Canine cutaneous mast cell tumours (MCTs) demonstrate variable clinical behaviour. Histological grading remains the primary prognostic approach, but some low-grade tumours behave aggressively, and interobserver variability persists. This underscores the need for complementary and objective biomarkers. Raman spectroscopy (RS) is a non-destructive optical technique based on the inelastic scattering of monochromatic light capable of detecting subtle biochemical changes in tissues. This exploratory study evaluates whether RS could differentiate low-grade from high-grade cutaneous MCTs based on characteristic vibrational signatures. Eighteen canine cutaneous mast cell tumours were graded according to the Kiupel two-tier system, comprising 10 low-grade and 8 high-grade cases. Formalin-fixed tumour samples were analysed, yielding a total of 68 Raman spectra. Spectra were acquired with a 785 nm laser, pre-processed using baseline correction, and normalized to the 1007 cm-1 phenylalanine band. Data normality was tested with the Shapiro-Wilk test, and group comparisons used the Mann-Whitney U test (α = 0.05). The 1007 cm-1 band showed no significant difference between Low- and High-Grade tumours (p = 0.068), validating its use for normalization. Conversely, the 860 cm-1 tyrosine-associated band was significantly higher in high-grade tumours (p = 0.033). Ratios normalized to the 1007 cm-1 peak consistently discriminated between grades, with significantly higher values in low-grade tumours across multiple spectral regions-particularly 1007/1299 and 1007/1301-1320 (all p < 0.05). Overall, RS identified distinct biochemical fingerprints between tumour grades in canine cutaneous MCTs, especially in spectral regions associated with amino acids, lipids, and nucleic acids. These findings support the potential of RS as a complementary tool for MCT characterization and encourage further validation in larger cohorts with clinical outcome data.

Methylation analysis of LINE-1 elements in canine cutaneous mast cell tumors.

Abstract Background The Golden Retriever Lifetime Study (GRLS) is a prospective cohort of dogs within the contiguous United States, designed to investigate health of Golden Retrievers, with cancer as a research focus. Mast cell tumour (MCT) represents the most common skin malignancy in dogs. This is the first exploration of MCT epidemiology within the GRLS cohort, and the first epidemiologic report specific to MCT in the Golden Retriever breed. Methods MCT frequency was reported as proportion of the cohort, and incidence rate for first lifetime diagnosis. A lifetable was produced to assess incidence risk per year of age. The anatomical location, tissue origin and histopathologic grade of MCTs themselves were reported descriptively. Dogs with multiple MCT presentations or metastasis were further explored. Survival was compared between dogs with MCT and the remaining cohort, followed by a stratified analysis of time from first MCT diagnosis to death using Kaplan-Meier curves and the log-rank test. Results Within the cohort of 3,044 dogs, 164 (5.39%) dogs were diagnosed with 234 MCTs, corresponding to an incidence rate of 5.58 per 1,000 dog years at risk (95% confidence interval (95% CI): 4.76–6.51). Median overall lifespan was 11.68 years (95% CI: 11.25–12.33) in dogs diagnosed with MCT and 11.75 years (95% CI: 11.61–11.98) within the remaining cohort - with no statistically significant difference observed (log-rank test, p = 0.54). Regarding histologic grade, 47 of 234 tumours (20.09%) met the GRLS high-grade definition (with either Kiupel high or Patnaik grade 3 characteristics). De novo tumours were diagnosed in 26 dogs (15.85%), local recurrence occurred in 8 dogs (4.88%) and metastasis in 16 dogs (9.76%). Median survival time from first MCT diagnosis was 1,367 days (95% CI: 1200–1870) with only 11.59% ( n = 19) having MCT recorded as cause of death. After stratification, survival was statistically significantly decreased in MCT cases where there was presence of local recurrence, presence of metastasis, or high histopathological grade (log-rank test, p &lt; 0.05). Conclusions This epidemiological study reports age-specific frequency, clinical features and prognostic factors for Golden Retrievers with MCT. In this cohort, the lifespan of dogs with MCT diagnosis was not statistically significantly different from the remaining cohort.

BackgroundImmune checkpoint inhibitors (ICIs) have transformed oncology in human medicine, providing clinical benefit in a broad spectrum of cancers. Widely available ICIs for dogs are lacking.Hypothesis/ObjectivesEvaluate efficacy and safety of gilvetmab, a caninized anti-PD-1 monoclonal antibody.AnimalsFifty-one client-owned dogs were evaluated, 25 with stages II-III melanoma and 26 with stages I-III mast cell tumor (MCT). Fifteen dogs with stages III-V lymphoma were also evaluated.MethodsMulti-institutional, open-label study. Enrolled dogs were treated with gilvetmab IV at 6 mg/kg q28d or 10 mg/kg q14d; 8 dogs receiving the lower dosage underwent dose escalation with their owners’ consent. Safety was evaluated by physical examinations, laboratory testing, and clinical observations made by veterinarians or the dogs’ owners. Efficacy was assessed by objective response rate (ORR) and time to progression (TTP) using cRECIST v1.0 and lymphoma response criteria.ResultsFor melanoma, the ORR was 20% (95% confidence interval [CI], 7%-41%) and median TTP was 56 days. For MCT, the ORR was 46% (95% CI, 27%-67%) and median TTP was not reached. No objective responses were observed in dogs with lymphoma. Serious adverse events of anaphylaxis, hypotension, or tumor hemorrhage occurred in 3 dogs (3/51, 5.9%). Tumor enlargement before regression, consistent with possible pseudoprogression, was observed in 2 dogs with melanoma.Conclusions and clinical importanceGilvetmab has a reasonable expectation of efficacy and an acceptable preliminary safety profile in dogs with MCT stages I-III and melanoma stages II and III.

Electrochemotherapy (ECT) is a local ablative treatment and in veterinary oncology, evidence supporting ECT efficacy is mainly derived from case reports and small case series, underscoring the need for standardized, multicentric data collection comparable to human oncology registries. The primary aim of this study was to establish VetInspECT, a veterinary clinical registry adapted from the human InspECT platform, to enable standardized reporting and multicentre data collection for ECT. The secondary aim was to evaluate antitumor effectiveness using data from the single centre that initiated the registry. VetInspECT was designed to systematically record patient characteristics, tumor features, treatment parameters, and follow-up outcomes in animals treated with ECT. Retrospective data spanning from 2012 to 2024 from feline patients treated at a Slovenian center were entered into the database. Squamous cell carcinoma (SCC) was the most frequently treated tumor (66%), followed by mast cell tumors (MCT; 12%) and other carcinomas and sarcomas. Complete response rates were highest in MCT (95%), followed by non-SCC carcinomas (90%), SCC (74%), and sarcomas (33%). Tumor size, clinical stage, anatomical location, and mucosal involvement significantly affected treatment response and progression-free survival. In conclusion, VetInspECT represents an important step toward standardized ECT reporting in veterinary oncology and supports the use of shared registries to enable robust multicentric analyses and broader clinical integration of ECT.

Pet dogs with naturally occurring cancers provide valuable models for comparative oncology and pathology tumour registries offer a powerful resource for onco-epidemiological research. Here, we analysed the Small Animal Veterinary Surveillance Network (SAVSNET) pathology-based tumour registry (PTR), one of the largest veterinary tumour registries to date, focusing on four major canine tumours: mast cell tumour (MCT), osteosarcoma (OSA), haemangiosarcoma (HSA), and melanoma (MEL). A case-control study was conducted using a subset of 130 998 histologically confirmed tumours drawn from the pathology tumour registry containing over 1.1 million canine tumour records from 1.02 million dogs collected in the UK between 2010 and 2023. Case-control analyses were performed for melanoma, haemangiosarcoma, OSA and MCT using a denominator population of dogs attending first-opinion veterinary practices. Additionally for MCT, comparisons were made against dogs diagnosed with other tumour types ('tumour denominator' approach). Breed-specific risks were identified, including high odds ratios (OR) for Bulldog-related breeds and Retrievers with mast cell tumours (MCTs) (OR up to 6.8, 95% CI 6.0, 7.6), Rottweilers, Shar Pei and Giant-Schnauzer with melanoma (OR up to 50.3, 95% CI 24.7, 102.5), and German Shepherd Dogs, Mastiffs, and Bullmastiffs with haemangiosarcoma (OR up to 28.0, 95% CI 10.6, 40.9). Higher-grade MCT were diagnosed at older ages and certain breeds were more predisposed to higher-grade MCT (Shar Pei, Rottweiler) while others were more prone to low-grade MCTs (Boxer, Boston Terrier). Neutered dogs generally had higher tumour odds than entire dogs; for example, in MCTs, female-neutered vs. female-entire showed OR 1.81 (95% CI 1.6, 2.0) in ages 3-6, with similar patterns across older age bands. In general, the difference in OR values between entire and neutered dogs was consistently more pronounced in females than in males. These findings demonstrate the value of the SAVSNET PTR as a comprehensive resource for canine tumour surveillance, with potential to support health initiatives and cancer research by identifying breed-specific and demographic risk factors as well as a foundational tool for comparative cancer epidemiology.

PD-L2 reverse signaling suppresses tumor cell proliferation and serves as a prognostic indicator in canine high-grade mast cell tumors.

Prognostic relevance of selected nucleotide variants in canine cutaneous mast cell tumors.

Linking faecal microbiota changes to clinical and prognostic features in dogs with mast cell tumours through 16S rRNA gene sequencing.

Cancer is a leading cause of morbidity and mortality in middle- to old-aged dogs and cats, yet detailed epidemiological data remain limited. This study investigated the distribution of nine major cancer types in dogs and cats using hospital records from the Veterinary Medical Teaching Hospital at the University of California, Davis (2000-2019). Sarcoma, carcinoma, lymphoid neoplasia (LN), mast cell tumor (MCT), and melanoma were analyzed using multivariable logistic regression to assess associations with breed, age, and sex-neuter status. Among 150,063 patients (79.9% dogs; 20.1% cats), 26,883 were diagnosed with cancer (18.1% of dogs; 17.0% of cats). Older age was the strongest predictor of these cancers in both species, though odds of sarcoma, LN, and MCT declined in senior dogs (≥12 years). The following associations were specific to dogs. Spayed females had higher odds of LN (OR=1.43), MCT (OR=1.92), and melanoma (OR=1.63) compared to intact females, whereas neutering had no significant effect in males. Male dogs had higher odds of LN than females, both intact (OR=1.59) and spayed/neutered (OR=1.15), while spayed females had higher odds of MCT than neutered males (OR=1.28). Sarcoma and carcinoma odds varied by age and sex-neuter status, with significant interactions. Aging more strongly affected sarcoma in females regardless of neuter status and carcinoma in intact females and neutered males. Intact females consistently had lower odds of sarcoma but higher odds of carcinoma in old age. These findings highlight complex, cancer-type-specific associations. A California-wide cancer registry would provide a more comprehensive picture of cancer epidemiology in companion animals.

Canine cutaneous mast cell tumour (MCT) is the most common skin neoplasm in dogs, with histopathology serving as both the diagnostic and primary prognostic tool. However, identifying reliable biomarkers is essential for improving clinical decision-making. CD30, a member of the TNF receptor superfamily, is well-characterised in human haematopoietic malignancies. However, its role in canine MCTs remains unclear. This study aimed to evaluate CD30 expression in neoplastic mast cells and tumour-infiltrating lymphocytes (TILs), and to assess its prognostic significance in canine cutaneous MCTs. Immunohistochemical analysis of CD30, CD3, and PAX-5 was performed on 53 samples, and RNA sequencing was conducted to assess CD30 transcript levels in 17 cases. CD30 was detected in 94.6% of neoplastic mast cells, with strong staining observedin 35 cases and weak staining in 18. Strong CD30 expression (p = 0.0051), CD30+ TIL counts (p = 0.0105) andthediffuseinfiltratedistribution pattern of CD3+ TILs (p = 0.0497) were associated with shorter post-surgical survival. RNA sequencing confirmed higher CD30 (TNFRSF8) gene expression levels in high-risk tumours (logFC = 2.3182; FDR = 0.0405). These findings suggest that CD30 is a promising biomarker with potential prognostic value in canine cutaneous MCTs.

Cervical extradural mast cell tumour in a 2-year-old Irish Sport Horse colt.

In 2019, a wild-caught Malayan sun bear (Helarctos malayanus), rescued from the illegal pet trade and relocated to the Edinburgh Zoo (UK), was diagnosed with mast cell tumor (MCT) affecting a hindlimb. Surgical excision was performed at the initial site in the tarsal region, with a repeat excision 2 y later following a relapse, without evidence of metastatic spread. In 2023, MCT metastases were detected in the popliteal lymph node and prostate, prompting a novel treatment approach combining prednisolone and toceranib to alleviate the clinical signs. Four months after initiating treatment, the sun bear was euthanized on welfare grounds. The autopsy and histopathology confirmed the presence of a MCT involving the prostate and the popliteal and iliac lymph nodes. An incidental pheochromocytoma was identified in an adrenal gland. MCT and pheochromocytoma in the Ursidae family, with detailed description of these neoplasms, their microscopic and immunohistochemical features, have not been reported previously, to our knowledge.

Platelets contribute to cancer progression, and thrombocytosis is a recognized poor prognostic factor in human oncology; however, its significance in veterinary medicine remains underexplored. We retrospectively analyzed 166 dogs diagnosed with neoplasia and thrombocytosis (platelet count ≥ 430,000/μL) to assess the relationship between thrombocytosis intensity and survival. Survival analyses revealed that compared with dogs with mild thrombocytosis, those with moderate‐to‐severe thrombocytosis had significantly shorter survival times. With respect to specific diagnoses, dogs with mammary carcinoma and moderate‐to‐severe thrombocytosis had a significantly higher risk of death (HR = 3.4; p = 0.02). A similar trend was observed in patients with mast cell tumors, where the risk of death was 7.39 times higher, although this finding reached only borderline statistical significance (p = 0.05). Further prospective studies with larger cohorts are warranted to validate thrombocytosis as a prognostic biomarker and to elucidate its role in tumor biology and clinical outcomes in veterinary oncology.

Datasets from 849 dogs ≤ 3 years of age were analysed retrospectively, considering breed, sex, anatomic sites, multiplicity, tumour diameter, grading, and immunohistochemistry by using IBM® SPSS Statistics (version 29.0.2.0). Danish-Swedish farm dogs (OR: 8.11, 95% CI 3.33-19.77, p < 0.001) and English Setters (OR: 6.68, 95% CI 3.20-13.97, p < 0.001) showed the highest odds ratios (ORs) compared to crossbreeds. German Shepherd Dogs showed lower ORs (OR: 0.05, 95% CI 0.007-0.364, p < 0.01). The most common sites affected in the young dogs were the trunk (39.2%), hind limbs (24.9%), head (10.1%), fore limbs (7.4%), and pinnae (5%). Patnaik grading revealed 330 grade I (35.7%), 580 grade II (62.8%), and 14 grade III MCTs (1.5%). Kiupel "low grade" was found in 903 MCTs (97%), and 21 MCTs were "high grade" (3%). The prevalence of grade I MCTs was higher in Boxers (48.0%, p < 0.05) and Pugs (67.9%, p < 0.01). Pinnal MCTs were mostly grade I (58.3%, p < 0.01). In 6% (n = 51), multilocalised MCTs were found, and Golden Retrievers (12.5%, p = 0.02) and Pugs (21.4%, p = 0.005) were more affected than crossbreeds. Out of 87 dogs, 20 showed a Ki-67 count above the cut-off as well as KIT staining pattern II. The findings warrant heightened vigilance in evaluating cutaneous lesions in young dogs and highlight similarities and differences compared to the general dog population. Analysis of survival data is required to evaluate how the findings translate into a clinical setting.

This study aimed to evaluate the density, subtypes, and potential functional roles of mast cells in canine transmissible venereal tumors (TVTs) during tumor progression (pretreatment) and regression following vincristine therapy. Biopsy samples were collected from dogs at 3 different time points: day 0 (n = 20), day 7 (n = 20), and day 14 (n = 10). Total mast cell counts were assessed using toluidine blue (TB) staining, while immunohistochemistry for chymase and tryptase was performed to classify mast cell subtypes. Masson's trichrome staining was used to evaluate the severity of fibrosis during regression. In addition, immunohistochemical expression of stem cell factor (SCF) and protease-activated receptor 2 (PAR2) were examined to explore the possible roles of mast cells in the tumor microenvironment. In the late regression group (day 14), the number of TB-, tryptase-, and/or chymase-positive mast cells increased by 3.46, 2.49, and 3.4 times, respectively, compared with the progression group (day 0). In addition, the number of SCF-positive cells and the expression of PAR2 were 6- and 2.38-fold higher in the day 14 group compared with day 0, respectively. While mast cell accumulation is a known feature of various tumors, its precise role in tumor biology remains controversial. The findings of this study suggest a potential role of mast cells and their associated mediators in tumor regression and tissue remodeling processes of TVTs.

Mast cell tumours are the most common skin neoplasms in dogs, accounting for up to 21% of all cutaneous tumours. They typically appear as firm nodules, most often on the trunk, limbs, or head, and their biological behaviour depends on the grade. Diagnosis is based on cytology and histopathology, while surgical excision with adequate margins remains the treatment of choice, often requiring reconstructive techniques in anatomically sensitive areas, such as the eyelid. The article describes two cases of lower eyelid mast cell tumours in dogs, surgically treated using the lip-to-lid technique with lymphadenectomy of the sentinel lymph node. This method allowed complete excision while preserving eyelid function and appearance. Histopathology revealed different tumour grades, resulting in distinct prognoses and postoperative strategies regarding adjuvant chemotherapy. In both cases the final outcome was positive, with no local reoccurrence or distant metastases. The use of lip-to-lid technique can be successfully used for the reconstruction of the lower eyelid defect after mast cell tumour removal. Sentinel lymph node mapping plays an essential role in perioperative staging for these tumours, and provides crucial information about prognosis. Multimodal approach for diagnosis and treatment of mast cell tumours is important to achieve a good long-term outcome. These cases contribute to the limited literature on lower eyelid mast cell tumours and support the integration of advanced staging techniques, including sentinel lymph node mapping, with reconstructive surgery in the management of periocular MCTs.

Mast cell tumors are the most common skin neoplasm in dogs and may be influenced by reproductive status. A gonadectomy modifies gonadotropin levels and may affect the expression of hormonal receptors and proliferative factors; however, the evidence for this remains limited. The objective of this study was to evaluate the expression of VEGF, IGF-1, PCNA, Ki-67, c-KIT, LHR, FSHR, and ERα in intact and neutralized female dogs with and without MCTs. Gene expression in the skin samples was quantified by a real-time PCR, and four groups were included: intact controls (n = 10), neutralized controls (n = 10), intact MCT (n = 9), and neutralized MCT (n = 10). Tumor presence was associated with increased expression of LH and FSH receptors and c-KIT, while angiogenic and proliferative factors (PCNA, Ki-67, IGF-1, VEGF, and ERα) showed lower expression. In dogs with MCTs, a gonadectomy was associated with higher c-KIT and VEGF expression but lower LHR mRNA levels. PCNA expression was lower in the neutralized MCT dogs compared to the neutralized controls, whereas no differences were observed in the intact dogs. Additionally, ERα expression was higher in the neutralized control dogs than in the intact controls, with no differences detected in the MCT dogs. These findings suggest that reproductive status is associated with differential regulation of molecular pathways involved in canine MCT biology.

Gonadectomy is performed in bitches to prevent unwanted reproduction and reduce the risk of sex hormone-related conditions. However, growing evidence suggests that the timing of spaying may influence long-term susceptibility to non-reproductive diseases. This retrospective case–control study (2013–2023) evaluated the association between timing of spaying and the development of orthopedic and neoplastic disorders in a Belgian referral-hospital population. Cases included bitches diagnosed with cranial cruciate ligament rupture, hip dysplasia, elbow dysplasia, lymphoma, mast cell tumor, osteosarcoma, or hemangiosarcoma, while disease-free bitches served as controls. Associations between disease occurrence and spaying status were assessed using multivariable logistic regression adjusted for age, weight category, and body condition score. Age at gonadectomy (<12 vs. ≥12 months) and timing relative to the first estrus were evaluated in separate models. Spaying <12 months of age was associated with increased odds of all conditions compared with intact females. Spaying ≥12 months of age was associated with lower odds of several orthopedic and neoplastic outcomes compared with early spaying, although odds were not always comparable to those in intact females. Large body size and higher body condition score were independently associated with increased odds of orthopedic outcomes. These findings support individualized spaying strategies rather than a universal age threshold.

The use of digitized slides for histopathological diagnosis has become common in veterinary pathology, and the validation of diagnostic techniques that are extrapolated from the evaluation of glass slides is needed. The goal of this study is to evaluate the efficiency of counting mitotic figures in physical glass slides and digitized slides of cutaneous tumors of dogs and cats. The mitotic count was performed by three pathologists on glass and digitized slides of ninety skin tumors, including 30 squamous cell carcinomas in dogs and cats, 30 mast cell tumors and 30 soft tissue tumors in dogs. An additional assessment of cellular proliferation was performed with immunohistochemistry for Ki67. Spearman's correlation for the mean count of mitotic figures between the three observers on physical and digitized slides demonstrated a strong positive correlation for squamous cell carcinomas and mesenchymal tumors and a moderate correlation for mast cell tumors. Inter-observer agreement was moderate between the two methods. In conclusion, the results found suggest that digitized slides can be used reliably for mitotic figure counting in cutaneous neoplasms in small animals, without compromising their classification or prediction of prognosis.