research should explore structured training and real-time applications for comprehensive surgical margin evaluation.

Feline mammary carcinoma (FMC) is an aggressive and highly metastatic cancer that shares molecular and clinical characteristics with human triple-negative breast cancer (TNBC), making it a relevant comparative model for a disease lacking targeted therapies. This study investigated the feasibility and clinical utility of [64]CuCl2 PET/CT imaging in cats with naturally occurring mammary carcinoma. Eight cats (seven tumour-bearing, one healthy control) were administered an intravenous dose of [64]CuCl2 and underwent whole-body PET/CT imaging. Semi-quantitative analysis was performed using standardized uptake values (SUVs), and tumour-to-muscle ratios were calculated to assess lesion conspicuity. Serum ceruloplasmin concentrations were measured as a marker of systemic copper metabolism. All primary masses were [64]Cu-avid and conspicuous, with consistently elevated tumour-to-muscle ratios across tumour-bearing cats, allowing clear differentiation between neoplastic and normal tissue. Imaging provided additional staging information by identifying locally invasive and metastatic disease that was not fully evident on physical examination. Physiologic tracer distribution was characterized by high uptake in the liver and gallbladder and low uptake in skeletal muscle, which served as a reliable reference tissue. Serum ceruloplasmin concentrations varied widely and did not correlate with tumour uptake. These findings suggest that [64]CuCl2 PET/CT is a feasible functional imaging modality for FMC, potentially aiding in tumour detection. This was an exploratory study, and not all imaging results could be confirmed by cytology or histopathology. Nonetheless, our findings suggest that [64]CuCl2 PET/CT should be investigated further as a method for probing copper utilization in FMC.

The infiltrative growth of sarcomas represents a challenge for complete resection, as tumour borders are not easily detectable. Fluorescence guided surgery (FGS) allows improved visualization of tumour margins and could improve resection accuracy. Unfortunately, studies validating the impact of FGS are rare, and direct comparisons of different dyes are not available. Dogs (n = 20) that were presented for sarcoma resection were prospectively enrolled and randomized to either receive indocyanine green (ICG, Group 1) or a targeted anti-αvβ3 integrin probe (Group 2) prior to surgery. FGS was performed in both groups with the surgeon blinded to treatment. The false positive and false negative rates as well as tumour-to-background ratio (TBR) were calculated for each dye. Correlation of fluorescent area and histologically confirmed tumour extension was determined using the Dice Coefficient (DC). The clinical impact of FGS was determined by assessing the rate of rightfully adapted resections. False positive signal was detected in 9/10 dogs in group 1 and 3/10 dogs in group 2. Mean TBR at skin level was higher in group 2 (4.5 and 5.3) compared to group 1, and this difference reached significance in formalin-fixed tissue (5.3 vs. 2.6, p = 0.016). Correlation of fluorescent signal and histologic tumour extent was strong for both dyes (DC group 1 = 0.64; group 2 = 0.78). Resection of additional neoplastic tissue based on FGS was more frequent in group 2 (3/10 dogs) compared to group 1 (1/10 dogs). The initial results of this study indicate that the targeted anti-αvβ3 integrin probe is more tumour selective than ICG in dogs. This pilot as well as the subsequent follow up study are registered at animalstudyregistry.org https://doi.org/10.17590/asr.0000321.

The association between lymphovascular invasion (LVI) and outcomes in dogs with thyroid carcinoma is inadequately described, and a standardized definition of LVI is lacking. This study's objectives were to histopathologically and immunohistochemically characterize LVI and to evaluate associated clinical outcomes in dogs with thyroid carcinoma. Inclusion criteria were: dogs that underwent thyroidectomy for thyroid carcinoma with available histopathology samples, and a minimum of 1-year postoperative follow-up data or follow-up to death. Thirty dogs with 35 distinct tumours, including 26 follicular and nine medullary, were evaluated. LVI was characterized as intracapsular endothelialized tumour emboli (without adhered fibrin) in 26 samples, intracapsular tumour emboli with adhered fibrin in seven samples, extracapsular tumour emboli without adhered fibrin in 10 samples, and extracapsular tumour emboli with endothelial disruptions and adhered fibrin in three samples. CD31 and Prox1 positive vessels contained endothelialized tumour thrombi in 17 and one sample, respectively. Extracapsular invasion with (non-endothelialized) and without (endothelialized) associated fibrin were associated with a 10-fold (p = 0.001) and 3-fold (p = 0.013) increase in the likelihood of death, respectively. No significant difference in the likelihood of death was noted between cases of extracapsular invasion with or without fibrin (p = 0.31). Intracapsular tumour thrombi with or without associated fibrin and non-endothelialized tumour thrombi were not associated with outcomes in this cohort. These results support that in dogs with thyroid carcinoma, extracapsular LVI with or without associated fibrin thrombi, but not intracapsular LVI, is associated with worse outcomes. Further study is warranted on a larger population of dogs with standardized treatment and follow-up.

Carcinomas are the second most common feline intranasal neoplasm. Various treatment options, including radiotherapy, surgery or a combination of both, have been described, but data on medical therapy efficacy are lacking. This retrospective study evaluated the outcome of cats with nasal carcinoma (NC) treated with antineoplastic treatment. Cats with a histopathological or cytopathological diagnosis of NC were included. Patients receiving antineoplastic treatment were compared to patients receiving palliative treatment alone. Response to therapy, median time to progression (MTTP) and median survival time (MST) were described and compared for both groups. Analysed clinical variables included the presence of epistaxis, facial deformity, stage, use of NSAIDs and previous surgical debulking. Thirty-three cats were included in the study: 18 in the antineoplastic treatment group and 15 in the palliative treatment group. Forty-eight percent of the entire population had worsening of the clinical signs, 36% remained stable and 16% showed clinical benefit. MTTP of the entire population was 104 days and MST was 178 days. No statistically significant differences were found between groups for either MTTP (96 vs. 111 days; p = 0.95) or MST (197 vs. 262; p = 0.77). None of the evaluated clinical variables was associated with outcome. In this retrospective study, antineoplastic treatment was not associated with a detectable survival advantage over palliative treatment alone. These findings should be interpreted cautiously given the small sample size and heterogeneity of treatments administered.

Doxorubicin is commonly used in the treatment of canine lymphoma and other malignancies but is associated with adverse effects, including gastrointestinal toxicity and myelotoxicosis. Previous veterinary studies have suggested that prophylactic antimicrobial administration may reduce chemotherapy-associated toxicity and hospitalisation. However, the potential benefits of prophylactic antimicrobials must be balanced against risks, including antimicrobial resistance and dysbiosis. This retrospective study evaluated the effect of prophylactic trimethoprim-sulfadiazine administration on gastrointestinal and haematologic adverse events in dogs with high-grade multicentric lymphoma receiving doxorubicin for the first time. Medical records from three referral hospitals in Queensland, Australia were reviewed for dogs treated between January 2008 and November 2025. Adverse events occurring within 14 days of doxorubicin administration were retrospectively graded using the Veterinary Cooperative Oncology Group Common Terminology Criteria for Adverse Events. Sixty dogs met the inclusion criteria, including 21 dogs receiving prophylactic TMS and 39 receiving no prophylactic antibiotics. Gastrointestinal toxicity occurred in 14/21 (66.7%) dogs receiving TMS compared with 13/39 (33.3%) dogs receiving no antibiotics (p = 0.013). After controlling for lymphoma stage, prophylactic TMS administration was associated with a 3.69-fold increase in the odds of GI toxicity (95% CI 1.13-12.11, p = 0.031). No significant differences were identified between groups in severity of GI toxicity, haematologic toxicity, neutropenia or hospitalisation rates. Prophylactic TMS administration during doxorubicin chemotherapy was associated with increased GI toxicity in this cohort, contrasting with previous reports and supporting the need for prospective evaluation of prophylactic antimicrobial use in contemporary geographically distinct canine chemotherapy populations.

Radiation therapy (RT) has become increasingly available in veterinary medicine and practitioners are likely to encounter RT adverse events (AEs). General knowledge and recognition of AEs associated with RT may be variable among allied specialists; therefore, the aim of this study was to evaluate the perception and awareness of AEs associated with RT within the veterinary specialty groups of ACVIM-(Oncology), ACVECC, and ACVR-(Radiation Oncology). A survey was performed via the respective specialty board e-mail list servs between May 14, 2024 and Aug 30, 2024. A total of 189 complete and 13 partially complete responses were included for statistical analysis. Participants evaluated their clinical perceptions and knowledge of veterinary RT on a 1 to 5 scale with 5 indicating strong agreement. Awareness and perception of veterinary RT among ACVIM-(Oncology) and ACVECC specialists was overall positive. Allied specialists with more than 10 years of clinical experience were more confident in their ability to identify and treat AEs. Despite the reported confidence among allied specialists in identifying AEs and overall favourable perception of RT, 35.7% (10/28) of Veterinary Radiation Oncologists reported having a patient euthanized outside of their care due to, in their opinion, treatable acute AEs associated with RT. Favourable perceptions of RT among allied specialists should be leveraged for targeted continuing education focusing on the identification of commonly encountered RT AEs.

Feline oral squamous cell carcinoma (FOSCC) is the most common oral malignancy, characterised by aggressive local invasion, frequent bone involvement, and poor prognosis. The limited availability of well-characterised in vitro models has hindered the understanding of tumour heterogeneity and invasive behaviour. This study aimed to establish and comparatively characterise a panel of FOSCC cell lines derived from tumours with and without documented bone invasion to identify intrinsic biological differences. Four FOSCC cell lines were evaluated for epithelial identity, growth kinetics, clonogenicity, migratory capacity and chemosensitivity. All cell lines retained epithelial characteristics, with consistent expression of epithelial markers; however, variation in cytokeratin-19 and vimentin suggested phenotypic heterogeneity and partial epithelial-mesenchymal plasticity. The cell lines demonstrated distinct proliferation rates, doubling times, and clonogenic capacities. Morphologically, these cells displayed varying degrees of peripheral filopodial activity. Functional assays further revealed substantial migratory capacity under both serum-supplemented and serum-free conditions, with differences across cell lines. Chemosensitivity profiling showed heterogeneous responses to targeted and cytotoxic agents, highlighting cell line-specific differences in drug susceptibility and potential intrinsic drug responsiveness. These findings demonstrate that FOSCC cell lines possess distinct biological properties consistent with phenotypic differences. The observed heterogeneity underscores the potential relevance of tumour origin in shaping functional behaviour and highlights the value of using multiple, well-characterised cell line models to better represent disease diversity. This study provides a comprehensive comparative characterisation of four FOSCC cell lines, including a newly established model, and establishes a baseline resource for future mechanistic and translational investigations in feline and comparative oncology.

Canine soft tissue sarcomas (STSs) are locally invasive tumours, making local recurrence a major clinical challenge. Time to recurrence (TTR) and associated immune factors remain poorly characterized. This study aimed to characterize the immune microenvironment of canine STS and identify factors associated with TTR. Medical records from 27 dogs with STS that recurred after surgery were reviewed. Histopathological, transcriptomic, and immunological analyses were performed in a tissue-available subcohort of 20 dogs. Immune-related gene expression was characterized using the NanoString canine IO panel. Tumour-infiltrating immune cells and tertiary lymphoid structures (TLSs) were assessed immunohistochemically using CD3, CD20, and FoxP3. Associations with TTR were evaluated using Cox proportional hazards models and log-rank tests. Median TTR was 358 days. Age and tumour location were associated with TTR in univariable analyses of the full cohort, but neither age nor the overall location effect remained significant when analysed together. Higher NOD2 expression and Cluster 1 assignment were associated with shorter TTR across exploratory multivariable models. Cluster 1 tumours exhibited abundant lymphocyte infiltration and enrichment of immunosuppressive pathways, whereas Cluster 2 tumours demonstrated lower immune infiltration and proinflammatory signatures. TLS-positive tumours had greater lymphocyte infiltration, with FoxP3+ cells accumulated within TLSs. Paired recurrent tumours contained significantly more large TLSs than primary tumours. Higher NOD2 expression and an immunologically active but suppressed tumour phenotype were associated with shorter TTR, whereas the association with anatomical location was model-dependent. Regulatory T cells and TLSs may contribute to the immune landscape associated with local recurrence and warrant further investigation as potential therapeutic targets.

Feline mammary carcinomas remain a major therapeutic and prognostic challenge in veterinary oncology because they combine high malignant potential, early dissemination, and substantial heterogeneity in clinicopathologic behaviour. This review summarizes current clinical knowledge on epidemiology, risk factors, diagnostic work-up, staging, treatment, and prognostic assessment of feline mammary carcinomas, highlighting areas of consensus and persistent controversies. Progress in care will require prospective, multicentre studies built on harmonized staging and pathology reporting, enabling risk-adapted treatment pathways that are both evidence-based and clinically actionable.

Canine cancer imposes substantial emotional, financial and decisional burden on owners navigating complex referral pathways and treatment options. Understanding how owners experience and interpret these pathways is essential to improving care delivery. We conducted a retrospective social media listening study using Pulsar Platform to retrieve public Anglophone posts relating to canine cancer across multiple platforms. After cleaning, de-duplication and zero-shot large language model relevance filtering (accuracy 88%-99%, F1 93%-98%, with precision up to 99% on Reddit), 11 878 posts were analyzed (of those that could be geolocated, most originated from the USA). Sentiment and emotion classification, thematic extraction and non-negative matrix factorization topic modelling were applied. Pre-specified subsets examined cost-focused (n = 2008), referral-focused (n = 341) and steroid-focused (n = 438) discourse. Overall, negative sentiment predominated (66%), with sadness the most frequent emotion (64%). Across platforms, quality of life (QoL) functioned as the primary decision-making framework, operationalized through appetite, mobility, comfort, engagement and "good days". Referral narratives highlighted delays, diagnostic sequencing uncertainty, travel burden and perceived gatekeeping within referral pathways. Financial constraint frequently shaped treatment feasibility, influencing decisions regarding chemotherapy, surgery, steroid-only palliation and euthanasia. Steroids were often described as a palliative bridge or cost-constrained alternative when advanced oncology care was inaccessible. General practise (GP) veterinarians were consistently referenced as trusted information anchors, influencing referral uptake and treatment trajectories. Topic modelling suggests a cancer-care pathway experienced as structurally constrained despite strong owner willingness to pursue treatment. QoL consistently supersedes cure as the dominant evaluative metric. Earlier cost transparency, clearer shared-care communication and strengthened GP-oncologist coordination may reduce decisional distress and help mitigate avoidable barriers to specialist care.

Gilvetmab is a caninised monoclonal antibody against canine PD-1. Concurrent or sequential administration of anti-PD-1 antibodies and radiation therapy (RT) improves survival time in various species. Eighteen dogs with mast cell tumours (MCTs) were prospectively treated with 24 Gy of RT over Days 0, 7 and 21 and gilvetmab every 2 weeks beginning on the second fraction of RT (Day 7) for up to 10 doses. Best tumour response was complete in one (6%), partial in eight (44%) and stable disease in nine dogs (50%) for an ORR of 50%. Median time to best response was 7 days after the first fraction of RT. Thirteen dogs (72%) developed progressive disease with a median progression free interval (PFI) of 116 days after the first fraction of RT. Nine adverse events (AEs) attributed to gilvetmab were recorded in seven dogs (39%) consisting of infusion reactions in four, metabolic changes in three and gastrointestinal signs and pancreatitis in one each. Overall, five dogs (28%) experienced Grade 3 AEs. Radiation AEs were limited to Grade 1 for both acute and late effects in seven dogs (39%). There was a significant difference in PFI and MST for dogs with and without lymph node metastasis with a median PFI of 64 versus 292 days and MST of 103 versus 587 days (p = 0.02 and 0.005, respectively). This sequence, or combination, of therapies did not provide durable tumour control for canine MCT and the AE profile warrants further evaluation.