Proposal of a 2-tier histologic grading system for canine cutaneous mast cell tumors to more accurately predict biological behavior

Tibial Plateau and Stifle Joint Invasion with a Subcutaneous Mast Cell Tumor

A 4 yr old female neutered Labrador retriever was referred with a history of left hind-limb lameness and an acute, nonpainful, subcutaneous mass on the medial aspect of the left stifle. Stifle radiographs and fine needle aspirates of the soft tissue mass performed by the referring veterinarian confirmed the presence of predominantly highly granulated mast cells, consistent with a mast cell tumor. Computed tomography demonstrated a soft tissue mass centered on the left medial stifle, with associated joint effusion and polyostotic lytic lesions on the tibial plateau and distal patella. Ultrasound-guided aspirates of the liver, spleen, and popliteal lymph nodes were obtained to rule out further metastatic spread. Cytology of the joint fluid demonstrated a low number of well-differentiated mast cells. Surgical and oncological interventions were discussed, and full hind-limb amputation was elected. Histopathological analysis of the submitted tissues after amputation diagnosed a subcutaneous mast cell tumor with neoplastic cell infiltrate extending into sections of joint capsule and synovial membrane. Infiltration to the tibia and distal patella were suspected following the presence of mast cell clusters in both osteolytic lesions. No evidence of metastasis was identified in the popliteal lymph node. Postoperative monitoring of iliac lymph node size using ultrasound did not identify evidence of metastasis 12 mo postoperatively.

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.

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.

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.

Retrospective analysis of outcome and prognostic factors of subcutaneous mast cell tumours in dogs undergoing surgery with or without adjuvant treatment

Subcutaneous mast cell tumours (SC MCTs) can display a different biological behaviour in dogs when compared to their cutaneous counterpart. There is a paucity of information with regards to the outcome of dogs with SC MCTs treated with surgery and/or receiving adjuvant chemotherapy. The aim of this study was to retrospectively review the outcome of dogs with surgically excised SC MCTs undergoing adjuvant treatment or not. A secondary aim was to assess prognostic factors in the same group. Fifty-two cases were included. Recurrence rate was 15% and 63% of evaluated lymph nodes were consistent with early or overt metastasis. Median survival time (range 83-1357 days) and median time to progression (range 14-1357 days) were not reached. Factors predictive of shorter overall survival time included increasing age (HR 1.29, 95% CI 1.06-1.55, p = .0092), presence of clinical signs at presentation (HR 10.44, 95% CI 2.69-40.52, p = .0007), mitotic count >4 (HR 8.69, 95% CI 2.55-29.55, p = 0.0005), presence of multinucleation (HR 4.21, 95% CI 1.35-13.18, p = .0135), use of neoadjuvant and adjuvant chemotherapy (HR 7.16, 95% CI 1.26-40.73, p = .0266). The same factors, together with increasing tumour dimensions, were predictive for shorter progression-free survival (PFS), including increasing age (p = .0012), presence of clinical signs at presentation (p = .0045), increasing tumour dimensions (p = .0004), MC > 4 (p = .0004), presence of multinucleation (p = .0282), use of neoadjuvant and adjuvant chemotherapy (p = .0485). No variables remained significant for overall survival using multivariate analysis. There was a longer survival in cases where chemotherapy was not required (HR 0.14, 95% CI 0.03-0.68, p = .0148), and this variable remained significant for PFS on multivariate analysis (HR 0.13, 95% CI 0.02-0.76, p = .02). In conclusion, our study suggests that dogs with SC MCTs, in the absence of negative prognostic factors, may have a prolonged survival when treated with surgery alone. Further studies are needed to clarify the role of adjuvant treatment for biologically aggressive SC MCTs in dogs.

A comprehensive multi-domain dataset for mitotic figure detection

The prognostic value of mitotic figures in tumor tissue is well-established for many tumor types and automating this task is of high research interest. However, especially deep learning-based methods face performance deterioration in the presence of domain shifts, which may arise from different tumor types, slide preparation and digitization devices. We introduce the MIDOG++ dataset, an extension of the MIDOG 2021 and 2022 challenge datasets. We provide region of interest images from 503 histological specimens of seven different tumor types with variable morphology with in total labels for 11,937 mitotic figures: breast carcinoma, lung carcinoma, lymphosarcoma, neuroendocrine tumor, cutaneous mast cell tumor, cutaneous melanoma, and (sub)cutaneous soft tissue sarcoma. The specimens were processed in several laboratories utilizing diverse scanners. We evaluated the extent of the domain shift by using state-of-the-art approaches, observing notable differences in single-domain training. In a leave-one-domain-out setting, generalizability improved considerably. This mitotic figure dataset is the first that incorporates a wide domain shift based on different tumor types, laboratories, whole slide image scanners, and species.

Ki67 Index in Patnaik Grade 2/Kiupel Low-Grade Canine Cutaneous Mast Cell Tumors with Early Lymph Node Metastasis: A Descriptive Study

Several studies evaluating Ki67 in canine cutaneous mast cell tumors (cMCTs) have reported its prognostic value when tumors of all histological grades are included. This study aims to evaluate whether the Ki67 index has a predictive value in a homogeneous cohort of G2/LG cMCTs with HN2 lymph nodes (LNs) and to describe the clinical outcome. The second goal was to explore the correlation between the Ki67 index and MC. The medical databases of three institutions were retrospectively searched for dogs undergoing surgical treatment for cMCT and LN extirpation, with a histological diagnosis of G2/LG with HN2 LNs. Information about histological margins, MC, Ki67 index, local recurrence, nodal relapse, distant metastasis, de novo cMCT occurrence and date and cause of death were included. A total of 39 cases were identified. None of these developed local and nodal relapse or metastatic distant disease. Median MC was 1 (0-2). Median Ki67 index was 3.5 (0.7-14.3). Ki67 and MC were not significantly correlated. At the end of the study, 32 (82%) dogs were alive, 7 (18%) dogs were dead from unrelated causes and 4 (10.2%) dogs were lost to follow-up. The median ST was not reached, and the mean was 893 days (104-2241 days). Considering the strict inclusion criteria, dogs affected by G2/LG with HN2 LNs treated with surgery alone may have a good oncologic outcome; the Ki67 index does not have prognostic impact.

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.

Tyrosine kinase inhibitors as an alternative treatment in canine mast cell tumor

The current gold standard treatment for canine mast cell tumors (MCT) uses vinblastine sulfate (VBL) as chemotherapy, although tyrosine kinase inhibitors (TKI) have recently been shown to be worthy candidates for treatment. This systematic review aimed to analyze the overall survival (OS), progression-free survival (PFS), overall response rate (ORR), and complete (CR) or partial response (PR) in dogs with MCT treated with TKI compared to standard VBL treatment. The systematic review was registered in the Open Science Framework (OSF) database under the identifier 10.17605/OSF.IO/WYPN4 (https://osf.io/). An electronic search was performed in nine databases. References from eligible studies were also selected to find more registers. A total of 28 studies met the eligibility criteria, and one more was recovered from the references of eligible studies, totaling 29 selected studies. The overall response rate, complete response, and partial response were higher in dogs treated with tyrosine kinase inhibitors than in dogs treated with vinblastine. The overall survival and progression-free survival of vinblastine-treated dogs were higher compared to tyrosine kinase inhibitors-treated dogs. Dogs with mutated KIT treated with tyrosine kinase inhibitors have longer overall survival and progression-free survival compared to those treated with vinblastine. It is important to consider the limitation of the study which should temper the interpretation of the results, videlicet, the extracted data lacked sample standardization and included variables such as animal characteristics, mutation detection methods, tumor characteristics, and treatment types which may have influenced the outcome of the study.

Systematic review registration

https://osf.io/, identifier: 10.17605/OSF.IO/WYPN4.

Clinical Implications of Immune Checkpoints and the RANK/RANK-L Signaling Pathway in High-Grade Canine Mast Cell Tumors

Mast cell tumors (MCTs) are the most common malignant cutaneous tumors in dogs, and they present extremely variable biological behavior. The interaction between RANK, RANK-L, and immune checkpoints is frequently detected in the tumor microenvironment, and, together, they participate in every stage of cancer development. Thus, the aim of this study was to characterize the molecular profiles of PD-L1, CTLA-4, RANK/RANK-L signaling pathway, and IFN-γ in primary tumors and lymph node metastases. Formalin-fixed, paraffin-embedded slides of MCTs and metastatic lymph nodes of ten dogs were submitted to immunohistochemical investigations. The results demonstrated that the tumor microenvironment of the high-grade mast cell tumors showed moderate or intense immunolabeling of all proteins, and the lymph node metastases also showed moderate or intense immunolabeling of checkpoint proteins. In addition, MCTs larger than 3 cm were associated with intensified PD-L1 (p = 0.03) in metastatic lymph nodes and RANK-L (p = 0.049) immunoreactivity in the tumor. Furthermore, dogs with a survival time of less than 6 months showed higher PD-L1 immunoreactivity (p = 0.042). In conclusion, high-grade MCT is associated with an immunosuppressive microenvironment that exhibits elevated RANK/RANK-L signaling and enhanced immune checkpoint immunoreactivity, potentially facilitating intratumorally immune escape. These biomarkers show promise as clinical indicators of disease progression and might response to immunotherapy in dogs with high-grade MCTs, thus emphasizing their importance for guiding treatment decisions and improving outcomes.

Evaluation of Surgical Aid of Methylene Blue in Addition to Intraoperative Gamma Probe for Sentinel Lymph Node Extirpation in 116 Canine Mast Cell Tumors (2017-2022)

Methylene Blue (MB) is combined with radiopharmaceutical for intraoperative sentinel lymph node (SLN) mapping, but its role during SLN extirpation has not been investigated yet in veterinary medicine. The aim of this study was to assess whether MB increased surgical detection of SLN beyond the use of intraoperative gamma-probe (IGP) alone in clinically node-negative dogs with mast cell tumors (MCTs) following the detection of sentinel lymphocentrums (SLCs) via preoperative planar lymphoscintigraphy. Dogs enrolled underwent MCT excision and SLC exploration guided by both MB and IGP. Data recorded for each SLN were staining (blue/non-blue), radioactivity (hot/non-hot), and histopathological status (HN0-1 vs. HN2-3). A total of 103 dogs bearing 80 cutaneous, 35 subcutaneous, and 1 mucocutaneous MCTs were included; 140 SLCs were explored, for a total of 196 SLNs removed. Associating MB with IGP raised the SLNs detection rate from 90% to 95%. A total of 44% of SLNs were metastatic: 86% were blue/hot, 7% were only blue, 5% were only hot, and 2% were non-blue/non-hot. All HN3 SLNs were hot. Combining MB with IGP can increase the rate of SLN detection in dogs with MCTs; nonetheless, all lymph nodes identified during dissection should be removed, as they might be unstained but metastatic.

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.

Comparison of indirect computed tomographic lymphography and near-infrared fluorescence sentinel lymph node mapping for integumentary canine mast cell tumors

OBJECTIVE

To compare the independent and combined use of indirect computed tomographic lymphography (ICTL) and near-infrared fluorescence (NIRF) for sentinel lymph node (SLN) mapping in dogs with integumentary mast cell tumors (MCT) and report the metastatic LN rate.

STUDY DESIGN

Prospective clinical study.

ANIMALS

Twenty client-owned dogs.

METHODS

Dogs underwent preoperative ICTL, then intraoperative NIRF SLN mapping and excision of the anatomic lymph node (ALN) and/or SLN, and primary MCT. Technique agreement was complete if the same SLN was detected, and partial if the same SLN was detected along with additional SLN. No agreement occurred if the techniques detected different or no SLN. MCT were graded using two- and three-tier schemes, and LN were graded from HN0-3; HN2-3 were considered metastatic.

RESULTS

Complete, partial, and no agreement between ICTL and NIRF was seen in 8/20 (40%), 8/20 (40%), and 4/20 (20%) dogs, respectively. Detection of ICTL-SLN and NIRF-SLN failed in 1/20 (5%) and 4/20 (20%), respectively. Tumors were grade II/low-grade in 19/20 (95%) and grade III/high-grade in 1/20 (5%) dogs. Nineteen out of 20 (95%) dogs had HN2-3 LN.

CONCLUSIONS

Technique agreement of at least one SLN was seen in 16/20 (80%) dogs. Although most MCT were classified as intermediate to low grade, LN metastases were commonly detected.

CLINICAL SIGNIFICANCE

Combining ICTL and NIRF for MCT SLN mapping yields high SLN detection rates. Lymph node metastasis may be more common than previously reported for intermediate to low grade MCT.

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.

Patterns of nodal metastases, biological behaviour and prognosis of canine mast cell tumours of the pinna: A multi-institutional retrospective study

Canine cutaneous mast cell tumours (cMCTs) of the pinna have been associated with an aggressive biological behaviour, although data remain scarce. The knowledge acquired over the past years on histologic gradings, and the value of lymph node (LN) staging, may help in better characterizing this anatomical presentation. The first aim was to describe the frequency, location, and histologic appearance of LN metastases in cMCT of the pinna. A second aim was to evaluate prognosis. Medical records of dogs with cMCT of the pinna, that underwent tumour and sentinel (SLN) or regional LN (RLN) excision, were reviewed. The influence of potential prognostic variables on time to progression (TTP) and tumour-specific survival (TSS) was investigated. Thirty-nine dogs were included: 19 (48.7%) had Kiupel high-grade (K-HG) and 20 (51.3%) had low-grade (K-LG) MCTs. Eighteen (46.1%) dogs underwent SLN mapping: the superficial cervical LN was at least one of SLN in 17 (94.4%) cases. Twenty-two (56.4%) dogs had LN metastases; the superficial cervical LN was always involved. On multivariable analysis, only K-HG was associated with increased risk of progression (p = .043) and tumour-related death (p = .021). Median TTP and TSS were 270 and 370 days in K-HG, respectively; these were not reached in dogs with K-LG tumours (p < .01). cMCTs of the pinna are often K-HG and are also associated with a higher frequency of LN metastasis; however, we confirmed the independent prognostic value of histologic grading. A multimodal treatment may lead to favourable long-term outcome. Moreover, the superficial cervical LN is most often the SLN.

Validation of p53 Immunohistochemistry (PAb240 Clone) in Canine Tumors with Next-Generation Sequencing (NGS) Analysis

In human medicine, p53 immunohistochemistry (IHC) is a common method that is used for the identification of tumors with TP53 mutations. In veterinary medicine, several studies have performed IHC for p53 in canine tumors, but it is not known how well it actually predicts the mutation. The aim of this study was to estimate the accuracy of the IHC method for p53 (clone PAb240) using a lab-developed NGS panel to analyze TP53 mutations in a subset of malignant tumors in dogs. A total of 176 tumors were analyzed with IHC and then 41 were subjected to NGS analysis; among them, 15 were IHC positive and 26 were negative, and 16 out of 41 (39%) were found to be inadequate for NGS analysis. Excluding the non-evaluable cases at NGS, of the remaining eight IHC-positive cases, six were mutants and two were wild-type. Among the 17 IHC-negative cases, 13 were wild type, and 4 were mutants. The sensitivity was 60%, specificity was 86.7%, and the accuracy was 76%. These results suggest that when using IHC for p53 with this specific antibody to predict mutation, up to 25% wrong predictions can be expected.

Indirect lymphography for sentinel lymph node detection in dogs with mast cell tumors

Objective

The objective of this report is to describe the technique and diagnostic utility of indirect lymphography (IL) using water-soluble contrast for sentinel lymph node (SLN) mapping in dogs with mast cell tumors.

Animals

Fifty-three dogs with 59 mast cell tumors were included.

Procedure

Medical records were retrieved for dogs with a cytological diagnosis of mast cell tumor which also had IL performed for lymph node mapping. Dogs were excluded when surgery had been performed before presentation. Images were reviewed by a Board-certified radiologist for uptake of contrast within the sentinel lymph node.

Results

Lymphography studies from 34 tumors (57.6%) were diagnostic (clearly identifiable lymphatics and sentinel lymph node). Lymphography studies from 12 tumors (20.3%) were partially diagnostic (identifiable lymphatics, but sentinel lymph node not highlighted). Lymphography studies from 13 tumors (22%) were non-diagnostic. Indirect lymphography studies were interpreted as either diagnostic or partially diagnostic in 77.9% of tumors.

Conclusion

The results indicate that IL is a simple, available technique to allow for identification of a sentinel lymph node in dogs with mast cell tumors.

Clinical relevance

Indirect lymphography is a simple and widely accessible technique for SLN mapping in dogs with mast cell tumors, particularly for the general practice environment.

Preliminary Assessment of Tumor-Associated Tissue Eosinophilia (TATE) in Canine Mast Cell Tumors: Prevalence and Prognostic Relevance and Its Association with Neoangiogenesis

Mast cell tumor (MCT) is the most common malignant skin tumor in dogs. In order to gain more information on the prognostic markers in MCT, the role of the eosinophil granulocytes infiltrates was investigated and assessed by the evaluation of tumor-associated tissue eosinophilia (TATE) in 87 canine cutaneous MCTs. In human medicine, high TATE are often described in highly angiogenic tumors: we therefore assessed the vascular endothelial growth factor (VEGF) expression in neoplastic mast cells. TATE and VEGF expression were compared between themselves, with histological grading, immunohistochemical expression of KIT and Ki-67, and with the recurrence. We found a statistically significant correlation between TATE and Patnaik grading (p = 0.041), Kiupel grading (p = 0.022), immunohistochemical KIT expression (p = 0.015), and tumor recurrence (p = 0.000). No associations were observed with Ki-67 and VEGF expression. This is the first evaluation of TATE and its prognostic value in canine MCTs in veterinary oncology. This study suggest that this investigation could be an important source of information for this tumor and for other neoplasms.

Sentinel lymph node mapping with computed tomography lymphography for mast cell tumours and a comparison between regional and sentinel lymph node histological status: Sixty-two cases

It is known that the regional lymph node (RLN) may not correspond to the sentinel lymph node (SLN) (the first lymph node draining the tumour), and many diagnostic techniques have recently been aimed at its detection. Although lymphoscintigraphy is the gold standard in both human and veterinary medicine for SLN mapping, it is relatively unavailable in veterinary medicine due to costs and difficult management of the radiotracer. This prospective study evaluated, as a first aim, the feasibility and sensitivity of the computed tomography lymphography (CTL) in detecting the SLN in 62 mast cell tumours (MCTs). The second aim was to evaluate the accuracy of the CTL in identifying the most representative lymph node of the patient's lymphatic status; the histological status of the SNL was compared with that of the RLN, to see in how many cases the patient's stage would have changed according to the RLN. When the RLN turned out to be also the SLN it was decided to excise, as a control LN, the one localised in the neighbourhood of the MCT (neighbouring lymph node; NLN). The detection rate was 90%, with failure of SLN identification in six cases. In 18 (32%) of 56 MCTs with a diagnostic CTL, the SLN did not correspond to the RLN. Forty-five MCTs were surgically removed, together with their corresponding SLN and RLN/NLN. Since the clinical stage of the patient would have changed in only 7% of cases, CTL is a reliable method of detecting the SLN and, for staging purposes, there is no need to remove other LNs.

Plasma small extracellular vesicles from dogs affected by cutaneous mast cell tumors deliver high levels of miR-21-5p

Small extracellular vesicles (sEV) are a class of extracellular vesicles (30-150 nm), delivering molecules including proteins, metabolites, and microRNAs (miRNAs), involved in physiological intercellular crosstalk and disease pathogenesis. The present pilot study aims are (I) to develop an easy and fast protocol for the isolation of sEV from plasma of mast cell tumor (MCT)-affected dogs; (II) to evaluate if miR-21-5p (sEV-miR-21-5p), a miRNA overexpressed by MCT, is associated with sEV. Seventeen dogs have been enrolled in the study: 4 healthy and 13 (6 with and 7 without nodal metastasis) MCT-affected dogs. sEV were isolated using size exclusion chromatography (SEC) (IZON column 35nm) and were characterized by Western blot, Nanoparticle tracking analysis, and transmission electron microscopy. sEV-miR-21-5p was quantified using digital PCR. sEV expressed the specific markers CD9 and TSG101, and a marker of mast cell tryptase. The sEV mean concentration and size were 2.68E + 10 particles/ml, and 99.6 nm, 2.89E + 10 particles/ml and 101.7 nm, and 3.21E + 10 particles/ml and 124 nm in non-metastatic, nodal metastatic, and healthy samples, respectively. The comparative analysis demonstrated that the level of sEV-miR-21-5p was significantly higher in dogs with nodal metastasis compared to healthy (P = 0.038) and without nodal metastasis samples (P = 0.007). In conclusion, the present work demonstrated that a pure population of sEV can be isolated from the plasma of MCT-affected dogs using the SEC approach and that the level of sEV-miR-21-5p is higher in nodal metastatic MCT-affected dogs compared with healthy and MCT-affected dogs without nodal involvement.

Salivary miR-21 is a potential biomarker for canine mast cell tumors

MicroRNAs (miRNAs) are a class of noncoding RNA molecules playing a crucial role in tumor modulation targeting mRNA. This study aimed to validate the diagnostic potential of a panel of 3 miRNAs previously identified in canine mast cell tumors (MCTs), miR-21, miR-379, and miR-885, as markers of lymph node involvement in terms of histological absence (nonmetastatic: HN0; premetastatic: HN1) and presence (early-metastatic: HN2; overt-metastatic: HN3) of metastasis, in the saliva of mast cell tumor (MCT)-affected dogs by quantitative polymerase chain reaction (PCR). Forty-seven saliva samples were analyzed: 36 from MCT-affected dogs (12 subcutaneous [3 HN0-1 and 9 HN2-3] and 24 cutaneous [9 HN0-1 and 15 HN2-3-MCT]) and 11 from healthy dogs. MCT-group effects were investigated using analysis of variance (ANOVA). The origin of the tumor affected the expression of salivary miR-21 (P = .011) with an increase in cases with subcutaneous MCTs compared with the healthy group (P = .0005) and those with cutaneous MCTs (P = .004). Salivary miR-21 was higher in the HN2-3 class compared with the healthy group (P = .004). Salivary miR-885 was not affected by the presence of MCT, while miR-379 was not detected in saliva. The diagnostic potential of salivary miR-21 in discriminating MCT-affected dogs from the healthy group (AUC = 0.8917), cutaneous from subcutaneous (AUC = 0.8111), and subcutaneous HN0-1 (AUC = 0.7250) and HN2-3 (AUC = 0.9750) classes from healthy samples was demonstrated by receiver operating characteristic curve analysis. Overall, salivary miR-21 was identified as a promising tool, representing a novel approach to detecting MCT-associated epigenetic alterations in a minimally invasive manner.

Scar revision for incompletely or narrowly excised cutaneous mast cell tumors in dogs

Objective

Describe clinical features and outcomes of dogs undergoing scar revision for incompletely or narrowly excised cutaneous mast cell tumors without gross disease.

Animals

52 dogs undergoing 54 scar revisions.

Procedures

Retrospective record review with information collected on signalment, tumor type/location, pre-surgical diagnostics, surgical and pathologic findings for the first excision and scar revision surgeries, and follow-up. Descriptive statistics were generated.

Results

Prior to initial excision, cytology was performed on 38.9% (21/54) of tumors and the initial surgery report rarely described surgical resection margins [14.6% (7/48) of surgeries]. Residual tumor was identified pathologically in 29.6% (16/54) of scars. Local recurrence following scar revision occurred in 3.7% (2/54) of all scars [median follow-up 881.5 d (range: 0 to 3317 d)]; both scars had either complete excision of residual mast cell tumor or no evidence of mast cell tumor on scar revision and neither dog received radiation therapy.

Conclusions

Identification of residual disease was uncommon, and local recurrence was less common than previously reported for incomplete/narrow mast cell tumor excision.

Clinical relevance

Scar revision of unplanned primary excisions appears to yield a high likelihood of durable tumor remission in patients. First opinion practitioners are encouraged to avoid unplanned excisions by informing the surgical plan with cytology of the primary tumor and detailing surgical margin excision which may facilitate revision, if necessary.

Lymph node metastasis in feline cutaneous low-grade mast cell tumours

OBJECTIVES

This retrospective study aimed to determine the incidence of nodal metastatic disease in cats affected by low-grade cutaneous mast cell tumours (MCTs) in our study population.

METHODS

The clinical records of two centres were retrospectively searched for cats with cutaneous MCTs that had undergone lymphadenectomy of enlarged and non-enlarged lymph nodes. All primary tumours were histologically reviewed by two experienced pathologists and graded as high- or low-grade based on the grading system for feline cutaneous MCT. We graded the lymph nodes based on the grading scheme used for canine MCTs and considered HN2 and HN3 nodes to be metastatic. The number of patients with nodal metastasis was calculated.

RESULTS

We identified 17 cats with cutaneous MCT resection and concurrent lymphadenectomy. All 21 MCTs were graded as low grade and 30 nodes were removed, with 12 being considered early or overtly metastatic (HN2 or HN3, respectively). Based on nodal status, 10/17 (59%) cats were affected by nodal metastasis in our population.

CONCLUSIONS AND RELEVANCE

In contrast to previous reports, high percentage of cats with cutaneous MCTs in which lymphadenectomy was performed were presented with metastatic lymph nodes. The clinical relevance of this finding and a potential benefit of lymphadenectomy must be determined in future studies.

Optical coherence tomography for surgical margin evaluation of excised canine cutaneous and subcutaneous tumours

Currently, intraoperative tumour margin imaging is not routinely utilized in veterinary medicine. Optical coherence tomography (OCT) allows for real-time assessment of tissue morphology of 1-2 mm depth. The aims of this study were (1) to compare the histologic and OCT features of excised canine skin and subcutaneous specimens, and (2) to determine the diagnostic accuracy of OCT for surgical margin evaluation. The authors hypothesized that OCT imaging would correlate well with histopathology and that OCT would be sensitive for detection of incomplete margins. Eighty dogs were prospectively enrolled. Tumours were excised, and the surgical margins were imaged using a spectral domain OCT system. The tumour type and completeness of excision were determined by histopathology. Nine blinded observers received training in OCT image interpretation and were then given a set of OCT images and videos. The observers assigned each image/video a grade from 1 (no tumour) to 4 (tumour) and the results were compared to histopathology. The overall median sensitivity and specificity of OCT imaging for detection of incomplete margins were 86.7% and 84.6%, respectively. A potential limitation is that observers had varied experience with OCT image interpretation, ranging from no prior experience to participating in a previous OCT project. OCT is sensitive for detection of incomplete margins and could be a promising real-time surgical margin imaging modality. Further study is needed to evaluate intraoperative applications of OCT and its impact on tumour recurrence and long-term outcome.

Inter-pathologist agreement on diagnosis, classification and grading of canine glioma

Histopathological evaluation of tumours is a subjective process, but studies of inter-pathologist agreement are uncommon in veterinary medicine. The Comparative Brain Tumour Consortium (CBTC) recently published diagnostic criteria for canine gliomas. Our objective was to assess the degree of inter-pathologist agreement on intracranial canine gliomas, utilising the CBTC diagnostic criteria in a cohort of eighty-five samples from dogs with an archival diagnosis of intracranial glioma. Five pathologists independently reviewed H&E and immunohistochemistry sections and provided a diagnosis and grade. Percentage agreement and kappa statistics were calculated to measure inter-pathologist agreement between pairs and amongst the entire group. A consensus diagnosis of glioma subtype and grade was achieved for 71/85 (84%) cases. For these cases, percentage agreement on combined diagnosis (subtype and grade), subtype only and grade only were 66%, 80% and 82%, respectively. Kappa statistics for the same were 0.466, 0.542 and 0.516, respectively. Kappa statistics for oligodendroglioma, astrocytoma and undefined glioma were 0.585, 0.566 and 0.280 and were 0.516 for both low-grade and high-grade tumours. Kappa statistics amongst pairs of pathologists for combined diagnosis varied from 0.352 to 0.839. 8 % of archival oligodendrogliomas and 61% of archival astrocytomas were reclassified as another entity after review. Inter-pathologist agreement utilising CBTC guidelines for canine glioma was moderate overall but varied from fair to almost perfect between pairs of pathologists. Agreement was similar for oligodendrogliomas and astrocytomas but lower for undefined gliomas. These results are similar to pathologist agreement in human glioma studies and with other tumour entities in veterinary medicine.

Luteinizing Hormone Receptor Expression in Neoplastic Mast Cells Is Increased in Spayed and Neutered Dogs

Luteinizing hormone receptors (LHRs) are expressed in canine lymphoma and hemangiosarcoma. We hypothesized that LHR would be expressed in canine mast cell tumors (MCTs) and that more neoplastic mast cells would express LHR in gonadectomized dogs compared with intact dogs. Eleven archived formalin-fixed paraffin-embedded cutaneous MCT tissue sections were processed using routine immunohistochemistry. For both the KIT protein and LHR, the percentage of positive cells for each staining pattern (I-III) was calculated. A Student's t test was used to compare the total percentage of positive cells expressing LHR and KIT in intact and gonadectomized dogs. A one-way analysis of variance was used to compare the percentage of cells within each staining pattern for LHR and KIT in intact and gonadectomized dogs. All MCT expressed LHR. MCT from gonadectomized dogs had a significantly higher percentage of LHR-positive mast cells (84.2 ± 8.7%) compared with MCTs from intact dogs (64.3 ± 4.2%). This is the first study to demonstrate the expression of LHR in canine MCTs and to report that LHR expression is increased in neoplastic mast cells from gonadectomized dogs compared with intact dogs. Future studies are planned to evaluate the functionality of the LHR in canine neoplastic mast cells.

Feline Oncogenomics: What Do We Know about the Genetics of Cancer in Domestic Cats?

Cancer is a significant cause of morbidity and mortality in domestic cats. In humans, an understanding of the oncogenome of different cancer types has proven critical and is deeply interwoven into all aspects of patient care, including diagnostics, prognostics and treatments through the application of targeted therapies. Investigations into understanding the genetics of feline cancers started with cytogenetics and was then expanded to studies at a gene-specific level, looking for mutations and expression level changes of genes that are commonly mutated in human cancers. Methylation studies have also been performed and together with a recently generated high-quality reference genome for cats, next-generation sequencing studies are starting to deliver results. This review summarises what is currently known of the genetics of both common and rare cancer types in cats, including lymphomas, mammary tumours, squamous cell carcinomas, soft tissue tumours, mast cell tumours, haemangiosarcomas, pulmonary carcinomas, pancreatic carcinomas and osteosarcomas. Shining a spotlight on our current understanding of the feline oncogenome will hopefully serve as a springboard for more much-needed research into the genetics of cancer in domestic cats.

Incomplete histological margins following planned narrow excision of canine appendicular soft tissue sarcomas and mast cell tumors, using the residual tumor classification scheme

OBJECTIVE

To describe the frequency of incomplete histological margins following planned narrow excision (PNE) of mast cell tumors (MCTs) and soft tissue sarcomas (STSs), and to assess the residual tumor classification (R) scheme for reporting histological margins in clinical cases.

STUDY DESIGN

Retrospective clinical study.

SAMPLE POPULATION

Forty-four client-owned dogs with 47 masses.

METHODS

Medical records of dogs undergoing planned narrow excision of STSs and MCTs were reviewed (2016-2019). Histologic specimens were reviewed by a single pathologist and assigned R scoring (histologically incomplete/R1 margins defined as "tumor on ink").

RESULTS

Six out of 23 (26%) MCT PNEs and 10/42 (42%) of STS PNEs resulted in R1 margins. R1 margins were more likely when performing PNE with 6-10 mm lateral measured surgical margins (LMSMs) versus 0-5 mm LMSM for MCTs (1/14 vs 5/9), but not STSs (3/7 vs 7/17) (P = .049). The R scheme resulted in higher retrospective percentage agreement in histological reporting than defining incomplete histological margin as tumor cells within ≤1 mm of the margin (83% vs 68% agreement). Complications occurred in 12/47 surgeries, with none requiring additional surgery. Tumors recurred in 3/18 (17%) STSs and 2/18 (11%) MCTs.

CONCLUSION

Fewer R1 margins were obtained when PNE with LMSM of 6-10 mm was performed for mast cell tumors. The use of the R scheme increased agreement in histopathological margin assessment.

CLINICAL SIGNIFICANCE

Planned narrow excision is a viable technique for histopathological diagnosis of appendicular soft tissue sarcomas and mast cell tumors for limb salvage.

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.

Expression of cannabinoid receptors CB1 and CB2 in canine cutaneous mast cell tumours

Cannabinoid receptors (CB1 and CB2) belong to endocannabinoid system (ECS), which is also composed from endocannabinoids and the enzymatic systems involved in their biosynthesis and degradation. The expression of CB1 and CB2 have been previously identified in normal canine mast cell and in atopic dermatitis. Canine cutaneous mast cell tumours (cMCTs) are among the most common cutaneous neoplasms in dogs and have a highly variable clinical behaviour. Expression of CB1-CB2 was assessed by means of immunohistochemistry in thirty-seven dogs (from 2019 to 2021) with proven histological diagnosis of cMCT. Dogs were divided in two groups according to the Kiupel's grading system: high-grade (HG) cMCT and low-grade (LG) cMCT. A semiquantitative (score 0-3) and quantitative assessment of immunoreactivity (IR) was performed for each case. Our results show that there CB1 and CB2 are highly expressed in LG- cMCT, in contrast to HG- cMCT.

Mutations in Exons 8 and 11 of c-kit Gene in Canine Subcutaneous Mast Cell Tumors and Their Association with Cell Proliferation

The prognostic significance of internal tandem duplication (ITD) mutations in exons 8 and 11 of c-kit has been well-described for canine cutaneous mast cell tumors (MCTs), but c-kit mutations have rarely been reported in subcutaneous MCTs. The objective of this study was to identify the prevalence of ITD mutations in exons 8 and 11 of c-kit in canine subcutaneous MCTs and to investigate its association with histologic grade, KIT pattern, and proliferation markers. ITD mutations in exons 8 and 11 of c-kit, mitotic count, Ki67 index, AgNOR number, Ki67xAgNOR score, KIT pattern, and histologic grade (two-tier system) were retrospectively recorded for 216 dogs with subcutaneous MCTs. ITD mutations in exons 8 and 11 of c-kit were detected in 23 (10.6%) and 12 (5.56%) subcutaneous MCTs, respectively. Exon 11 mutations were significantly associated with Kiupel high grade (p < 0.001) and increased mitotic count (p < 0.001) compared to subcutaneous MCTs with no mutations in exons 8 or 11 (p = 0.002) or subcutaneous MCTs with a mutation in exon 8 (p = 0.001). There was no significant association of either c-kit mutation with KIT patterns or proliferation activity. This study identified a higher prevalence of ITD mutations in exons 8 and 11 of c-kit in subcutaneous MCTs than previously reported. Like their cutaneous counterpart, subcutaneous MCTs with exon 11 mutations were more likely to be histologically high grade and have a higher mitotic count, whereas such associations were not observed in subcutaneous MCTs with exon 8 mutations.

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.

Tumour Incidence in Dogs in Germany: a Retrospective Analysis of 109,616 Histopathological Diagnoses (2014-2019)

Characterization of a tumour entity is based on the precise histopathological diagnosis taking into account the signalment of the diseased animal. The present study is a comprehensive, up-to-date statistical investigation on the type, frequency and breed distribution of neoplasia in dogs in Germany. The histopathological datasets of 109,616 German canine tissue samples (2014-2019) were processed and statistically examined in retrospect. Non-neoplastic diseases were found in 38,650 samples (35.3%) and 70,966 neoplasms (64.7%) were diagnosed. The most common neoplasms were mammary tumours (21.9%), benign epithelial skin tumours (15.4%), mast cell tumour (9.7%), histiocytoma (7.0%), soft tissue sarcoma (5.8%), lipoma (5.8%), melanocytic tumours (5.2%) and odontogenic tumours (4.7%). In general, Beagles, Magyar Vizslas, Boxers, Schnauzers, Spaniels, French Bulldogs and Golden Retrievers had an increased risk of neoplasia (odds ratio 1.17-1.46; all: P ≤0.001) compared with crossbreed dogs. In particular, Boxers, Golden Retrievers, Rottweilers and Schnauzers were often affected by malignant neoplasms, whereas some breeds (eg, West Highland White Terrier, Magyar Vizsla, Chihuahua, Dachshund and Yorkshire Terrier) were frequently affected by numerous benign tumour types. Despite the known risk of haemangiosarcoma in German Shepherd Dogs, other malignant tumours were rare in this breed. Depending on the type of tumour, some purebred dog breeds can have an increased, reduced or identical risk for certain neoplasms compared with crossbreeds. Discussion of breed predispositions to tumour diseases must therefore be conducted critically and with a view to clinical relevance.

Inclusion of fibroblasts and collagen fibrils in the cytologic grading of canine cutaneous mast cell tumors

BACKGROUND

Fibroblasts and/or collagen fibrils have not been included in previous cytologic grading schemes of canine mast cell tumors (MCTs), and their association with biological behavior is broadly debated.

OBJECTIVES

This study aimed to evaluate the cytologic findings of canine MCT, with emphasis on the microenvironment, and propose a novel cytologic grading system correlated with mortality and histologic grade.

MATERIAL AND METHODS

Cytology smears of canine cutaneous MCTs were retrospectively reviewed and compared with their histopathologic counterparts using Cohen´s Kappa test. One-year survival rates were also compared with the cytologic and histopathologic variables using Pearson´s correlation test.

RESULTS

From 92 first-occurrence canine cutaneous MCTs, the five features most associated with mortality were selected for a new grading system. The five features were cytoplasmic granulation, fibroblast and/or collagen fibril concentrations, and the presence of mitotic figures, multinucleation, and karyomegaly. Among concordant histopathologic and cytologic cases (ie, the same grades using both systems), mortality rates were 2.6% (1/38) for low-grade and 71.4% (10/14) for high-grade cases (P < 0.001, chi-square). For false-negative and false-positive results, mortality rates were 33% (1/3) and 45% (5/11), respectively (P = 0.707).

CONCLUSIONS

Unlike the Camus cytologic grading system, the present amendment excluded binucleation and included fibroblasts and/ or collagen fibrils, which in higher concentrations were associated with increased survival and a low histopathologic grade. Cytologic grading with the inclusion of fibroblast and collagen fibril concentrations correlated with survival, as did the Camus cytologic and Kiupel histopathologic grades; however, further studies are needed to confirm the prognostic value of this novel cytologic grading scheme.

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.

Activating Mutation in the Receptor Tyrosine Kinase FLT3 with Clinicopathological Relevance in Canine Mast Cell Tumors

Recent research has focused on the receptor tyrosine kinase (RTK) KIT which is involved in the pathogenesis of canine mast cell tumors (MCT). However, the role of other RTKs in this neoplasm remains unclear. The present study aimed to determine the frequency of FLT3 mutations and to evaluate the mutational status and clinicopathological relevance of canine MCT patients. There were a total of 20 cases that were cytologically and histopathological diagnosed as canine MCTs; genomic polymerase chain reaction (PCR) and Sanger sequencing were used to identify mutations. For the juxtamembrane (JM) domain, the FLT3 14/15 primer pair was used to investigate exon 14/15 loci. Based on genomic PCR amplification of exon 14/15 and 20 of the FLT3 gene and Sanger sequencing of 20 cases of canine MCTs, the overall frequency of FLT3 mutation in canine MCTs was 75%. The majority of FLT3 mutations (70%) were internal tandem duplications (ITD) of the JM domain, while one case arose from deletion mutations of the tyrosine kinase domain (TKD). However, double mutations were not observed in this study. Furthermore, there is also clinicopathological relevance to MCT dogs carrying FLT3-ITD mutations, showing a tendency toward leukocytosis due to neutrophilia, and resembling human acute myeloid leukemia (AML) with FLT3-ITD mutations. A subset of MCTs with FLT3-ITD mutations, showing an enhanced signal of phosphorylated ERK1/2 identified by immunoblotting, suggests that an activating mutation may be driven by a distinct signal of the ERK pathway. Our results indicate that FLT3-ITD mutation is an oncogenic driver of canine MCTs, and that it shares some clinicopathologic features with human AML. These findings may offer new opportunities for further studies on canine mast cell tumorigenesis and a novel therapeutic target for canine MCT cases harboring FLT3-ITD mutations.

Sentinel Lymph Node Biopsy Is Feasible in Dogs with Scars from Prior Local Excision of Solid Malignancies

Simple Summary

Sentinel lymph node (SLN) excision is gaining relevance in the management of various canine malignancies due to its recognized impact on staging and treatment choices. However, the technologies to perform SLN mapping are only available to a few referral centers, and there is increasing demand for secondary nodal staging after prior tumor excision at the primary care institution. This retrospective study investigated the feasibility and usefulness of SLN biopsy in dogs with surgical scars resulting from the removal of various solid tumors referred for further staging and/or adjuvant treatment options. Thirty-three dogs with 34 scars underwent SLN biopsy at a median of 50 days after primary tumor excision. An SLN was identified for 31/34 scars, translating to a detection rate of 91.2%. Metastases were identified with histopathology in 13/31 dogs (41.9%) and they all had an excision of a mast cell tumor. SLN biopsy should be suggested in dogs presenting with scars from prior solid tumor excision, considering the observed detection rate and the importance of knowing the metastatic status of the SLN in oncological diseases.

Abstract

Sentinel lymph node (SLN) biopsy is a well-established staging tool in canine oncology. This study aims to explore the feasibility of SLN biopsy in dogs with scars from prior excised solid malignancies that were referred for further tumor staging and/or adjuvant treatment options. Mapping was either performed using radiopharmaceutical, methylene blue, and/or near-infrared fluorescent (NIRF) imaging. Thirty-three dogs with 34 scars from prior excision of the mast cell tumor (MCT) (n = 29), soft tissue sarcoma (n = 2), oral melanoma (n = 1), subungual melanoma (n = 1), and mammary adenocarcinoma (n = 1) were retrospectively enrolled. Primary treatment consisted of curative intent/wide tumor excisions in 50.0% of dogs and marginal excision in the remaining 50.0%. The median time between tumor excision and SLN biopsy was 50 days (range 17–110 days). The procedure was successful in 31/34 scars, translating to a detection rate of 91.2%. The SLN did not correspond to the regional lymph node in 19/31 scars (61.3%). SLN metastases were histologically identified in 13/31 (41.9%) dogs, all of them affected by MCT. Based on our results, SLN biopsy using lymphoscintigraphy/methylene blue and/or NIRF is feasible in dogs presenting with scars from the prior surgical excision of solid tumors, and should be suggested for accurate nodal staging.

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.

Tolerability and Effects of 2-Aminoethyl Dihydrogen Phosphate in Dogs With Mast Cell Tumors

Canine mast cell tumor is a malignant neoplasm, and a gold standard treatment remains to be determined despite the proposed chemotherapies or other therapies in dogs. This study aimed to determine therapeutic, adverse effects and toxicity, tumor-free, and overall survival times of 10 dogs with surgically excised mast cell tumors evaluated by histopathological/immunohistochemistry and treated with four weekly intravenous administrations of 2-Aminoethyl Dihydrogen Phosphate (70 mg/kg) as adjuvant therapy. No adverse events were noted. Laboratory changes were limited (p < 0.05) in red blood cell, hemoglobin, and platelet counts. Mean tumor-free and overall survival were 599.1 ± 469 and 755.5 ± 423.5 days, respectively. In conclusion, 2-Aminoethyl Dihydrogen Phosphate administration was safe in dogs. However, 2-Aminoethyl Dihydrogen Phosphate was not sufficiently effective to prevent a recurrence, new tumor, or metastasis of canine mast cell tumors with poor immunohistochemical prognostic factors.

Near-infrared fluorescent image-guided lymph node dissection compared with locoregional lymphadenectomies in dogs with mast cell tumours

Objectives

Near‐infrared fluorescent imaging has been described for intraoperative mapping of the draining lymph nodes in human cancer and canine oral tumours. The aim of this study was to retrospectively describe the results of lymphadenectomies in dogs with mast cell tumours treated either by standard unguided locoregional lymph node dissection or near‐infrared fluorescent image‐guided lymph node dissection.

Methods

Medical records between 2012 and 2020 were reviewed for dogs that were presented for surgical resection of mast cell tumours with concurrent lymphadenectomy either with (near‐infrared fluorescent image‐guided lymph node dissection) or without near‐infrared fluorescence image guidance (lymph node dissection). The number and location of lymph nodes planned for surgical dissection and actually dissected nodes, presence of metastases and perioperative complications were recorded.

Results

Thirty‐five patients underwent near‐infrared fluorescent image‐guided lymph node dissection, and 43 lymph node dissections. The number of nodes preoperatively planned for resection were 70 and 68, respectively. Fifty‐eight of those (83%) were identified during near‐infrared fluorescent image‐guided lymph node dissection procedures, compared with 50 (74%) during lymph node dissection. near‐infrared fluorescent image‐guided lymph node dissection resulted in resection of additional fluorescent nodes not corresponding to locoregional nodes in 15 of 35 dogs. Using near‐infrared fluorescent image‐guided lymph node dissection, we identified at least one metastatic node in 68% of dogs (24 of 35) compared with 33% (14 of 43) when lymph node dissection was used without imaging. No complications related to near‐infrared fluorescent imaging were reported.

Clinical Significance

The present study suggests that near‐infrared imaging is a promising technique for intraoperative detection of the draining lymph nodes in dogs with mast cell tumours. Further validation of the technique is required to assess if near‐infrared fluorescent imaging can detect the true sentinel lymph node.

Lymphadenectomy improves outcome in dogs with resected Kiupel high-grade cutaneous mast cell tumours and overtly metastatic regional lymph nodes

INTRODUCTION

Historically, the prognosis for dogs with stage II Kiupel high-grade cutaneous mast cell tumours has been considered poor.

OBJECTIVES

The aim of this study was to explore the impact of lymphadenectomy on outcome in dogs with Kiupel high-grade cutaneous mast cell tumours and overt regional lymph node metastasis.

MATERIAL AND METHODS

Data from dogs with completely staged Kiupel high-grade cutaneous mast cell tumours with overt and/or certain regional lymph node metastasis undergoing excision of the primary tumours and adjuvant medical treatment were extracted. Dogs with a cytological diagnosis of regional lymph node metastasis that did not undergo lymphadenectomy were compared with dogs that underwent lymphadenectomy and had a histological diagnosis of overt lymph node metastasis.

RESULTS

Forty-nine dogs were included, 18 did not undergo lymphadenectomy while 31 underwent lymphadenectomy. Median time to progression was significantly shorter in dogs that did not undergo lymphadenectomy (150 days, 95% confidence interval: 129 to 170) compared to the other dogs (229 days, 95% confidence interval: 191 to 266). Median survival time was also shorter in dogs that did not undergo lymphadenectomy (250 days, 95% confidence interval: 191 to 308) compared to dogs that underwent lymphadenectomy (371 days, 95% confidence interval: 311 to 430). On multivariable analysis, lack of lymphadenectomy was associated with higher risk of overall tumour progression (hazard ratio: 2.05, 95% confidence interval: 1.02 to 4.13), nodal progression (hazard ratio: 3.4, 95% confidence interval: 1.65 to 7.02) and tumour-related death (hazard ratio 3.63, 95% confidence interval: 1.72 to 7.66), whereas tumour size was associated with higher risk of local recurrence (hazard ratio: 3.61, 95% confidence interval: 1.06 to 13).

CLINICAL SIGNIFICANCE

Regional lymphadenectomy may improve outcome in dogs with biologically aggressive cutaneous mast cell tumours.

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.

Grading Systems for Canine Urothelial Carcinoma of the Bladder: A Comparative Overview

The relationship between tumor morphology and clinical behavior is a key point in oncology. In this scenario, pathologists and clinicians play a pivotal role in the identification and testing of reliable grading systems based on standardized parameters to predict patient prognosis. Dogs with bladder urothelial carcinoma (BUC) were recently proposed as a "large animal" model for the study of human BUCs due to the similar morphology and metastasis locations. BUC grading systems are consolidated in human medicine, while in veterinary medicine, the BUC grading systems that have been proposed for canine tumors are not yet applied in routine diagnostics. These latter systems have been proposed, decade by decade, over the last thirty years, and the reason for their scarce application is mainly related to a lack of specific cutoff values and studies assessing their prognostic relevance. However, for any prognostic study, reliable grading is necessary. The aim of the present article was to give an overview of the BUC grading systems available in both human and veterinary pathology and provide an extensive description and a critical evaluation to support veterinary researchers in the choice of possible grading systems to apply in future studies on canine BUCs.

Review of diagnostic histologic features of cutaneous round cell neoplasms in dogs

Cutaneous round cell neoplasms (RCNs) are among the most common skin tumors of dogs. Although a diagnosis can be made in most cases following the examination of H&E-stained routine samples, less-differentiated neoplasms can exhibit overlapping morphologic features that may be challenging to the pathologist, and require immunohistochemistry or molecular testing to reach a final diagnosis. Many patients with cutaneous RCNs are initially seen by a general practitioner and are not referred to a veterinary teaching hospital until a diagnosis has been made. For this reason, anatomic pathology residents at some academic or other training institutions may not be exposed frequently to RCNs during the surgical biopsy service as part of their residency training. In an attempt to fill that gap, here we review the key routine histologic features of canine cutaneous RCNs.