Proposed Diagnostic Criteria and Classification of Canine Mast Cell Neoplasms: A Consensus Proposal

TurboID-Based IRE1 Interactome Reveals Participants of the Endoplasmic Reticulum-Associated Protein Degradation Machinery in the Human Mast Cell Leukemia Cell Line HMC-1.2

The unfolded protein response is an intricate system of sensor proteins in the endoplasmic reticulum (ER) that recognizes misfolded proteins and transmits information via transcription factors to either regain proteostasis or, depending on the severity, to induce apoptosis. The main transmembrane sensor is IRE1α, which contains cytoplasmic kinase and RNase domains relevant for its activation and the mRNA splicing of the transcription factor XBP1. Mast cell leukemia (MCL) is a severe form of systemic mastocytosis. The inhibition of IRE1α in the MCL cell line HMC-1.2 has anti-proliferative and pro-apoptotic effects, motivating us to elucidate the IRE1α interactors/regulators in HMC-1.2 cells. Therefore, the TurboID proximity labeling technique combined with MS analysis was applied. Gene Ontology and pathway enrichment analyses revealed that the majority of the enriched proteins are involved in vesicle-mediated transport, protein stabilization, and ubiquitin-dependent ER-associated protein degradation pathways. In particular, the AAA ATPase VCP and the oncoprotein MTDH as IRE1α-interacting proteins caught our interest for further analyses. The pharmacological inhibition of VCP activity resulted in the increased stability of IRE1α and MTDH as well as the activation of IRE1α. The interaction of VCP with both IRE1α and MTDH was dependent on ubiquitination. Moreover, MTDH stability was reduced in IRE1α-knockout cells. Hence, pharmacological manipulation of IRE1α-MTDH-VCP complex(es) might enable the treatment of MCL.

Intracranial invasion of a mast cell tumour in a dog: A case report and review of the literature

An 11-year-old, female-neutered beagle was presented with a growing soft tissue mass arising within the deep tissues of the left cranial cervical region. At presentation, facial asymmetry was evident along with palpable lymphadenomegaly. Magnetic resonance imaging demonstrated a locally invasive cervical mass with intracranial invasion through focal osteolysis of the occipital bone. After antihistamine administration, cytology confirmed mast cell tumour (MCT) with metastasis to local lymph nodes and liver. The owner chose to pursue lomustine and prednisolone, which were dispensed, but, before home administration, prolonged seizures/status epilepticus occurred prompting euthanasia. Postmortem examination confirmed a high-grade MCT associated with, and infiltrating through, muscle, calvarium, dura mata, leptomeninges and the underlying brain. We present the clinical, imaging, and pathological findings of an unprecedented case of extracranial MCT tumour causing osteolysis of an imperforate flat bone (occipital bone) and intracranial invasion.

Mastocytosis in the skin in dogs: A multicentric case series

Canine cutaneous mastocytosis (CM) is rare in contrast to canine mast cell tumours. In humans, CM commonly affects children and is usually indolent with possible spontaneous resolution. Systemic mastocytosis (SM) with bone marrow involvement typically affects adults, can have a poor outcome, and often includes skin lesions. 'Mastocytosis in the skin' (MIS) is the preferred term of skin lesions, if bone marrow evaluations are not available, which is often the cases in dogs. In human SM and CM, KIT mutations are often detected. The veterinary literature suggests clinical resemblances between human and canine MIS, but data is limited, and KIT mutations are rarely assessed. This retrospective study describes clinicopathological findings, treatment and outcome of 11 dogs with suspected MIS. Dogs with multiple mast cell tumours were excluded. Histopathology reports (n = 5) or slides (n = 6) were reviewed. KIT mutation analysis including exons 8, 9, 11, 14 and 17 were analysed in eight dogs. Median age at diagnosis was 4 years (range, 1-12). Typical clinical signs included multifocal to generalised nodules and papules. Histologically, skin lesions were characterised by dermal infiltration of well-differentiated mast cells. KIT mutations were detected in 3/8 dogs (exon 9: n = 2; exon 11: n = 1). One dog had mastocytaemia suggesting possible SM. Glucocorticoids were mostly successful with lesion improvement in all treated dogs (n = 8). This cohort highlights resemblances between human and canine MIS. Further studies are required to confirm these findings and establish diagnostic criteria for CM and MIS associated with SM in dogs.

CT features of cutaneous and subcutaneous canine mast cell tumors and utility of conventional and indirect lymphography to detect clinically unknown mast cell tumors and to map the sentinel lymph nodes

Computed tomography is frequently used to stage canine mast cell tumors (MCTs). The aims of this prospective, observational study were to describe the CT features of MCTs, to evaluate the performance of CT in detecting additional or incidental MCTs, to distinguish between cutaneous (cMCT) or subcutaneous (scMCT) MCTs, and to identify one or multiple sentinel lymph nodes (SLNs) by indirect CT lymphography (ICTL). Seventy-two dogs affected by 111 MCTs were included. The recorded parameters were: shape, size, attenuation (Hounsfield units [HU]), location (cutaneous or subcutaneous), and presence of fat stranding. The SLNs were compared with the regional lymph nodes and supplementary MCTs were registered. Mast cell tumors mostly appeared with well-defined margins (89%), round/oval shape (71%), homogeneous enhancement (90%) with a mean postcontrast density of 62.0 ± 23.4 HU and associated with fat stranding (43%). Cutaneous mast cell tumors were more frequently round (P = .003), whereas scMCTs were oval (P = .011) with a larger mean maximal diameter (2.91 ± 1.57 cm vs 1.46 ± 1.28 cm, P = .002) and more feeding vessels (77% vs 39% P = .044). Compared with histopathology, CT accuracy in differentiating cMCTs and sMCTs was 57%, with an interobserver agreement of 88% (three reviewers). Indirect CT lymphography showed the SLN in 82 of 85 (97%) cases, 32% of them not corresponding to the regional node. CT showed additional or incidental MCTs in 23 of 72 (32%) dogs. In conclusion, the common CT appearance of canine cMCTs and scMCTs is reported with some statistical differences between the two categories. CT is useful in identifying clinically undetected MCTs and SLNs, although it shows low accuracy in distinguishing between cMCT and scMCT.

Cutaneous Canine Mast Cell Tumor: The Use of Proliferative Markers (Ki-67 and Ki-67 × AgNOR) in Cytological Samples for Diagnosis and Prognosis

A cytological grading system for canine mast cell tumors (MCTs) has been developed, but its integration into clinical routine has been hindered due to its diagnostic limitations. The aim of this study was to assess the prognostic value of Ki-67 and argyrophilic nucleolar organizing region (AgNOR) markers in cytological MCT samples and to determine cut-off values for these markers in correlation with histopathological grading. Cytological samples were collected prior to surgical excision, and histopathological samples were obtained postsurgery from 45 dogs diagnosed with cutaneous mast cell tumors (MCTs). The cytological specimens were classified using a two-tier grading system, and their Ki-67 (average immunopositive nuclei per 100 cells) and AgNOR (average AgNOR counts per 100 nuclei) signaling was assessed. Through receiver operating characteristic (ROC) analysis, cut-off values for Ki-67 and Ki-67 × AgNOR were determined to better align with histopathological grading (classified as low or high grade according to Kiupel's scoring system). Without the inclusion of proliferative markers, there was a 73% agreement between cytological and histopathological grading. The prediction of histopathological grade was slightly more accurate when assessing Ki-67 and Ki-67 × AgNOR signaling in cytological specimens (75% and 80%, respectively) compared to the initial cytological grading. The cytological assessment of canine MCTs proves beneficial for the initial evaluation, and the incorporation of the evaluation of Ki-67 and AgNOR markers may assist in identifying diagnostically highly malignant MCTs.

Sonographic and computed tomographic features of intestinal mast cell tumors mimicking alimentary lymphoma in 2 dogs

Two shih tzu dogs were referred to our clinic because of hematochezia and vomiting. Abdominal ultrasonography revealed a focal, asymmetric, exophytic small intestinal mass with loss of wall layering and muscular layer thickening of the adjacent intestine. Computed tomography (CT) in both dogs revealed a focal, asymmetric, homogenously contrast-enhanced exophytic jejunal and duodenal mass with an intact mucosal layer and generalized lymphadenopathy. Metastasis and ulceration were not detected on CT. The initial imaging diagnosis was lymphoma in both dogs; however, histopathological examination revealed the presence of intestinal mast cell tumors (iMCTs). Despite its similarity to alimentary lymphoma, iMCT should be considered a possible diagnosis, based on imaging characteristics, to ensure that proper treatments are selected. This is the first veterinary report describing detailed ultrasonographic and CT characteristics of iMCTs. Key clinical message: This is the first veterinary case report demonstrating sonographic and computed tomographic features of canine iMCT, which can be misdiagnosed as alimentary lymphoma. This report provides another differential diagnosis to consider when determining the appropriate patient treatment direction and histopathological examination.

Sentinel lymph node mapping in canine mast cell tumours using a preoperative radiographic indirect lymphography: Technique description and results in 138 cases

Several sentinel lymph node (SLN) mapping techniques, to detect nodal metastasis in canine tumours have been investigated in the last 10 years in veterinary oncology. The purpose of this prospective study was to describe a reliable, quick, and inexpensive technique for SLN mapping in canine patients affected by cutaneous and subcutaneous mast cell tumours (MCT). Eighty dogs were enrolled in this study for a total of 138 cytologically diagnosed MCTs. Sentinel lymph node mapping was performed by injecting iomeprole peritumorally followed by serial radiographs at 1, 3, 6 and 9-min post injection. A total of 168 SLNs were detected, 90% at first radiograph, 1 min after the peritumoral iomeprole injection, while in the rest of the cases SLN was identified at 3 min. Sentinel lymph nodes detected by the preoperative radiographic indirect lymphography with iomeprole (PRILI) differed from regional lymph nodes in 57% of cases. The PRILI technique detected simultaneously multiple SLNs in the 26% of cases and multiple lymph centers in the 31% of MCTs. To allow the surgical identification of the SLNs, a peritumoral injection of methylene blue was performed at the time of surgery. This study reports a widely available technique for SLN mapping using digital radiographs in combination with a water-soluble medium, representing a cost-effective alternative to other SLN mapping procedures. Based on our results, this technique can be effective for SLNs mapping in dogs with MCTs but further comparative studies are needed to assess its reliability and efficacy in different tumours.

Anal sac mast cell tumor in a dog

An 11-year-old castrated mixed-breed dog was diagnosed with a unilateral anal sac mass. Anal sacculectomy was performed without complication. Histopathology of the mass was consistent with a well-differentiated mast cell tumor. Analyses for the Ki-67 protein, KIT expression pattern, and the presence of c-kit mutations were done. Recovery from surgery was unremarkable and repeat staging revealed no evidence of mast cell disease at 4, 8, and 12 mo after surgery. To the authors' knowledge, primary mast cell neoplasia of the anal sac has not previously been reported in the veterinary literature. Key clinical message: Although mast cell tumors of the perineal region are commonly encountered in veterinary practice, the anal sac represents a novel location for this disease. Cytology of anal sac masses can be a useful diagnostic tool to confirm the diagnosis, guide staging, and assist in treatment decisions.

Lymphotropic nanoparticle magnetic resonance imaging for diagnosing metastatic lymph nodes in dogs with malignant head and neck tumours

Lymphotropic nanoparticle magnetic resonance imaging (LNMRI) utilises ultrasmall paramagnetic iron nanoparticles (USPIOs) for imaging of metastatic lymph nodes in patients afflicted with cancer. LNMRI has been shown to be a highly effective and accurate way to diagnose metastasis in humans but has not been commonly reported on in veterinary medicine. USPIOs are phagocytised by macrophages and then localised to lymph nodes where they create a susceptibility artefact on gradient echo MRI sequences. In this study dogs (n = 24) with naturally occurring head and neck tumours were imaged with LNMRI then had mandibular and retropharyngeal lymph nodes extirpated for histological analysis. Subjective and objective analysis of the LNMRI images was performed and imaging results compared to histology as the gold standard. A total of 149 lymph nodes were included in this study. The overall sensitivity, specificity and accuracy was 64%, 94.4% and 89.3% respectively. However, if dogs with mast cell tumours were excluded from analysis the sensitivity, specificity and accuracy rose to 85.7%, 95.7% and 94.6%. LNMRI is potentially an accurate way to determine the presence of lymph node metastasis in dogs with some types of head and neck tumours. However, LNMRI has only moderate accuracy in dogs with oral or mucocutaneous mast cell tumours in this region.

Case report: Resolution of malignant canine mast cell tumor using ketogenic metabolic therapy alone

Background

Mast cell tumors (MCT) are common neoplasms in dogs and are similar to most other malignant cancers in requiring glucose for growth, regardless of histological grade. Ketogenic metabolic therapy (KMT) is emerging as a non-toxic nutritional intervention for cancer management in animals and humans alike. We report the case of a 7 years-old Pit Bull terrier that presented in 2011 with a cutaneous mast cell tumor under the right nostril.

Methods

The patient’s parent refused standard of care (SOC) and steroid medication after initial tumor diagnosis due to the unacceptable adverse effects of these treatments. Following tumor diagnosis, the patient’s diet was switched from Ol’Roy dog food to raw vegetables with cooked fish. The tumor continued to grow on this diet until July, 2013 when the diet was switched to a carbohydrate free, raw calorie restricted ketogenic diet consisting mostly of chicken and oils. A dog food calculator was used to reduce calories to 60% (40% calorie restriction) of that consumed on the original diet. A total of 444 kilocalories were given twice/day at 12 h intervals with one medium-sized raw radish given as a treat between each meal.

Results

The tumor grew to about 3–4 cm and invaded surrounding tissues while the patient was on the raw vegetable, cooked fish diet. The tumor gradually disappeared over a period of several months when the patient was switched to the carbohydrate free calorie restricted ketogenic diet. The patient lost 2.5 kg during the course of the calorie restriction and maintained an attentive and active behavior. The patient passed away without pain on June 4, 2019 (age 15 years) from failure to thrive due to an enlarged heart with no evidence of mast cell tumor recurrence.

Conclusion

This is the first report of a malignant cutaneous mast cell tumor in a dog treated with KMT alone. The resolution of the tumor in this canine patient could have been due to the diet-induced energy stress and the restriction of glucose-driven aerobic fermentation that is essential for the growth of most malignant tumors. Further studies are needed to determine if this non-toxic dietary therapeutic strategy could be effective in managing other canine patients with malignant mast cell tumors.

Drug delivery targets and strategies to address mast cell diseases

INTRODUCTION

Current and developing mast cell therapeutics are reliant on small molecule drugs and biologics, but few are truly selective for mast cells. Most have cellular and disease-specific limitations that require innovation to overcome longstanding challenges to selectively targeting and modulating mast cell behavior. This review is designed to serve as a frame of reference for new approaches that utilize nanotechnology or combine different drugs to increase mast cell selectivity and therapeutic efficacy.

AREAS COVERED

Mast cell diseases include allergy and related conditions as well as malignancies. Here, we discuss the targets of existing and developing therapies used to treat these disease pathologies, classifying them into cell surface, intracellular, and extracellular categories. For each target discussed, we discuss drugs that are either the current standard of care, under development, or have indications for potential use. Finally, we discuss how novel technologies and tools can be used to take existing therapeutics to a new level of selectivity and potency against mast cells.

EXPERT OPINION

There are many broadly and very few selectively targeted therapeutics for mast cells in allergy and malignant disease. Combining existing targeting strategies with technology like nanoparticles will provide novel platforms to treat mast cell disease more selectively.

Case of mastocytemia and systemic mastocytosis in a dog: ProCyte Dx and Sysmex XT-2000i scattergram findings, morphologic features, and c-kit somatic mutation analysis

A 10-year-old female Golden Retriever was presented for a recheck after the complete removal of low-grade complex mammary carcinoma. The in-house ProCyte Dx automated counts revealed moderate regenerative anemia and moderate eosinophilia. The ProCyte Dx WBC scattergram showed a cloud in an unusual place parallel and to the right of the monocyte dot plot location. Cells were classified as either monocytes or neutrophils with no clear separation. Complete blood count analysis performed in the laboratory on a Sysmex XT-2000iV analyzer showed moderate regenerative anemia and WBC count within RI; a differential count was not provided by the instrument. On the Sysmex XT-2000iV DIFF scattergram, neutrophil and eosinophil dot plots were present at the respective locations and appeared separated, but the instrument did not provide numerical results. In addition to the normal lymphocyte dot plot location, the second cloud of cells classified as lymphocytes was displayed to the right of the monocyte dot plot area. On the WBC/BASO scattergram, the second population of cells was present above and to the right of the leukocyte cluster. Morphologic assessment of the blood smear detected mastocytemia with 16% poorly granulated and degranulated mast cells. FNAs from the liver and spleen contained large aggregates of poorly granulated mast cells. C-kit somatic mutation screening detected the presence of point mutation S479I in exon 9 of the canine c-KIT gene. This is the first description of abnormal scattergrams from ProCyte Dx and Sysmex XT-2000iV analyzers in a dog with concurrent mastocytemia and systemic mastocytosis, and where cytologic assessments of a blood smear, liver, and spleen, and c-kit somatic mutation analysis were performed.

Treatment of multiple synchronous canine mast cell tumours using intratumoural tigilanol tiglate

Mast cell tumours (MCTs) are common canine skin neoplasia. While they generally occur as single tumours, multiple synchronous MCTs (msMCTs) of de novo/non-metastatic origin are reported in a proportion of the patient population. Where there is no evidence of metastasis or lymphatic spread, MCTs are effectively controlled by surgery and other local therapies. However, treatment of de novo msMCTs can be more challenging, especially when they occur in surgically difficult locations. Here, we report the use of tigilanol tiglate, a novel small molecule registered as a veterinary pharmaceutical for the local treatment of non-metastatic MCTs, in the treatment of patients with msMCTs presenting at three Australian specialist referral centres. We also present a meta-analysis of the literature to provide a better understanding of the prevalence of canine msMCTs. Notably, nine patients with a total of 32 MCTs were treated during the study. A complete response was recorded in 26 (81%) of the individual MCTs on Day 28 after a single tigilanol tiglate injection. Of the 6 initially non-responsive MCTs, one achieved a complete response after a further tigilanol tiglate treatment. A complete response was reported at 6 months in all 22 of the tumours that were evaluable and that had recorded a complete response at Day 84. For the literature meta-analysis, 22 studies were found with prevalence estimates of msMCTs ranging from 3 to 40%; when combined, these studies yielded 3,745 patients with a prevalence of 13% (95% CI 10; 16). Overall, the results demonstrate the utility of intratumoural tigilanol tiglate as an option for the treatment of multiple MCTs where multiple surgical resections would have been required.

Vet-OncoNet: Malignancy Analysis of Neoplasms in Dogs and Cats

Simple Summary

An overview analysis of tumors in dogs and cats, dividing them into malignant and benign, may provide previously unknown information about the biological behavior of tumors in these species and may serve many veterinarians as a support for clinical decision making. Based on a sample of 16,272 cancer records, including 3266 cats and 13,006 dogs, the analysis found that cats have a fourfold risk of malignant tumors, as in some topographies. Sex appears to play a role in the malignancy only in dogs. Some dog breeds (Pit bull and Boxer) have a higher risk of malignant tumors as opposed to Shih tzu and Yorkshire terrier. District of residence was not relevant in predicting malignancy risk. Most importantly, the risk of malignant tumors increases by 20% every three years.

Abstract

Analysis of canine and feline tumor malignancy data can help clinicians identify high-risk patients and make more accurate decisions. Based on a sample of 16,272 cancer records, including 3266 cats and 13,006 dogs, collected from January 2019 to December 2021 in the Vet-OncoNet Network database, this study aimed to compare the tumor malignancy profile between cats and dogs, considering animal-related factors (sex, age, and breed), topography, and geographic location using a mixed-effects logistic regression model. Cats had a higher proportion of malignant tumors (78.7%) than dogs (46.2%), and the malignancy profile was very different regarding tumors’ topographies. The mean age of malignant tumors occurred eight months later than benign ones (9.1, SD = 3.4; 9.8, SD = 3.2), in general. Species (OR = 3.96, 95%CI 3.57: 4.39) and topography (MOR = 4.10) were the two most important determinants of malignancy risk. Female dogs had a higher risk than male dogs (OR = 1.19, 95%CI 1.08: 1.31), which does not appear to be the case in cats (OR = 0.98, 95%CI 0.77: 1.23). Breed contributed significantly to differences in malignancy risk in dogs (MOR = 1.56), particularly in pit bulls and boxers. District of residence was not so relevant in predicting malignancy risk (MOR = 1.14). In both species, the risk of malignancy increased by approximately 20% every three years. It could be hypothesized that species differences in genetic structure may contribute to tumor malignancy.

Sentinel Lymph Node Mapping with Indirect Lymphangiography for Canine Mast Cell Tumour

Simple Summary

Mast cell tumour (MCT) is a common cutaneous and subcutaneous neoplasia in dogs. Recent studies describe that sentinel lymph node (SLN) assessment is more specific to stage MCT, while regional lymph node (RLN) evaluation is not as specific. SNL is the first site of drainage of a tumour and the first metastatic site in several tumours. The study aims to evaluate the SLN drainage mapping of MCT with indirect lymphography in dogs. The second objective of the study is to compare the SLN to the RLN. Survey radiographs followed by an indirect lymphography were obtained for SLN mapping. Twenty-six dogs with 29 MCTs were included. SLNs were detectable in 26 MCTs and radiographic indirect lymphangiography with Lipiodol was able to detect at least one SLN in 90% of MCTs in dogs. In conclusion, radiographic indirect lymphangiography with Lipiodol is a feasible technique to map SLNs and its draining system in MCTs. The lymph drainage pattern of the MCTs may be different for each MCT and more than one SLN can be involved.

Abstract

Mast cell tumour (MCT) is a common cutaneous and subcutaneous neoplasia in dogs. It can metastasise to lymph nodes (LNs), and this adversely affects the prognosis and treatment. The study aims to evaluate the SLN mapping of MCTs with radiographic indirect lymphography. Dogs that underwent clinical staging were prospectively enrolled. Lipiodol was injected around the MCT or the surgical scar. After 24 h, LNs that picked up contrast were radiographically assessed. Twenty-six dogs with 29 MCTs were included. MCTs were confirmed histologically, while SLNs were evaluated either by cytology and/or histology. SLNs were detectable in 23 dogs with 26 MCTs. Lymphatic vessels were visible in 19 MCTs. In nine MCTs, at least two SLNs picked up contrast. In particular, seven MCTs involved two SLNs, and two MCTs involved three different SLNs. In nine MCTs, at least a SLN was metastatic. This study indicates that the lymph drainage pattern of the MCTs may be different for each MCT, and more than one SLN can be involved. Indirect lymphangiography with Lipiodol allowed the detection of the SLN in 90% of MCTs. This provided clinically relevant information to remove the LN and stage the patient.

The Role of Fine Needle Aspiration of Liver and Spleen in the Staging of Low-Grade Canine Cutaneous Mast Cell Tumor

Clinical staging is a fundamental step in the clinical assessment of canine cutaneous mast cell tumor (cMCT), and it is recommended to evaluate the tumor draining lymph node (eTDLN), perform diagnostic imaging, and fine needle aspiration (FNA) of the spleen and liver to determine the presence of metastatic disease, thereby refining the prognosis. The aim of this retrospective study was to evaluate the prevalence of splenic and hepatic involvement in newly diagnosed canine low-grade cMCT (Patnaik grade I–II, Kiupel low-grade). Medical records of dogs that underwent a clinical staging work-up and surgical excision for a low-grade cMCT between December 2019 and December 2021 were reviewed at five veterinary centers. Only dogs with a histological diagnosis of low-grade cMCT, FNA or histology of the eTDLN, FNA of the spleen and liver, and one year of follow up were included. One hundred and thirty-six dogs met the inclusion criteria. Only 1 out of 136 dogs (0.7%) had the presence of visceral metastases at diagnosis, suggesting that the prevalence of visceral metastases in low-grade cMCT is extremely low. The results of this study are consistent with previous literature and suggest that after a diagnosis of low-grade cMCT, cytology of visceral organs may not represent an essential step in the clinical staging work-up.

Reproducibility and Feasibility of Classification and National Guidelines for Histological Diagnosis of Canine Mammary Gland Tumours: A Multi-Institutional Ring Study

Simple Summary

Tumours of the mammary gland are common in humans, as in canine species. They are very heterogenous with numerous morphological variants and different biologic behaviours. In the last few decades, several efforts have been made to classify these tumours histologically and establish the level of malignancy by using histologic grading systems. However, reproducibility and diagnostic agreement of such classification and grading have been only rarely assessed. In this study, we tested the variability in diagnoses performed by 15 pathologists using the same classification and grading system. Prior to the study, pathologists agreed on guidelines regarding how to apply these systems. Pathologists worked blindly on 36 digital histologic slides of canine mammary tumours. The agreement was statistically analysed using Cohen’s kappa coefficient that, when equal to 1, indicates perfect agreement. The overall agreement in the identification of hyperplastic-dysplastic/benign/malignant lesions was substantial (kappa 0.76), while outcomes on morphological classification had only a moderate agreement (k = 0.54). Tumour grade assigned by pathologists was the least concordant and kappa could not be calculated. Although promising, the results underline that each diagnostic/grading system should be assessed and optimized for standardization and high diagnostic agreement.

Abstract

Histological diagnosis of Canine Mammary Tumours (CMTs) provides the basis for proper treatment and follow-up. Nowadays, its accuracy is poorly understood and variable interpretation of histological criteria leads to a lack of standardisation and impossibility to compare studies. This study aimed to quantify the reproducibility of histological diagnosis and grading in CMTs. A blinded ring test on 36 CMTs was performed by 15 veterinary pathologists with different levels of education, after discussion of critical points on the Davis-Thompson Foundation Classification and providing consensus guidelines. Kappa statistics were used to compare the interobserver variability. The overall concordance rate of diagnostic interpretations of WP on identification of hyperplasia-dysplasia/benign/malignant lesions showed a substantial agreement (average k ranging from 0.66 to 0.82, with a k-combined of 0.76). Instead, outcomes on ICD-O-3.2 morphological code /diagnosis of histotype had only a moderate agreement (average k ranging from 0.44 and 0.64, with a k-combined of 0.54). The results demonstrated that standardised classification and consensus guidelines can produce moderate to substantial agreement; however, further efforts are needed to increase this agreement in distinguishing benign versus malignant lesions and in histological grading.

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.

Imatinib Mesylate for the Treatment of Canine Mast Cell Tumors: Assessment of the Response and Adverse Events in Comparison with the Conventional Therapy with Vinblastine and Prednisone

Mast cell tumors (MCTs) are common neoplasms in dogs, and treatments for these diseases include surgery, polychemotherapy and targeted therapy with tyrosine kinase inhibitors. This study aimed to evaluate the response and the adverse events of treatment with imatinib mesylate (IM) compared to conventional therapy using vinblastine and prednisolone (VP) in canine cutaneous MCTs. Twenty-four dogs were included in the study; 13 animals were treated with IM and 11 with VP. Tumor tissue samples were submitted for histological diagnosis, grading and KIT immunostaining. The response to treatment was assessed by tomographic measurements according to VCOG criteria. Adverse events were classified according to VCOG-CTCAE criteria. The IM and VP groups had dogs with similar breeds, gender, ages, MCT localization, WHO stages and lymph node metastasis profiles. Most MCTs were grade 2/low and had KIT- patterns 2 and 3. The objective response rate (ORR) was significantly higher (30.79%) in the IM group then in VP group (9.09%). Adverse events (AE) in IM group were all grade 1, significantly different from VP. In conclusion, IM presented better ORR and less severe adverse events when compared to VP, representing a suitable option for the treatment of low-grade canine MCTs.