Mitotic index is predictive for survival for canine cutaneous mast cell tumors

Masked pre-training of transformers for histology image analysis

In digital pathology, whole-slide images (WSIs) are widely used for applications such as cancer diagnosis and prognosis prediction. Vision transformer (ViT) models have recently emerged as a promising method for encoding large regions of WSIs while preserving spatial relationships among patches. However, due to the large number of model parameters and limited labeled data, applying transformer models to WSIs remains challenging. In this study, we propose a pretext task to train the transformer model in a self-supervised manner. Our model, MaskHIT, uses the transformer output to reconstruct masked patches, measured by contrastive loss. We pre-trained MaskHIT model using over 7000 WSIs from TCGA and extensively evaluated its performance in multiple experiments, covering survival prediction, cancer subtype classification, and grade prediction tasks. Our experiments demonstrate that the pre-training procedure enables context-aware understanding of WSIs, facilitates the learning of representative histological features based on patch positions and visual patterns, and is essential for the ViT model to achieve optimal results on WSI-level tasks. The pre-trained MaskHIT surpasses various multiple instance learning approaches by 3% and 2% on survival prediction and cancer subtype classification tasks, and also outperforms recent state-of-the-art transformer-based methods. Finally, a comparison between the attention maps generated by the MaskHIT model with pathologist's annotations indicates that the model can accurately identify clinically relevant histological structures on the whole slide for each task.

Photo-triggered caffeic acid delivery via psyllium polysaccharide- gellan gum-based injectable bionanogel for epidermoid carcinoma treatment

Here, the simultaneous effect of chemo- and photothermal therapy against epidermoid carcinoma (EC) was investigated. A novel hydrogel, termed bionanogel (BNG), was designed using psyllium mucilage polysaccharide and bacterial gellan gum, incorporated with nanocomplex carrying caffeic acid (CA) and IR-820, and further characterized. The dual effect of BNG and 808 nm laser (BNG + L) on EC was investigated. Staining and scratch assays were performed to analyze their therapeutic effect on EC. In vivo evaluations of BNG + L in xenograft models were performed. Rapid transition, limited swelling, degradability and high tensile strength indicated BNG stability and sustained drug release. Irradiation with 808 nm laser light at 1.25 W /cm2 for 4 min resulted in a temperature increase of 53 °C and facilitated cell ablation. The in vitro studies showed that BNG + L suppressed cancer progression via a late apoptotic effect. The in vivo study showed that the slow release of CA from BNG + L significantly attenuated EC with low mitotic index and downregulation of proteins involved in cancer proliferation such as EGFR, AKT, PI3K, ERK, mTOR and HIF-1α. Thus, BNG could be a novel medium for targeted and controlled drug delivery for the treatment of epidermoid cancer when triggered by NIR light.

Mitotic activity: A systematic literature review of the assessment methodology and prognostic value in canine tumors

One of the most relevant prognostic indices for tumors is cellular proliferation, which is most commonly measured by the mitotic activity in routine tumor sections. The goal of this systematic review was to analyze the methods and prognostic relevance of histologically measuring mitotic activity that have been reported for canine tumors in the literature. A total of 137 articles that correlated the mitotic activity in canine tumors with patient outcome were identified through a systematic (PubMed and Scopus) and nonsystematic (Google Scholar) literature search and eligibility screening process. Mitotic activity methods encompassed the mitotic count (MC, number of mitotic figures per tumor area) in 126 studies, presumably the MC (method not specified) in 6 studies, and the mitotic index (MI, number of mitotic figures per number of tumor cells) in 5 studies. A particularly high risk of bias was identified based on the available details of the MC methods and statistical analyses, which often did not quantify the prognostic discriminative ability of the MC and only reported P values. A significant association of the MC with survival was found in 72 of 109 (66%) studies. However, survival was evaluated by at least 3 studies in only 7 tumor types/groups, of which a prognostic relevance is apparent for mast cell tumors of the skin, cutaneous melanoma, and soft tissue tumor of the skin and subcutis. None of the studies using the MI found a prognostic relevance. This review highlights the need for more studies with standardized methods and appropriate analysis of the discriminative ability to prove the prognostic value of the MC and MI in various tumor types. Future studies are needed to evaluate the influence of the performance of individual pathologists on the appropriateness of prognostic thresholds and investigate methods to improve interobserver reproducibility.

Atypical Mitotic Figures Are Prognostically Meaningful for Canine Cutaneous Mast Cell Tumors

Cell division through mitosis (microscopically visible as mitotic figures, MFs) is a highly regulated process. However, neoplastic cells may exhibit errors in chromosome segregation (microscopically visible as atypical mitotic figures, AMFs) resulting in aberrant chromosome structures. AMFs have been shown to be of prognostic relevance for some neoplasms in humans but not in animals. In this study, the prognostic relevance of AMFs was evaluated for canine cutaneous mast cell tumors (ccMCT). Histological examination was conducted by one pathologist in whole slide images of 96 cases of ccMCT with a known survival time. Tumor-related death occurred in 11/18 high-grade and 2/78 low-grade cases (2011 two-tier system). The area under the curve (AUC) was 0.859 for the AMF count and 0.880 for the AMF to MF ratio with regard to tumor-related mortality. In comparison, the AUC for the mitotic count was 0.885. Based on our data, a prognostically meaningful threshold of ≥3 per 2.37 mm2 for the AMF count (sensitivity: 76.9%, specificity: 98.8%) and >7.5% for the AMF:MF ratio (sensitivity: 76.9%, specificity: 100%) is suggested. While the mitotic count of ≥ 6 resulted in six false positive cases, these could be eliminated when combined with the AMF to MF ratio. In conclusion, the results of this study suggests that AMF enumeration is a prognostically valuable test, particularly due to its high specificity with regard to tumor-related mortality. Additional validation and reproducibility studies are needed to further evaluate AMFs as a prognostic criterion for ccMCT and other tumor types.

Case report: Adjuvant therapy with toceranib for an incompletely resected renal cell carcinoma with suspected pulmonary metastasis in a dog

Primary renal neoplasia is rare in humans and dogs, with renal cell carcinoma (RCC) being the most common form of this cancer. As RCC is often diagnosed at an advanced stage, pulmonary metastasis is frequently observed. Tyrosine kinase inhibitors (TKIs) are the standard adjuvant treatments for metastatic RCC in humans. Similarly, in veterinary medicine, recent trials have employed TKIs for early-stage RCC patients who underwent complete surgical resection and showed no distant metastasis. However, the use of TKIs has not yet been reported commonly in cases of advanced RCC with metastasis. This case study presents the first clinical outcomes of TKI therapy in a dog with incompletely resected RCC and metastasis. A 5-year-old spayed female Chihuahua was referred to our hospital with a right renal mass and multiple pulmonary nodules suspected to be metastases. A portion of the renal mass was surgically removed, and histopathological examination revealed RCC with a high mitotic index. Adjuvant chemotherapy was administered, owing to incomplete resection with suspected pulmonary metastasis. An anticancer drug response prediction test was conducted using patient tissues. Since toceranib showed the most favorable responsiveness, it was selected as a therapeutic agent. Toceranib was orally administered at a dosage of 2.27 mg/kg every 48 h. Regular medical records for potential adverse effects were obtained, including systemic blood pressure, complete blood count, serum biochemical examination, and urinalysis. After 2 weeks of toceranib therapy, partial remission of pulmonary nodules continued for 2 months. The patient did not experience any adverse effects of the anticancer drug during the 4-month follow-up period. However, the patient died from an unidentified cause 6 months after the initial detection of the renal mass. This report describes the use of toceranib in dogs with RCC. In the present case, the patient showed an initial response to chemotherapy, and despite the presence of several poor prognostic factors, the dog survived beyond the expected 3-month lifespan to 6 months. Notably, no adverse events were observed during treatment.

Presence of Gastrointestinal Paraneoplastic Syndrome at Diagnosis in Dogs With Cutaneous Mast Cell Tumors and Its Influence on Disease-Free Interval and Survival

Paraneoplastic syndrome (PNS) is a combination of signs unrelated to the physical presence of a tumor and/or its metastases. Its presence may result in poorer clinical outcomes and prognosis. Gastrointestinal ulceration is a well-known PNS in animals with cutaneous MCT. This retrospective study analyzed the occurrence of gastrointestinal (GI) PNS at the time of diagnosis. Using medical records, we attempted to correlate the occurrence of these GI signs with clinical and histologic criteria, as well as to evaluate their influence on the disease-free interval (DFI) and survival (ST) over a 6-year follow-up period (2013-2020). The medical records of 41 dogs with a confirmed diagnosis of cutaneous MCT treated between 2013 and 2014 were included. All dogs underwent surgical biopsy or tumor excision, endoscopic and histologic examination to evaluate possible GI lesions. The presence and severity of GI signs were recorded. Clinical data such as the history of recurrence, number of tumors, tumor size, presence of ulceration, local pruritus, edema and erythema, histopathological classification, and mitotic index were extracted from medical records. Clinical signs relating to the GI system were observed in 41.5% of the dogs and were classified as mild in 94.1% at the time of diagnosis. Endoscopic examination of the upper digestive tract showed evidence of inflammation, but histologic examination of the mucosa showed no serious lesions in any case. There was no significant association between the occurrence of clinical GI signs and any of the variables studied. Follow-up issues meant that only 38 dogs were included for evaluation of the ST and 32 for DFI analysis. DFI was 25.1 months for dogs with GI signs and 14.8 months for dogs without GI signs. At the end of the study, 71.1% of patients had died. Survival time for dogs with GI signs was 54.9 months and 48 months for dogs without GI signs. Over the 6 years of the study, no differences were observed between the ST and the DFI, and the presence or absence of GI PNS at the time of diagnosis.

High lysyl oxidase expression is an indicator of poor prognosis in dogs with cutaneous mast cell tumours

Mast cell tumour (MCT) is one of the most frequent skin tumours in dogs. Due to their unpredictable biological behaviour, MCTs often cause several therapeutic frustrations, leading to investigation regarding prognostic markers. Lysyl oxidase (LOX) is an enzyme that promotes extracellular matrix stability and contributes to cell migration, angiogenesis and epithelial-mesenchymal transition. Its expression positively correlates with poor prognoses in several human and canine mammary cancers. The aim of this study was to characterise the immunohistochemical expression of LOX in MCT samples and compare it with histological grading and post-surgical survival. Twenty-six tumours were submitted to immunohistochemistry for LOX expression evaluation. All samples were positive for LOX, with variable percentages of cytoplasmic and nuclear positivity. Cytoplasmic positivity was significantly higher in high-grade MCTs (P = .0297). Our results indicate that high expression of cytoplasmic LOX in neoplastic mast cells is an indicator of poor prognosis for canine cutaneous MCTs.

High-Grade, Stage 2 Mast Cell Tumors: Outcome in Dogs With Local and Systemic Therapy

Canine mast cell tumors (MCTs) have highly variable clinical behavior, and predicting outcomes in individual dogs remains challenging. Many studies combine dogs with varying tumor grades, clinical stage, or treatments, confounding those results. The purpose of this retrospective study was to determine outcome and prognostic factors in a specific subset of dogs with high-grade, stage 2, cutaneous MCTs treated with adequate local control via surgery with or without radiation therapy and adjuvant cytotoxic chemotherapy. Seventeen dogs met the inclusion criteria, and the median survival time was 259 days. Development of local recurrence, tumor location, and presence of ulceration were all associated with shorter survival times. Tumor size, mitotic count, chemotherapy protocol, lymph node classification, and radiation therapy were not significantly associated with outcome. In this study, a specific population of dogs characterized by high-grade MCTs with local lymph node metastasis who received aggressive local and systemic therapy had a median survival of about 8.5 mo. Dogs with ulcerated tumors, recurrent tumors, or tumors located on the head had a worse outcome despite aggressive therapy. These results may serve as a basis of comparison for future research exploring alternative treatment combinations in this specific population of dogs.

Pan-cancer evaluation of clinical value of mitotic network activity index (MNAI) and its predictive value for immunotherapy

Increased mitotic activity is associated with the genesis and aggressiveness of many cancers. To assess the clinical value of mitotic activity as prognostic biomarker, we performed a pan-cancer study on the mitotic network activity index (MNAI) constructed based on 54-gene mitotic apparatus network. Our pan-cancer assessment on TCGA (33 tumor types, 10,061 patients) and validation on other publicly available cohorts (23 tumor types, 9,209 patients) confirmed the significant association of MNAI with overall survival, progression-free survival, and other prognostic endpoints in multiple cancer types, including lower-grade gliomas (LGG), breast invasive carcinoma (BRCA), as well as many others. We also showed significant association between MNAI and genetic instability, which provides a biological explanation of its prognostic impact at pan-cancer landscape. Our association analysis revealed that patients with high MNAI benefitted more from anti-PD-1 and Anti-CTLA-4 treatment. In addition, we demonstrated that multimodal integration of MNAI and the AI-empowered Cellular Morphometric Subtypes (CMS) significantly improved the predictive power of prognosis compared to using MNAI and CMS alone. Our results suggest that MNAI can be used as a potential prognostic biomarker for different tumor types toward different clinical endpoints, and multimodal integration of MNAI and CMS exceeds individual biomarker for precision prognosis.

Immunohistochemical and Molecular Genetic Analysis of Canine Digital Mast Cell Tumours

Grading, immunohistochemistry and c-kit mutation status are criteria for assessing the prognosis and therapeutic options of canine cutaneous mast cell tumours (MCTs). As a subset, canine digital MCTs have rarely been explored in this context. Therefore, in this retrospective study, 68 paraffin-embedded canine digital MCTs were analysed, and histological grading was assessed according to Patnaik and Kiupel. The immunohistochemical markers KIT and Ki67 were used, as well as polymerase chain reaction (PCR) for mutational screening in c-kit exons 8, 9, 11 and 14. Patnaik grading resulted in 22.1% grade I, 67.6% grade II and 10.3% grade III tumours. Some 86.8% of the digital MCTs were Kiupel low-grade. Aberrant KIT staining patterns II and III were found in 58.8%, and a count of more than 23 Ki67-positive cells in 52.3% of the cases. Both parameters were significantly associated with an internal tandem duplication (ITD) in c-kit exon 11 (12.7%). French Bulldogs, which tend to form well-differentiated cutaneous MCTs, had a higher proportion of digital high-grade MCTs and ITD in c-kit exon 11 compared with mongrels. Due to its retrospective nature, this study did not allow for an analysis of survival data. Nevertheless, it may contribute to the targeted characterisation of digital MCTs.

Caveolin-1, GATA-3, and Ki67 expressions and their correlation with pathological findings in canine bladder urothelial carcinoma

The bladder urothelial carcinoma (UC) represents ~2% of malignant neoplasms in dogs and is a therapeutic challenge in veterinary medicine. Although it is considered the most common bladder cancer in dogs, few previous studies have investigated different markers that correlate with clinical and pathological parameters. Therefore, this study aimed to evaluate Caveolin-1, GATA-3, and Ki67 immunostaining in canine UC samples to evaluate their correlations with histopathological variables. Thirty tumor samples were obtained, and Caveolin-1, GATA-3, and Ki67 expression was assessed by immunohistochemistry and associated with pathological factors by univariate and multivariate analyses. Among the histopathological findings, lymphatic invasion was identified in 53.33% of the tumors, and the mean mitotic count (MC) was 31.82 ± 26.26. Caveolin-1 showed mild-to-high cytoplasmic expression in neoplastic cells, whereas GATA-3 showed mild-to-high nuclear expression. The Ki67 expression revealed a mean of 24.14 ± 16.88% positive cells. In the univariate analysis, no association was found between each marker and the pathological findings. On the other hand, in multivariate analysis, we identified a positive correlation between GATA-3 and MC and a negative correlation between Caveolin-1 and MC. Moreover, lymphatic invasion was positively correlated with histological type and grade, and negatively correlated with MC. In addition, the histological type was positively correlated with the histological grade. Overall, our results indicate that Caveolin-1 and GATA-3 expression could be promising markers for bladder UC aggressiveness.

Exploring the association of intratumoral immune cell infiltrates with histopathologic grade in canine mast cell tumors

Cutaneous canine mast cell tumors (ccMCTs) vary in their biological behavior, treatment, and prognosis, based on their grade. Immune cell infiltration has been associated with prognosis and response to treatments in some human cancers, and immune-targeting therapeutics are increasingly being explored in veterinary oncology. However, currently little is known about the tumor microenvironment (TME) in ccMCTs. Therefore, the objective of this study was to determine the prevalence of T lymphocytes, T regulatory lymphocytes, PD-1+ cells and macrophages in low- and high-grade ccMCTs. Thirty low-grade and 20 high-grade formalin-fixed paraffin-embedded ccMCT samples were included. Immunohistochemistry (IHC) was performed to detect CD3, FOXP3, Iba1, and PD-1 on sequential sections. Three 400x fields with the highest numbers of CD3+ cells were identified for each tumor. The percentage of CD3+, FOXP3+, and Iba1+ cells, and the number of PD-1+ cells, was quantified in each of these three "hot-spot" fields using ImageJ software. Iba1 expression was significantly greater in high-grade compared to low-grade ccMCTs (mean = 12.5% vs. 9.6%, p = 0.043). PD-1 expression was low overall, but a significantly higher number of PD-1-expressing cells was observed in high-grade ccMCTs (median 1 vs. 0, p = 0.001). No significant difference was noted in CD3 and FOXP3 expression between ccMCT grades. Macrophages and PD-1+ cells were more frequent in high-grade, compared to low-grade ccMCTs. Further studies are needed to define the role of macrophages and rare PD-1+ cells in high-grade ccMCTs.

Pathological aspects of cutaneous mast cell tumors with metastases in 49 dogs

Cutaneous mast cell tumor (MCT) is one of the most frequent cutaneous neoplasms of dogs and may vary from well-differentiated to aggressive tumors with metastasis. The authors retrospectively described the gross and histologic aspects of metastatic MCT in 49 dogs. Primary MCT was most commonly identified in the inguinal region (14/35; 40%), and at necropsy multiple, cutaneous nodules were frequently reported (23/49; 47%). All primary MCT were classified as high-grade neoplasms, and metastases involved the lymph nodes (47/49; 96%), spleen (33/49; 67%), liver (29/49; 59%), bone marrow (20/49; 41%), kidneys (16/49; 33%), and heart (14/49; 29%), while the lungs were less commonly affected (9/49; 18%). The main gross findings included lymphadenomegaly in 47 cases; splenomegaly in 28 cases, with splenic nodules in 13 dogs; hepatomegaly in 28 cases, with white pinpoint foci in 9 cases; nodules on the capsular surface of the kidneys in 9 dogs; and epicardial nodules in 6 cases. Histologically, the lymph nodes were largely obliterated by neoplastic mast cells, while in the spleen, neoplastic cells were multifocally scattered (16/33; 48%), arranged in nodules (10/33; 30%), or obliterated the parenchyma (9/33; 27%). In the liver, the neoplastic cells mainly infiltrated the sinusoids (24/29; 83%), but were also arranged in random nodules (10/29; 34%). Interstitial and nodular metastases were observed in the kidneys and the heart. Grossly unapparent metastases were common in the heart (6/14; 43%), kidneys (4/16; 25%), and lungs (6/9). KIT III and KIT II staining patterns were observed in 29 and 20 cases, respectively.

Evaluation of Tumor Grade and Proliferation Indices before and after Short-Course Anti-Inflammatory Prednisone Therapy in Canine Cutaneous Mast Cell Tumors: A Pilot Study

Glucocorticoid administration is a common clinical practice that attempts to decrease the inflammation associated with and improve the resectability of canine mast cell tumors (MCTs). However, the impact of neoadjuvant glucocorticoids on the histological features and proliferation indices of canine MCTs is unknown. The objective of this study was to evaluate changes in tumor grade, mitotic count, Ki67, AgNOR, and AgNORxKi67 scores following short-course anti-inflammatory neoadjuvant prednisone in canine patients with MCTs. This was a prospective single-arm pilot study. Client-owned dogs with treatment-naïve cytologically confirmed MCTs were enrolled. Patients underwent an initial incisional biopsy followed by a 10–14-day course of anti-inflammatory prednisone and surgical resection. All histological samples were randomized, masked, and evaluated by a single pathologist. Unstained paired pre- and post-treatment samples were submitted to a commercial laboratory for Ki67 and AgNOR immunohistochemical analysis. There were 11 dogs enrolled with 11 tumors. There were no statistical differences between the pre- and post-treatment histological parameters of mitotic index, Ki67, AgNOR, or Ki67xAgNOR. There were no clinically significant alterations between pre-treatment and post-treatment in the assignment of tumor grades. A short course of anti-inflammatory prednisone does not appear to alter the histological parameters that affect grade determination or significantly alter the proliferation indices in canine MCTs.

Τhe Effect of Opioid Administration on Cytologic and Histopathologic Diagnosis of Canine Cutaneous Mast Cell Tumors Treated by Surgical Excision

Mast cell tumor (MCT) is a frequent cutaneous tumor in dogs, with a variable biological behavior. Studies correlate cytologic and histopathologic features of MCTs with their biological behavior, prognosis, and response to treatment. The use of preoperative opioids is common in canine patients undergoing surgical removal of these tumors. Certain opioids can induce or downregulate mast cell degranulation and influence cancer progression. The aim of the present study was to investigate whether the administration of morphine or butorphanol during surgical excision of canine cutaneous MCTs affects their cytologic and histopathologic appearance, thus influencing cytologic and histopathologic grading. This was a prospective, blinded, randomized, cohort clinical study. Forty-five dogs with cutaneous MCTs were randomly allocated into three groups according to preanaesthetic medication: dexmedetomidine combined with morphine (group M) or butorphanol (group B) or normal saline (group C). Cytologic specimens and histopathologic samples were obtained both prior to and after surgery. Samples were graded according to Kiupel’s and Patnaik’s systems, examined immunohistochemically for Ki-67 protein (Ki-67) and c-kit proto-oncogene product (KIT) expression, and histochemically for argyrophilic nucleolar organizing regions (AgNORs). Based on both Kiupel’s and Patnaik’s systems, no statistically significant differences were noted concerning the number of cases with grading discrepancies in grades allocated prior to versus after surgery among the groups. The same applied for cytological grading and immunohistochemical and histochemical evaluation. It seems that administration of morphine or butorphanol as part of the preanesthetic medication for surgical removal of canine cutaneous mast cell tumors does not influence histopathologic and cytologic grading of MCTs.

Diagnosis, Prognosis and Treatment of Canine Cutaneous and Subcutaneous Mast Cell Tumors

Mast cell tumors (MCTs) are hematopoietic neoplasms composed of mast cells. It is highly common in dogs and is extremely important in the veterinary oncology field. It represents the third most common tumor subtype, and is the most common malignant skin tumor in dogs, corresponding to 11% of skin cancer cases. The objective of this critical review was to present the report of the 2nd Consensus meeting on the Diagnosis, Prognosis, and Treatment of Canine Cutaneous and Subcutaneous Mast Cell Tumors, which was organized by the Brazilian Association of Veterinary Oncology (ABROVET) in August 2021. The most recent information on cutaneous and subcutaneous mast cell tumors in dogs is presented and discussed.

Computer-assisted mitotic count using a deep learning–based algorithm improves interobserver reproducibility and accuracy

The mitotic count (MC) is an important histological parameter for prognostication of malignant neoplasms. However, it has inter- and intraobserver discrepancies due to difficulties in selecting the region of interest (MC-ROI) and in identifying or classifying mitotic figures (MFs). Recent progress in the field of artificial intelligence has allowed the development of high-performance algorithms that may improve standardization of the MC. As algorithmic predictions are not flawless, computer-assisted review by pathologists may ensure reliability. In the present study, we compared partial (MC-ROI preselection) and full (additional visualization of MF candidates and display of algorithmic confidence values) computer-assisted MC analysis to the routine (unaided) MC analysis by 23 pathologists for whole-slide images of 50 canine cutaneous mast cell tumors (ccMCTs). Algorithmic predictions aimed to assist pathologists in detecting mitotic hotspot locations, reducing omission of MFs, and improving classification against imposters. The interobserver consistency for the MC significantly increased with computer assistance (interobserver correlation coefficient, ICC = 0.92) compared to the unaided approach (ICC = 0.70). Classification into prognostic stratifications had a higher accuracy with computer assistance. The algorithmically preselected hotspot MC-ROIs had a consistently higher MCs than the manually selected MC-ROIs. Compared to a ground truth (developed with immunohistochemistry for phosphohistone H3), pathologist performance in detecting individual MF was augmented when using computer assistance (F1-score of 0.68 increased to 0.79) with a reduction in false negatives by 38%. The results of this study demonstrate that computer assistance may lead to more reproducible and accurate MCs in ccMCTs.

Outcomes of adjunctive radiation therapy for the treatment of mast cell tumors in dogs and assessment of toxicity: A multicenter observational study of 300 dogs

Background

Radiation therapy is commonly used as an adjunct to incomplete surgical excision in dogs with mast cell tumors (MCT), but the optimal dose and fractionation regimen have yet to be determined.

Hypothesis

We assessed outcomes (time to local recurrence, patient survival and toxicity) of a large population of dogs with MCT that received adjunctive radiation therapy.

Animals

Three hundred dogs with 302 MCT treated using adjunctive radiation therapy.

Methods

Retrospective observational study. Clinical records of 4 veterinary radiation centers were reviewed.

Results

Local recurrence rates were similar regardless of radiation protocol with 6.6% of patients developing recurrent cutaneous MCT at a median of 526 days. Local recurrence rate was similar between high and low‐risk MCT. Mast cell tumor related death was reported in 19% of all dogs, with 13% of dogs with low‐risk MCT dying of their disease compared to 29% of dogs with high‐risk MCT. No SC MCT (SCMCT) recurred after radiation therapy and only 7% of dogs with SCMCT were reported to have died of their disease. Mild late toxicity was common in both protocols and severe late toxicity occurred in 1.9% of dogs many years after treatment.

Conclusions and Clinical Importance

Our study supports the use of adjunctive radiation for the long‐term control of incompletely or narrowly excised cutaneous and SCMCT in dogs. More moderate dose and fractionation protocols may be appropriate in the adjunctive treatment of low‐risk MCT in dogs. Large multicenter prospective studies are required to establish the optimal dose and fractionation for MCT of different risk categories.

Canine cutaneous and subcutaneous mast cell tumours: a review

Cutaneous and subcutaneous mast cell tumours are common neoplasms in the dog. While the majority can be treated with adequate local therapy alone, a subset demonstrates a biologically aggressive behaviour associated with local recurrence or metastasis. This article reviews the diagnosis and tumour staging of canine mast cell tumours alongside treatment options and the evidence supporting their use. In addition, prognostic markers are evaluated to highlight how one can recognise mast cell tumours that may behave in a biologically aggressive manner as well as the challenges of tumours that are large, infiltrative or in locations not amenable to wide surgical excision.

International Guidelines for Veterinary Tumor Pathology: A Call to Action

Standardization of tumor assessment lays the foundation for validation of grading systems, permits reproducibility of oncologic studies among investigators, and increases confidence in the significance of study results. Currently, there is minimal methodological standardization for assessing tumors in veterinary medicine, with few attempts to validate published protocols and grading schemes. The current article attempts to address these shortcomings by providing standard guidelines for tumor assessment parameters and protocols for evaluating specific tumor types. More detailed information is available in the Supplemental Files, the intention of which is 2-fold: publication as part of this commentary, but more importantly, these will be available as "living documents" on a website (www.vetcancerprotocols.org), which will be updated as new information is presented in the peer-reviewed literature. Our hope is that veterinary pathologists will agree that this initiative is needed, and will contribute to and utilize this information for routine diagnostic work and oncologic studies. Journal editors and reviewers can utilize checklists to ensure publications include sufficient detail and standardized methods of tumor assessment. To maintain the relevance of the guidelines and protocols, it is critical that the information is periodically updated and revised as new studies are published and validated with the intent of providing a repository of this information. Our hope is that this initiative (a continuation of efforts published in this journal in 2011) will facilitate collaboration and reproducibility between pathologists and institutions, increase case numbers, and strengthen clinical research findings, thus ensuring continued progress in veterinary oncologic pathology and improving patient care.

Value, Limitations, and Recommendations for Grading of Canine Cutaneous Mast Cell Tumors: A Consensus of the Oncology-Pathology Working Group

One of the primary objectives of the Oncology Pathology Working Group (OPWG), a joint initiative of the Veterinary Cancer Society and the American College of Veterinary Pathologists, is for oncologists and pathologists to collaboratively generate consensus documents to standardize aspects and provide guidelines for oncologic pathology. Consensus is established through review of relevant peer-reviewed literature relative to a subgroup's particular focus. In this article, the authors provide a critical review of the current literature for grading of canine cutaneous mast cell tumors, suggest guidelines for reporting, and provide recommendations for its clinical interpretation. The article mainly focuses on histologic grading, but relevant information on mitotic count and cytological grading are also discussed. This document represents the opinions of the working group and the authors but does not constitute a formal endorsement by the American College of Veterinary Pathologists or the Veterinary Cancer Society.

RNAScope in situ Hybridization as a Novel Technique for the Assessment of c-KIT mRNA Expression in Canine Mast Cell Tumor

RNA is considered as an indicator of the dynamic genetic expression changes in a cell. RNAScope is a commercially available in situ hybridization assay for the detection of RNA in formalin-fixed paraffin-embedded tissue. In this work, we describe the use of RNAScope as a sensitive and specific method for the evaluation of c-KIT messenger RNA (mRNA) in canine mast cell tumor. We investigated the expression of c-KIT mRNA with RNAscope in 60 canine mast cell tumors (MCTs), comparing it with the histological grade and KIT immunohistochemical expression patterns. Our results showed an overall good expression of c-KIT mRNA in neoplastic cells if compared with control probes. We also observed a statistically significant correlation between histological grade and c-KIT mRNA expression. No correlations were found between KIT protein immunohistochemical distribution pattern and c-KIT mRNA expression or histological grade. Our results provide a reference basis to better understand c-KIT mRNA expression in canine MCTs and strongly encourage further studies that may provide useful information about its potential and significant role as a prognostic and predictive biological marker for canine MCTs clinical outcome.

Outcome of dogs with intermediate grade low mitotic index high Ki67 mast cell tumours treated with surgery and single agent lomustine

OBJECTIVES

The objective of this retrospective study was to evaluate the outcome of dogs when grade II mast cell tumour (MCT) with low mitotic index (MI) and high Ki67 were treated with adjuvant lomustine.

ANIMALS

Client owned dogs with spontaneously occurring disease treated with adjuvant chemotherapy for grade II mast cell tumour with low MI (≤5/10HPF) and high Ki67 (>1.8%) with no evidence of metastatic disease at presentation.

PROCEDURES

Lomustine was administered every 3 weeks with three or four planned cycles. Response to treatment was assessed by regular re-staging ultrasound with or without cytopathological examination of liver and spleen or through medical records from the referring veterinarian. Disease-free interval (DFI) and median survival time (MST) were calculated using Kaplan-Meier method.

RESULTS

Twenty-one dogs were included. All dogs underwent surgical excision and two dogs received adjuvant radiotherapy. None of the patients developed local recurrence. Three dogs (14.3%) developed metastatic disease. The DFI of these dogs was 141, 186 and 223 days. Median follow-up period of the whole study population was 1112 days (358-2619). MST for patients with metastatic disease was 417 days. MST of the whole group was not reached. One-year and 2-year survivals were 95.2% and 90.5%, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

This study population had low rates of tumour recurrence and improved survival compared to previously published data of similar population of dogs with low MI/high Ki67 MCT without adjuvant chemotherapy.

Evaluation of ponatinib in vitro effect in three canine mast cell tumor cell lines expressing FGFR-1, PDGFR-α, and VEGFR-2

Ponatinib is a broad-spectrum tyrosine kinase inhibitor that targets numerous receptor tyrosine kinases (RTKs), including but not limited to fibroblast growth factor receptor (FGFR)-1, platelet derived growth factor receptor (PDGFR)-α, and vascular endothelial growth factor receptor (VEGFR)-2. This study evaluated the expression of FGFR-1, PDGFR-α, and VEGFR-2 in three canine mast cell tumor (MCT) cell lines (CM-MC1, VI-MC1, CoMS) and the effects of ponatinib on these MCT cell lines. Quantitative RT-PCR confirmed the expression of FGFR-1, PDGFR-α, and VEGFR-2 in the three MCT cell lines. Ponatinib exhibited dose- and time-dependent cytotoxicity in MCT cell lines via MTT assay. The IC₅₀ for 24, 48, and 72 h across the three cell lines ranged from 38.47 nM to 103.3 nM, which is clinically comparable to dose ranges established for humans. Significantly increased apoptosis in each cell line was seen between 12 and 18 h after treatment with IC₅₀ of ponatinib via Annexin-V and Caspase-3/7 assays. These data suggest that ponatinib could be a possible therapeutic agent for canine MCTs. Further studies are needed to investigate the prognostic value of FGFR-1, PDGFR-α, and VEGFR-2 in canine MCTs.

Internal Tandem Duplication of Exon 8 of c-kit Is Associated With Longer Total Survival in Canine Cutaneous Mast Cell Tumors

Canine cutaneous mast cell tumors (ccMCTs) have a highly variable biological behavior and accurate prognostication is essential for therapeutic intervention. Internal tandem duplications (ITD) of exon 11 are the most commonly detected c-kit mutation in ccMCTs and are associated with poor prognosis and increased cellular proliferation. The prognostic value of detecting mutations in other exons of c-kit has not been systematically examined. In this study, we analyzed the prognostic value of ITD mutations of exon 8 in c-kit of ccMCTs in comparison to ccMCTs with ITD mutations of exon 11 and ccMCTs without mutations of exon 8 or 11. The mutational status, histological grade, KIT expression pattern, Ki67 index, AgNOR (argyrophilic nucleolar organizing region) score, and Ag67 score were determined in 221 ccMCTs, and outcome was available for 101 dogs. ITD mutations of exon 8 were found in 73/221 (33%), of exon 11 in 100/221 (45%), and none of these mutations in 50/221 (22%) of ccMCTs. None of the dogs with mutations of exon 8 died due to suspected ccMCT-related cause, but 23% dogs with ccMCTs with mutations of exon 11 died due to suspected ccMCT-related cause. Prognostic parameters in ccMCTs with exon 11 mutations were commonly associated with a high proliferative activity and poor prognosis, while prognostic markers in ccMCTs with mutations of exon 8 had lower values similar to those observed in ccMCTs without mutations in exons 8 or 11 of c-kit. This study indicates that screening for ITD mutations in exon 8 in ccMCTs may be helpful to identify less aggressive ccMCTs and may be recommended as a supplementary prognostic test.

In situ c-KIT mRNA quantification of canine cutaneous mast cell tumours and its relationship to prognostic factors

Cutaneous mast cell tumours (MCTs) are the most frequent malignant skin tumours in dogs. Mutations in the c-KIT proto-oncogene are correlated with the pathogenesis and aggressiveness of MCTs. To date, studies have focused on c-KIT mutations and KIT protein localization, with a general lack of mRNA-level analyses. In this study, c-KIT mRNA expression was investigated in canine MCTs by RNA in situ hybridization (RNA-ISH). Furthermore, we evaluated associations between c-KIT mRNA expression and the histological grade, KIT immunohistochemical staining pattern and other clinicopathological parameters. c-KIT mRNA expression was observed in all MCT samples, appearing as clusters of dots in the cytoplasm of neoplastic cells. A significant correlation was detected between c-KIT mRNA expression (quantified according to the H-score and the percentage of positive cells) and the histological grade (determined using two-and three-tier grading systems; P < .05). We also found a significant positive correlation (all P < .05) between c-KIT mRNA expression and the proliferation indices (mitotic index, Ki-67, and Ag67). However, no significant associations with c-KIT expression from RNA-ISH were found with respect to different KIT staining patterns. Overall, these results demonstrate that c-KIT mRNA expression might be an additional tool for measuring the c-KIT status in canine cutaneous MCTs and could serve as a potential prognostic factor. Further studies should evaluate the prognostic significance of c-KIT mRNA expression in a large and uniform cohort of canine MCTs.

Mast cell tumours in dogs less than 12 months of age: a multi-institutional retrospective study

OBJECTIVES

To describe the clinicopathological and genetic characteristics of mast cell tumours in dogs less than 12 months old.

MATERIALS AND METHODS

Retrospective review of dogs aged less than 12 months when diagnosed with mast cell tumours at three referral hospitals in the UK.

RESULTS

Sixteen pure-bred dogs were included, of which 11 were female. The median age at first presentation and diagnosis were 7.6 and 9 months, respectively. In 13 dogs the mast cell tumours were cutaneous and in three they were subcutaneous. Four cutaneous mast cell tumours were described as high-grade (Patnaik or Kiupel) and nine were Patnaik grade II; three had mitotic index of >5 in 10 high-power fields. Of the three subcutaneous tumours, two had an infiltrative growth pattern and one had mitotic index of 10 per 10 high-power fields. Of 10 tested dogs, seven had c-kit mutations in exon 11 and Ki-67 score was above the cut-off value in nine. Four of 12 cases showed evidence of metastasis in the regional lymph nodes. After varying treatment protocols, all patients were alive and disease free at a median of 1115 days after diagnosis.

CLINICAL SIGNIFICANCE

The prognosis of mast cell tumours in dogs less than a year old appears better than the adult counterparts, even without extensive treatment.

Canine and Feline Cutaneous Mast Cell Tumor: A Comprehensive Review of Treatments and Outcomes

Mast cell tumor (MCT) or mastocytoma is one of the most frequent malignant cutaneous tumors in the dog, and the second most frequent in the cat. Several mast cell tumor therapeutic approaches have been proposed in the past years for dogs and cats, resulting in very distinct outcomes. The current comprehensive literature review presents a critical approach to the scientific information published about the MCTs treatments and the subsequent prognosis and survival times, in dogs and in cats diagnosed with MCTs. A systematic review of the literature following the Cochrane principles and methodology was performed. The authors resorted to MEDLINE, Scopus, Google Scholar and Web of Science databases to select the 133 publications with evidence-based treatments for MCTs in companion animals. Results of the review suggest that the recommended treatment, prognosis and survival times for dogs and cats with MCTs depends at all times on the clinical staging, histological grade and location of the tumor.

Prognostic Indicators and Clinical Outcome in Dogs with Subcutaneous Mast Cell Tumors Treated with Surgery Alone: 43 Cases

The purpose of this study was to determine if clinical findings, histologic grade, or other histologic features were associated with clinical outcome in dogs with subcutaneous mast cell tumors (MCTs). Medical records of 43 client-owned dogs were retrospectively reviewed, and follow-up information was gathered via phone or follow-up examination. Progression-free survival (PFS), disease-free interval (DFI), and overall survival were calculated. Forty-two and twenty-two dogs, respectively, had grade 2 (Patnaik grading system) or low-grade tumors (two-tier grading system). Median PFS was 1474 days. Median DFI was not reached at >1968 days. Overall median survival time was not reached at >1968 days. In univariate analysis, argyrophilic nucleolar organizer regions (AgNORs), proliferating cell nuclear antigen, and mitotic index were negatively prognostic for PFS whereas Ki-67, proliferating cell nuclear antigen, and microvessel density were negatively prognostic for DFI. In multivariate analysis, AgNORs remained negatively prognostic for PFS. Results suggest that proliferation indices, especially AgNORs, may be useful in predicting the rare poor outcomes in dogs with subcutaneous MCTs. The vast majority of subcutaneous MCTs appear to be low or intermediate grade with excellent outcomes from good local tumor control.

Fluorescence-guided surgery using indocyanine green in dogs with superficial solid tumours

BACKGROUND

Near-infrared fluorescence (NIRF) imaging is a relatively novel technique that can aid surgeons during intraoperative tumour identification.

METHODS

Nine canine oncology patients (five mammary gland tumours, three mast cell tumours and one melanoma) received intravenous indocyanine green (ICG). After 24 hours, tumours were resected and fluorescence intensities of tumours and surroundings were evaluated. Additional wound bed tissue was resected if residual fluorescence was present after tumour resection. Ex vivo, fluorescence-guided dissection was performed to separate tumour from surrounding tissue.

RESULTS

Intraoperative NIRF-guided tumour delineation was feasible in four out of nine dogs. Wound bed imaging after tumour removal identified nine additional fluorescent lesions, of which four contained tumour tissue. One of these four true positive in vivo lesions was missed by standard-of-care inspection. Ex vivo fluorescence-guided tumour dissection showed a sensitivity of 72 per cent and a specificity of 80 per cent in discriminating between tumour and surrounding tissue.

CONCLUSION

The value of ICG for intraoperative tumour delineation seems more limited than originally thought. Although NIRF imaging using ICG did identify remaining tumour tissue in the wound bed, a high false positive rate was also observed.

Clinicopathological characteristics and prognostic factors for canine multicentric non-indolent T-cell lymphoma: 107 cases

Canine lymphoma, as the most common haematopoietic malignancy, encompasses a group of heterogeneous diseases and even within the T-cell immunophenotype, differences in clinical presentation and responses to treatment exist. The aim of this retrospective study was to determine outcomes and prognostic factors of 107 dogs with multicentric non-indolent T-cell lymphoma (TCL) receiving lomustine-based (70%) and non-lomustine-based (30%) treatment. The majority were Labradors, Boxers, mixed-breed dogs and Dogue de Bordeaux. Eighty-six percent were substage b, 77% had mediastinal involvement, 15% had suspected bone marrow involvement and 12% had other extra-nodal sites of disease. The overall response rate to induction therapy was 80%; dogs receiving procarbazine in the induction protocol (P = .042), dogs with neutrophil concentration below 8.7 × 10e⁹ /L (P = .006) and mitotic rate below 10 per 5 high power field (P = .013), had greater response rates. Median progression-free survival (PFS) for the first remission was 105 days; lack of expression of CD3 on flow cytometry (P < .0001) and pretreatment with steroid (P = .012) were significantly associated with shorter PFS. Median overall survival time (OST) was 136 days; co-expression of CD79a (P = .002), lack of CD3 expression on flow cytometry, presence of anaemia (P = .007), and monocytopenia (P = .002) were predictive of shorter OST. Multicentric non-indolent TCL in dogs is an aggressive cancer with new possible prognostic factors.

Histologically low-grade, yet biologically high-grade, canine cutaneous mast cell tumours: A systematic review and meta-analysis of individual participant data

Low-grade canine cutaneous mast cell tumour (cMCT) with metastasis at the time of treatment is uncommonly reported, with few studies focusing on this specific clinical entity. The specific objective of this study was to systematically review the veterinary literature and perform a meta-analysis summarizing the clinical presentation, treatments reported and clinical outcomes from dogs with histologically low-grade cMCT and metastasis present at initial treatment. A total of 980 studies were screened with eight publications providing data on 121 dogs ultimately included. The most common treatments were surgery with adjuvant chemotherapy in 83/121 (69%) dogs; combined surgery, radiation and chemotherapy in 17/121 (14%) dogs; chemotherapy alone in 12/121 (10%) dogs and surgery alone in 7/121 (6%) dogs. Dogs with distant metastasis (n = 22) experienced significantly shorter survival compared with those with regional lymph node (RLN) metastasis (n = 99; median 194 vs 637 days; P < .01). Two variables were significantly associated with increased risk of death: presence of distant (vs RLN) metastasis (hazard ratio = 2.60; P < .01) and not receiving surgery as a component of treatment (hazard ratio = 3.79; P < .01). Risk of bias was judged to be low in terms of selection and performance bias but high in terms of detection and exclusion bias. In conclusion, dogs with cMCT and RLN metastasis can be expected to live significantly longer than those with distant metastasis, and surgery appears to have a role in extending survival of metastatic low-grade cMCT.

Retrospective outcome evaluation for dogs with surgically excised, solitary Kiupel high-grade, cutaneous mast cell tumours

Published outcomes for dogs with specifically high-grade mast cell tumours (MCTs), controlled for clinical stage, are few. Clinical outcomes for 49 dogs with Kiupel high-grade, clinical stage I, cutaneous MCTs were evaluated. Median survival time (MST) was 1046 days; 1 and 2-year survival rates were 79.3% and 72.9%, respectively. At study end 24 dogs had died, 23 dogs were alive (median follow-up 980 days) and 2 dogs were lost to follow-up. Death was considered MCT-related in 14 of 20 dogs with a known cause of death. Local tumour recurrence developed in nine dogs (18.4%); regional lymph node metastasis occurred in six dogs (12.2%); and a new MCT developed in 15 dogs (30.1%). Tumour location, histologic margin size and use of chemotherapy did not affect MST; increasing mitotic count (P = .001) and increasing tumour diameter (P = .024) were independently negatively prognostic. Six dogs that developed lymph node metastasis after surgery had worse MST (451 days) than 42 dogs that did not develop metastasis (1645 days); (P < .001). Our study suggests that dogs with local surgical control of clinical stage I histologically high Kiupel grade cutaneous MCT may have a long survival time; especially those with smaller tumours and a lower mitotic count. Our results suggest that evaluation of staging information and mitotic count may be equally helpful as histologic grading when making a prognosis; and highlight the importance of not relying on histologic grade alone when predicting survival for dogs with MCT.

Ultrasound is a poor predictor of early or overt liver or spleen metastasis in dogs with high-risk mast cell tumours

Conflicting evidence exists regarding the importance of routine abdominal ultrasound (US) with hepatic and splenic fine needle aspiration (FNA) cytology during staging of canine mast cell tumours (MCT). The objective of this study was to correlate ultrasonographic and cytologic findings in dogs with strictly defined high-risk MCTs and to determine the influence on outcome. Our hypothesis was that US poorly predicts visceral metastasis in high-risk MCTs and that early metastasis is associated with improved outcome when compared to overt metastasis. US of liver and spleen correlated to cytologic results, categorized as no metastasis, early metastasis or overt metastasis. Of 82 dogs prospectively enrolled, 18% had early visceral metastasis and 7% had overt metastasis on cytology; 67% with visceral metastasis had regional LN metastasis. US was a poor predictor of metastasis with sensitivity, specificity, positive predictive value and negative predictive value for the spleen of 67%, 68%, 21% and 94%, respectively and for the liver of 29%, 93%, 56% and 82%, respectively. Median time to progression (TTP) for dogs with no metastasis, early metastasis and overt metastasis was not reached, 305 and 69 days, respectively (P < .001). Median survival time (MST) for the 3 groups were not reached, 322 and 81 days, respectively (P < .001). High Patnaik or Kiupel grade, early metastasis, overt metastasis and adequate local control were significantly associated with outcome. Early visceral metastasis was associated with poorer outcome compared to dogs without metastasis, however, a subset of dogs experienced long-term control.

Computerized Calculation of Mitotic Count Distribution in Canine Cutaneous Mast Cell Tumor Sections: Mitotic Count Is Area Dependent

Mitotic count (MC) is an important element for grading canine cutaneous mast cell tumors (ccMCTs) and is determined in 10 consecutive high-power fields with the highest mitotic activity. However, there is variability in area selection between pathologists. In this study, the MC distribution and the effect of area selection on the MC were analyzed in ccMCTs. Two pathologists independently annotated all mitotic figures in whole-slide images of 28 ccMCTs (ground truth). Automated image analysis was used to examine the ground truth distribution of the MC throughout the tumor section area, which was compared with the manual MCs of 11 pathologists. Computerized analysis demonstrated high variability of the MC within different tumor areas. There were 6 MCTs with consistently low MCs (MC<7 in all tumor areas), 13 cases with mostly high MCs (MC ≥7 in ≥75% of 10 high-power field areas), and 9 borderline cases with variable MCs around 7, which is a cutoff value for ccMCT grading. There was inconsistency among pathologists in identifying the areas with the highest density of mitotic figures throughout the 3 ccMCT groups; only 51.9% of the counts were consistent with the highest 25% of the ground truth MC distribution. Regardless, there was substantial agreement between pathologists in detecting tumors with MC ≥7. Falsely low MCs below 7 mainly occurred in 4 of 9 borderline cases that had very few ground truth areas with MC ≥7. The findings of this study highlight the need to further standardize how to select the region of the tumor in which to determine the MC.

A large-scale dataset for mitotic figure assessment on whole slide images of canine cutaneous mast cell tumor

We introduce a novel, large-scale dataset for microscopy cell annotations. The dataset includes 32 whole slide images (WSI) of canine cutaneous mast cell tumors, selected to include both low grade cases as well as high grade cases. The slides have been completely annotated for mitotic figures and we provide secondary annotations for neoplastic mast cells, inflammatory granulocytes, and mitotic figure look-alikes. Additionally to a blinded two-expert manual annotation with consensus, we provide an algorithm-aided dataset, where potentially missed mitotic figures were detected by a deep neural network and subsequently assessed by two human experts. We included 262,481 annotations in total, out of which 44,880 represent mitotic figures. For algorithmic validation, we used a customized RetinaNet approach, followed by a cell classification network. We find F1-Scores of 0.786 and 0.820 for the manually labelled and the algorithm-aided dataset, respectively. The dataset provides, for the first time, WSIs completely annotated for mitotic figures and thus enables assessment of mitosis detection algorithms on complete WSIs as well as region of interest detection algorithms.

Phosphorylated KIT as a predictor of outcome in canine mast cell tumours treated with toceranib phosphate or vinblastine

Canine cutaneous mast cell tumour (MCT) is the most common malignant skin tumour in dogs and can exhibit variable biologic behaviour. Dysregulated signalling through the receptor tyrosine kinase (RTK) KIT can promote cell proliferation and survival, and assessment of its dysregulation via detection of activating c-kit gene mutations or assessment of KIT protein localization is associated with multiple features of malignancy. The aim of the current study was to use a previously validated immunohistochemical (IHC) assay to directly measure phosphorylated KIT (pKIT) in order to investigate its association with other established prognostic markers, response to therapy, progression free interval (PFI) and overall survival time (OST) in dogs treated medically for measurable MCT. Tumour tissue from 74 dogs enrolled in a prospective study comparing toceranib and vinblastine for MCT treatment were evaluated for pKIT immunoreactivity. pKIT was variably expressed, with some degree of positivity observed in 49/74 cases (66%). pKIT immunoreactivity was significantly associated with aberrant KIT localization, high mitotic index and high histologic grade. On univariate analysis, pKIT immunoreactivity predicted shorter PFI and OST in the entire patient population as well as shorter PFI in the toceranib treated group, and was the sole predictive factor for OST upon multivariate analysis, while mitotic index was the sole independent predictive factor for PFI. These results demonstrate that IHC detection of pKIT correlates with several features of aggressive behaviour, and may confer information that is complementary to other prognostic factors. However, the role of pKIT in predicting outcome needs to be studied further before recommendations can be made for its routine use.

Patient and tumour factors influencing canine mast cell tumour histological grade and mitotic index

The aim of this study was to identify patient and tumour factors most frequently associated with high histological grades of canine mast cell tumours (MCTs). Search criteria in a shared database of multiple Animal Referral Hospital locations within Australia generated 400 canine MCTs in 286 patients. Patient and tumour data were extrapolated and the association between a tumour being histologically high grade and patient and tumour factors, including: patient breed, patient gender and neuter status, patient age at MCT excision, tumour location and tumour size was assessed using univariate analysis. The study consisted of 90 (21.9%) tumours meeting histological high-grade criteria. Shar peis were the most likely breed to have high grade MCTs, whereas the Pug and the Golden Retriever were the least likely breeds to develop high-grade MCTs. No significant difference in risks could be established between the age at which the tumour was excised, or the gender and neuter status of patients. MCTs of the inguinal region were the most likely single location to be high grade. Tumour size did not influence the likelihood of a tumour being high grade or low grade. The results of this study suggest that patient and tumour factors may play a role in the histological grades of canine MCTs.

Intratumoral collagen index predicts mortality and survival in canine cutaneous mast cell tumours

BACKGROUND

Mast cell tumours (MCTs) constitute almost 25% of cutaneous neoplasms in dogs. Their biological behaviour is predicted using histopathological grading which is based on several subjective criteria that are vulnerable to intra- and interobserver variability. To improve the prediction of the biological behaviour, several complementary markers have been studied. The integrity of the extracellular matrix (ECM) may play a protective role against tumoral progression, and favour cellular proliferation, angiogenesis, invasion and metastases when altered.

HYPOTHESIS/OBJECTIVES

To evaluate the quantification of collagen and elastic fibres as prognostic markers for MCTs.

ANIMALS

Thirty-eight random cases of canine cutaneous MCT surgically treated with wide margins were included.

METHODS AND MATERIALS

Intratumoral collagen and elastic fibres were identified and quantified on histological sections stained with Masson's trichrome, Picrosirius red and Verhoeff; the results were compared with histopathological grades, mortality due to the disease and postsurgical survival.

RESULTS

Morphometric analysis revealed a significant relationship between histopathological grade and intratumoral collagen index (CoI). In addition, the CoI was considered an independent indicator for mortality and postsurgical survival.

CONCLUSIONS AND CLINICAL IMPORTANCE

These results support the importance of the CoI in the grading and prognosis of MCTs, suggesting that preservation and/or synthesis of collagen have the potential to become targets for MCT therapeutics.

Identification of molecular genetic contributants to canine cutaneous mast cell tumour metastasis by global gene expression analysis

Cutaneous mast cell tumours are one of the most common canine cancers. Approximately 25% of the tumours metastasise. Activating c-kit mutations are present in about 20% of tumours, but metastases occur in the absence of mutations. Tumour metastasis is associated with significantly diminished survival in spite of adjuvant chemotherapy. Available prognostic tests do not reliably predict whether a tumour will metastasise. In this study we compared the global expression profiles of 20 primary cutaneous mast cell tumours that metastasised with those of 20 primary tumours that did not metastasise. The objective was to identify genes associated with mast cell tumour metastatic progression that may represent targets for therapeutic intervention and biomarkers for prediction of tumour metastasis. Canine Gene 1.1 ST Arrays were employed for genome-wide expression analysis of formalin-fixed, paraffin-embedded biopsies of mast cell tumours borne by dogs that either died due to confirmed mast cell tumour metastasis, or were still alive more than 1000 days post-surgery. Decreased gene expression in the metastasising tumours appears to be associated with a loss of cell polarity, reduced cell-cell and cell-ECM adhesion, and increased cell deformability and motility. Dysregulated gene expression may also promote extracellular matrix and base membrane degradation, suppression of cell cycle arrest and apoptosis, and angiogenesis. Down-regulation of gene expression in the metastasising tumours may be achieved at least in part by small nucleolar RNA-derived RNA and microRNA-effected gene silencing. Employing cross-validation, a linear discriminant analysis-based classifier featuring 19 genes that displayed two-fold differences in expression between metastasising and non-metastasising tumours was estimated to classify metastasising and non-metastasising tumours with accuracies of 90-100% and 70-100%, respectively. The differential expression of 9 of the discriminator genes was confirmed by quantitative reverse transcription-PCR.

Evaluation of Histological, Immunohistochemical, Clinical and Genetic Prognostic Factors Associated with the Response of Canine Mast Cell Tumours to Glucocorticotherapy

Mast cell tumours (MCTs) are one of the most frequent neoplasms in dogs. Glucocorticoids (GCs) are widely used in the management of this disease, although no guidelines for their use have been established. The aim of this study was to evaluate the correlation of MCT prognostic factors with measurable response to GCs. This retrospective study included 60 dogs treated with prednisone or prednisolone prior to surgical biopsy of MCT. Incisional or excisional biopsy was performed 7-14 days after initiation of GC therapy. Histopathology, immunohistochemical labelling for Ki67 and KITr, and polymerase chain reaction for the c-KIT gene were performed. Partial response occurred in 63.3% of cases (38/60), while 36.7% (22/60) did not respond. A response to GCs was correlated with lower stage of the disease, low histological grade, lower pattern of KITr expression and Ki67 score. Response to GCs was positively correlated with well-established favourable prognostic factors.

Epidemiological assessment of the risk of canine mast cell tumours based on the Kiupel two-grade malignancy classification

Background

The degree of differentiation of mast cell tumours (MCTs) is the most important feature and reflects the morphological characteristics and metastatic potential of the tumour and its likely response to treatment and the prognosis. The aim of this study was to epidemiologically analyse the risk of MCT development in dogs according to breed, age, sex, size and anatomical location of the tumour using the Kiupel grading system. The analysis involved 492 dogs selected based on a histopathological assessment of 2763 canine skin tumours. A logistic regression analysis was performed to determine the odds ratios (ORs) with 95% confidence intervals.

Results

Mast cell tumours accounted for 17.8% of all diagnosed canine skin tumours. The highest risk of high-grade MCTs was noted in the Shar-Pei (OR 28.18, P < 0.001) and Weimaraner (OR 6.45, P = 0.023). The highest risk of low-grade MCTs was determined in the Boxer (OR 6.72, P < 0.001), and Pug (OR 6.13, P = 0.027). The scrotum (OR 31.72, P < 0.001), inguinal area (OR 17.69, P < 0.001) and axilla (OR 6.30, P < 0.001) had the highest risk of high-grade MCTs. The risk of high-grade MCTs increased with age and peaked in the oldest dogs, aged 11–16 years (OR 9.55, P < 0.001). A higher risk of low-grade tumours was noted in younger dogs (aged 4–6 years) (OR 8.54, P < 0.001) and females (OR 1.43, P = 0.001). Statistical analysis further revealed a higher risk of both low (OR 3.47, P < 0.001) and high-grade MCTs (OR 1.71, P = 0.006) in medium-sized dogs.

Conclusions

This study demonstrated relationships between Kiupel grading system and phenotypic traits, age and location of canine MCTs confirming the complex biological nature of this tumour.

Electronic supplementary material

The online version of this article (10.1186/s13028-018-0424-2) contains supplementary material, which is available to authorized users.

Prognostic significance of histopathology in canine anal sac gland adenocarcinomas: Preliminary results in a retrospective study of 39 cases

Metastatic rates and survival times of canine anal sac gland adenocarcinomas (ASGACs) vary among studies, making prognostication difficult. Little is known about the prognostic significance of histopathology of ASGACs. This retrospective study investigated associations between histological features, clinical presentation and outcome for 39 ASGACs. Most tumours were incompletely excised (62%) and had moderate to marked peripheral infiltration (74%). The predominant growth pattern was solid, tubules/rosettes/pseudorosettes and papillary in 49%, 46% and 5% of the cases, respectively. Nuclear pleomorphism was either moderate (77%) or mild (23%). Necrosis and lymphovascular invasion were present in 54% and 10% of the cases, respectively. All histological features except mitotic count and necrosis were associated with nodal metastasis at presentation. A statistically significant poorer outcome was identified for tumours with a solid growth pattern, moderate or marked peripheral infiltration, necrosis and lymphovascular invasion. These results need further validation in a larger cohort of dogs.

Evaluation of information presented within mast cell tumour histopathology reports in the United States: 2012-2015

For canine mast cell tumour (MCT), histopathology reports are one of the main factors considered in the decision-making process regarding need and type of adjunctive therapy. However, considerable variation exists in types of information reported, especially relating to surgical margins. The purpose of this study was to describe and evaluate how information is presented within canine MCT histopathology reports across the United States. The reports were collected from medical and surgical oncologists from 4 geographic regions of the USA: Midwest, Northeast, South and West. All reports were obtained between January 1st 2012 and May 1st 2015. Inclusion criteria required that the final diagnosis was MCT, a microscopic description was present, and it was not a scar revision. Three hundred and sixty-eight reports were collected from 26 contributors. While the majority of the reports contained a clinical history (85.9%), information for certain prognostic indicators such as location and mass size was lacking. Grading with both Patnaik and Kiupel systems were described in 76.5% of reports with a single system being used in 7.1% and 15.2% of reports, respectively. Subcutaneous MCT were assigned a grading scheme in 67.2% of reports with 33.3% stating appropriate limitations. Surgical margins were reported in 92% of the reports with 77.2% describing deep and lateral margins separately. Tissue composing the deep margin was only described in 10.9% of the reports. The present results indicate reporting of MCT has variability across pathologists with inconsistencies present in the reporting of clinical history, margin evaluation and subcutaneous MCT grading.

Oncolytic Sendai Virus Therapy of Canine Mast Cell Tumors (A Pilot Study)

Background: Canine mastocytomas (mast cell tumors) represent a common malignancy among many dog breeds. A typical treatment strategy for canine mastocytomas includes surgery, chemo- and radio-therapy, although in many cases the therapy fails and the disease progression resumes. New treatment approaches are needed. Aims: The goal of this pilot study was to examine safety and efficacy of oncolytic Sendai virus therapy administered to canine patients with cutaneous or subcutaneous mastocytomas. Materials and Methods: Six canine patients, with variable grades and stages of the disease, received virus therapy, either as a monotherapy, or in combination with surgery. The therapy included two or more virus applications administered weekly or biweekly. Each application of Sendai virus (107-108.6 EID50) consisted of multiple individual 0.01-0.1 ml injections delivered intratumorally, intradermally around a tumor, and under a tumor bed. Results: The treatment was well tolerated, with minor transitory side effects. Of the six dogs, two did not receive surgery or any other treatment besides the virus injections. The other four animals underwent radical or debulking surgeries, and in three of them the subsequent administration of Sendai virus completely cleared locally recurrent or/and remaining tumor masses. Five dogs demonstrated a complete response to the treatment, the animals remained disease free during the time of observation (2-3 years). One dog responded only partially to the virotherapy; its after-surgical recurrent tumor and some, but not all, metastases were cleared. This dog had the most advanced stage of the disease with multiple enlarged lymph nodes and cutaneous metastases. Conclusion: The results of the pilot study suggest that Sendai virus injections could be safe and efficient for the treatment of dogs affected by mastocytomas.They also suggest the need of further studies for finding optimal schemes and schedules for this kind of therapy.