Outcome following removal of canine spindle cell tumours in first opinion practice: 104 cases

Keeping Pathologists in the Loop and an Adaptive F1-Score Threshold Method for Mitosis Detection in Canine Perivascular Wall Tumours

Performing a mitosis count (MC) is the diagnostic task of histologically grading canine Soft Tissue Sarcoma (cSTS). However, mitosis count is subject to inter- and intra-observer variability. Deep learning models can offer a standardisation in the process of MC used to histologically grade canine Soft Tissue Sarcomas. Subsequently, the focus of this study was mitosis detection in canine Perivascular Wall Tumours (cPWTs). Generating mitosis annotations is a long and arduous process open to inter-observer variability. Therefore, by keeping pathologists in the loop, a two-step annotation process was performed where a pre-trained Faster R-CNN model was trained on initial annotations provided by veterinary pathologists. The pathologists reviewed the output false positive mitosis candidates and determined whether these were overlooked candidates, thus updating the dataset. Faster R-CNN was then trained on this updated dataset. An optimal decision threshold was applied to maximise the F1-score predetermined using the validation set and produced our best F1-score of 0.75, which is competitive with the state of the art in the canine mitosis domain.

Novel 3D Custom-Made Silicone Tumor Model as a Support for Teaching Surgical Oncology Principles

Alternative laboratory teaching methods are becoming increasingly desirable and effective in medical education environments. While ethical concerns associated with the use of live animals in terminal surgery laboratories have been reduced with cadaveric models, availability, and lack of pathology can limit their ability to adequately convey surgical principles and replicate clinical training. We have developed a three-dimensional (3D) custom-made silicone soft tissue tumor model using 3D-printed molds derived from canine soft tissue sarcoma computed tomography images. This novel teaching model allows users to apply surgical oncology principles and perform basic technical tasks such as incisional biopsy, margin demarcation, marginal and wide surgical excision, and inking of surgical margins. A large cohort of students in addition to a small number of professional veterinarians at different levels of specialty training followed the laboratory guidelines and evaluated the simulated tumor model based on a qualitative survey. All participants were able to successfully complete the practical training. The model also allowed the students to identify and correct technical errors associated with biopsy sampling and margin dissection, and to understand the clinical impacts related to those errors. Face and content validity of the model were assessed using Likert-style questionnaires with overall average instructors' scores of 3.8/5 and 4.6/5, respectively. Content validity assessment of the model by the students approximated instructors' evaluation with an overall average score of 4.4/5. This model development emphasizes the efficacy of alternative non-cadaveric laboratory teaching tools and could become a valuable aid in the veterinary curricula.

Development of a Nomogram to Predict the Outcome for Patients with Soft Tissue Sarcoma

Soft tissue sarcomas (STSs) are common cutaneous or subcutaneous neoplasms in dogs. Most STSs are initially treated by surgical excision, and local recurrence may develop in almost 20% of patients. Currently, it is difficult to predict which STS will recur after excision, but this ability would greatly assist patient management. In recent years, the nomogram has emerged as a tool to allow oncologists to predict an outcome from a combination of risk factors. The aim of this study was to develop a nomogram for canine STSs and determine if the nomogram could predict patient outcomes better than individual tumour characteristics. The current study provides the first evidence in veterinary oncology to support a role for the nomogram to assist with predicting the outcome for patients after surgery for STSs. The nomogram developed in this study accurately predicted tumour-free survival in 25 patients but failed to predict recurrence in 1 patient. Overall, the sensitivity, specificity, positive predictive, and negative predictive values for the nomogram were 96%, 45%, 45%, and 96%, respectively (area under the curve: AUC = 0.84). This study suggests a nomogram could play an important role in helping to identify patients who could benefit from revision surgery or adjuvant therapy for an STS.

Naturally occurring canine sarcomas: Bridging the gap from mouse models to human patients through cross-disciplinary research partnerships

Fueled by support from the National Cancer Institute's "Cancer Moonshot" program, the past few years have witnessed a renewed interest in the canine spontaneous cancer model as an invaluable resource in translational oncology research. Increasingly, there is awareness that pet dogs with cancer provide an accessible bridge to improving the efficiency of cancer drug discovery and clinical therapeutic development. Canine tumors share many biological, genetic, and histologic features with their human tumor counterparts, and most importantly, retain the complexities of naturally occurring drug resistance, metastasis, and tumor-host immune interactions, all of which are difficult to recapitulate in induced or genetically engineered murine tumor models. The utility of canine models has been particularly apparent in sarcoma research, where the increased incidence of sarcomas in dogs as compared to people has facilitated comparative research resulting in treatment advances benefitting both species. Although there is an increasing awareness of the advantages in using spontaneous canine sarcoma models for research, these models remain underutilized, in part due to a lack of more permanent institutional and cross-institutional infrastructure to support partnerships between veterinary and human clinician-scientists. In this review, we provide an updated overview of historical and current applications of spontaneously occurring canine tumor models in sarcoma research, with particular attention to knowledge gaps, limitations, and growth opportunities within these applications. Furthermore, we propose considerations for working within existing veterinary translational and comparative oncology research infrastructures to maximize the benefit of partnerships between veterinary and human biomedical researchers within and across institutions to improve the utility and application of spontaneous canine sarcomas in translational oncology research.

Evaluating the relevance of surgical margins. Part one: The problems with current methodology

The goal of cancer surgery is to achieve a "clean" microscopic resection, with no residual tumour remaining in the wound. To achieve that goal, the surgeon typically incorporates a measured buffer of grossly normal tissue about the entire circumference of the tumour. Microscopic analysis of the resection boundaries is then performed to determine if all traces of the tumour have been completely removed. This analysis is thought to provide a surrogate indication as to the likelihood for that tumour to recur after surgery. However, it is recognised that tumour recurrence may not occur even when microscopic evidence of tumour has been identified at the resection margins, and recurrence can also occur when conventional histology has considered the tumour to have been completely removed. The explanations for this dichotomy are numerous and include technical and practical limitations of the processing methodology, and also several surgeon-related and tumour-related reasons. Ultimately, the inability to confidently determine when a tumour has been removed sufficiently to prevent recurrence can impact on the ability to provide owners with confident treatment advice. In this article, the authors describe the challenges with defining the true extent of the tumour margin from the perspective of the surgeon, the pathologist and the tumour. The authors also provide an analysis of why our current efforts to ensure that all traces of the local tumour have been successfully removed may provide an imperfect assessment of the risk of recurrence.

Defining the relevance of surgical margins. Part two: Strategies to improve prediction of recurrence risk

Due to the complex nature of tumour biology and the integration between host tissues and molecular processes of the tumour cells, a continued reliance on the status of the microscopic cellular margin should not remain our only determinant of the success of a curative-intent surgery for patients with cancer. Based on current evidence, relying on a purely cellular focus to provide a binary indication of treatment success can provide an incomplete interpretation of potential outcome. A more holistic analysis of the cancer margin may be required. If we are to move ahead from our current situation - and allow treatment plans to be more intelligently tailored to meet the requirements of each individual tumour - we need to improve our utilisation of techniques that either improve recognition of residual tumour cells within the surgical field or enable a more comprehensive interrogation of tumour biology that identifies a risk of recurrence. In the second article in this series on defining the relevance of surgical margins, the authors discuss possible alternative strategies for margin assessment and evaluation in the canine and feline cancer patient. These strategies include considering adoption of the residual tumour classification scheme; intra-operative imaging systems including fluorescence-guided surgery, optical coherence tomography and Raman spectroscopy; molecular analysis and whole transcriptome analysis of tissues; and the development of a biologic index (nomogram). These techniques may allow evaluation of individual tumour biology and the status of the resection margin in ways that are different to our current techniques. Ultimately, these techniques seek to better define the risk of tumour recurrence following surgery and provide the surgeon and patient with more confidence in margin assessment.

Feline Soft Tissue Sarcomas: A Review of the Classification and Histological Grading, with Comparison to Human and Canine

Simple Summary

Soft tissue sarcomas are a common form of cancer arising in the skin and connective tissues of domestic cats. Soft tissue sarcomas encompass a group of different histological subtypes of tumours, which can behave in a range of different ways in the patient. In dogs and in humans, this group of tumours can be given a histological score (“grade”) at the time of diagnosis, which is prognostic, but there is no equivalent, well-established grading system for these tumours in cats. This review looks at soft tissue sarcomas in terms of which histological subtypes of tumour should be included in this group, and how pathologists approach their grading, comparing feline tumours with their human and canine counterparts.

Abstract

Soft tissue sarcomas are one of the most commonly diagnosed tumours arising in the skin and subcutis of our domestic cats, and are malignant neoplasms with a range of histological presentations and potential biological behaviours. However, unlike their canine and human counterparts, there is no well-established histological grading system for pathologists to apply to these tumours, in order to provide a more accurate and refined prognosis. The situation is further complicated by the presence of feline injection site sarcomas as an entity, as well as confusion over terminology for this group of tumours and which histological types should be included. There is also an absence of large scale studies. This review looks at these tumours in domestic cats, their classification and histological grading, with comparisons to the human and canine grading system.

Mediastinal Fibrosarcoma in a Dog–Case Report

This represents the first published case report of mediastinal fibrosarcoma in a dog. An 8-year-old male neutered mixed breed dog was presented for evaluation of lethargy and increased panting. Thoracic focused assessment with sonography for trauma revealed moderate pleural effusion. Thoracic radiograph findings were suggestive of a cranial mediastinal mass. Computed tomography revealed a mass within the right ventral aspect of the cranial mediastinum. On surgical exploration, a cranial mediastinal mass with an adhesion to the right cranial lung lobe was identified and removed en-bloc using a vessel sealant device and requiring a partial lung lobectomy. Histopathology results described the cranial mediastinal mass as fibrosarcoma with reactive mesothelial cells identified within the sternal lymph node. The patient was treated with systemic chemotherapy following surgical removal. To date, the dog has survived 223 days following diagnosis with recurrence noted 161 days following diagnosis and radiation therapy was initiated. Primary cranial mediastinal fibrosarcoma while a seemingly rare cause of thoracic pathology in dogs, should be considered in the differential diagnosis for a cranial mediastinal mass.

Intersurgeon agreement in determining 3 cm surgical margins of subcutaneous tumors in dogs

OBJECTIVE

To evaluate intersurgeon agreement in performing a 3 cm wide surgical excision for subcutaneous malignancies in dogs.

STUDY DESIGN

Prospective, blinded, randomized, clinical study.

ANIMALS

Client-owned dogs with subcutaneous tumors undergoing curative-intent, wide surgical excision between April 2019 to March 2020.

METHODS

Four surgeons, instructed to perform a 3 cm wide excision, each sequentially indicated their proposed skin incision locations around subcutaneous tumors, without knowledge of the other surgeons' proposed incisions. A tripod-mounted camera and laser positioning system were used to photograph each surgeon's proposed margin length. A random-effects model was used to estimate the standard deviation of margin lengths that would be expected from a random sample of surgeons.

RESULTS

Each of the four surgeons provided 33 independent radial measurements from 11 tumors (six soft tissue sarcomas and five mast cell tumors), for a total of 132 radial measurements. No individual surgeon consistently proposed longer or shorter margin incision locations. The prediction interval for a future margin measurement was 6 mm, implying that the 95% confidence interval of an individual surgeon's margin length would be within ±6 mm of the mean margin length from a random sample of surgeons.

CONCLUSION

Ninety-five percent of surgeons would be expected to deliver a surgical dose between 2.4-3.6 cm, for a theoretically uniform surgical dose of 3 cm wide margins.

CLINICAL SIGNIFICANCE

Surgical doses are likely to vary at clinically relevant levels among surgeons, complicating design and interpretation of studies attempting to identify an ideal surgical dose.

Intraoperative assessment of canine soft tissue sarcoma by deep learning enhanced optical coherence tomography

Soft tissue sarcoma (STS) is a locally aggressive and infiltrative tumour in dogs. Surgical resection is the treatment of choice for local tumour control. Currently, post-operative pathology is performed for surgical margin assessment. Spectral-domain optical coherence tomography (OCT) has recently been evaluated for its value for surgical margin assessment in some tumour types in dogs. The purpose of this study was to develop an automatic diagnosis system that can assist clinicians in real-time for OCT image interpretation of tissues at surgical margins. We utilized a ResNet-50 network to classify healthy and cancerous tissues. A patch-based approach was adopted to achieve accurate classification with limited training data (80 cancer images, 80 normal images) and the validation set (20 cancer images, 20 normal images). The proposed method achieved an average accuracy of 97.1% with an excellent sensitivity of 94.3% on the validation set; the quadratic weighted κ was 0.94 for the STS diagnosis. In an independent test data set of 20 OCT images (10 cancer images, 10 normal images), the proposed method correctly differentiated all the STS images. Furthermore, we proposed a diagnostic curve, which could be evaluated in real-time to assist clinicians in detecting the specific location of a lesion. In short, the proposed method is accurate, operates in real-time and is non-invasive, which could be helpful for future surgical guidance.

Prevalence of pulmonary nodules suggestive of metastasis at presentation in dogs with cutaneous or subcutaneous soft tissue sarcoma

OBJECTIVE

To investigate the prevalence of pulmonary nodules suggestive of metastasis at the time of initial presentation in dogs with cutaneous or subcutaneous soft tissue sarcomas (STSs) and no previous related thoracic diagnostic imaging.

ANIMALS

146 client-owned dogs with a cutaneous or subcutaneous STS.

PROCEDURES

Medical records were retrospectively searched to identify dogs with STSs that underwent initial thoracic diagnostic imaging when presented for referral examination between September 2014 and March 2018. Data collected included patient and tumor characteristics. Results were evaluated for dogs grouped on the basis of variables of interest (eg, STS grade, duration, or history).

RESULTS

Initial thoracic imaging was performed with CT (131/146 [89.7%]) or radiography (15 [10.3%]). Although the presence or absence of pulmonary nodules suggestive of metastasis on thoracic imaging was uncertain in 9 dogs, it was certain in the remaining 137 dogs, with nodules present in 16 (11.7%) dogs (5/77 [6%] with grade 1 STSs, 2/36 [6%] with grade 2 STSs, and 9/24 [38%] with grade 3 STSs). The odds of such pulmonary nodules being present on initial examination were higher (OR, 10.8 and 3.14, respectively) for dogs with grade 3 STSs (vs grade 1 or 2 STSs) and for dogs with an STS duration > 3 months (versus ≤ 3 months).

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that pulmonary staging was a low-yield diagnostic procedure for dogs with grade 1 or 2 cutaneous or subcutaneous STSs, especially when tumors had been present for ≤ 3 months.

Review of Histological Grading Systems in Veterinary Medicine

Tumor grading is a method to quantify the putative clinical aggressiveness of a neoplasm based on specific histological features. A good grading system should be simple, easy to use, reproducible, and accurately segregate tumors into those with low versus high risk. The aim of this review is to summarize the histological and, when available, cytological grading systems applied in veterinary pathology, providing information regarding their prognostic impact, reproducibility, usefulness, and shortcomings. Most of the grading schemes used in veterinary medicine are developed for common tumor entities. Grading systems exist for soft tissue sarcoma, osteosarcoma, multilobular tumor of bone, mast cell tumor, lymphoma, mammary carcinoma, pulmonary carcinoma, urothelial carcinoma, renal cell carcinoma, prostatic carcinoma, and central nervous system tumors. The prognostic relevance of many grading schemes has been demonstrated, but for some tumor types the usefulness of grading remains controversial. Furthermore, validation studies are available only for a minority of the grading systems. Contrasting data on the prognostic power of some grading systems, lack of detailed instructions in the materials and methods in some studies, and lack of data on reproducibility and validation studies are discussed for the relevant grading systems. Awareness of the limitations of grading is necessary for pathologists and oncologists to use these systems appropriately and to drive initiatives for their improvement.

Comparative Evaluation of the Cytological, Histopathological and Immunohistochemical Findings of Canine Cutaneous and Subcutaneous Masses

In this study, we compared the cytological, histopathological, and immunohistochemical diagnoses of 71 canine cutaneous and subcutaneous masses. Cytological diagnoses included 56 tumors (21 mesenchymal, 15 epithelial, 16 round cell, four melanocytic), 13 inflammatory reactions, and two cysts. Of the 21 cytologically diagnosed mesenchymal tumors, three were later confirmed non-tumoral (hematoma, granulation tissue, fibroepithelial polyp). Thirteen out of 15 epithelial tumors were correctly diagnosed cytologically, whereas two cases were confirmed to be non-tumoral (fibroepithelial polyp, granulation tissue) after histopathological examination. One mast cell tumor was later confirmed as fibrous hyperplasia; diagnoses were correct in other round cell tumors. Cytological diagnoses were correct for all melanocytic tumors and cystic lesions. Five cases which had been cytologically diagnosed as inflammatory reactions were diagnosed as tumors (lymphoma, papilloma, sebaceous adenoma, and squamous cell carcinoma) after histopathological examination. Immunohistochemistry confirmed the histopathological diagnoses of all epithelial and round cell tumors, while the diagnoses of six mesenchymal tumors were changed after the immunohistochemical examination. The total accuracy of cytology in the diagnosis of tumoral/non-tumoral masses was 84.5%, and the accuracy in the determination of benign/malignant behavior was 83%. Diagnostic accordance between histopathology and immunohistochemistry was 86.6%. High success rates obtained with cytological diagnoses prove that cytology is a reliable diagnostic tool. The main diagnostic challenge remains with mesenchymal tumors and tumors accompanied by inflammatory reactions. The results suggest that immunohistochemistry is fundamental for diagnoses of most mesenchymal tumors.

Evaluation of the neoplastic infiltration of the skin overlying canine subcutaneous soft tissue sarcomas: An explorative study

Studies regarding the neoplastic infiltration of the skin overlying canine subcutaneous soft tissue sarcoma (sSTS) are lacking. In case of the absence of tumor infiltration, there would be the possibility of leaving this unaffected skin in place, thus simplifying surgery. The aim of the study was to investigate whether the skin overlying sSTSs is infiltrated by neoplastic cells. Dogs with sSTSs treated surgically were prospectively enrolled. After excision, the skin was dissected from the tumor along the natural surgical plane of cleavage and histologically evaluated. Twenty-nine dogs with an sSTS were included (22 grade I, 6 grade II, and 1 grade III). The sSTS-overlying skin was not tumor-infiltrated in 14/29 cases (48.3%). A higher frequency of infiltration was observed in higher grade sSTSs (grades II and III, 100%; P = .006); nevertheless, 8/22 grade I sSTSs (36%) also showed cutaneous infiltration. This infiltration involved the dermis of the skin directly in contact with the tumor (multifocal in 11 and diffuse in four cases). Although the cutaneous tumor infiltration is less frequent in grade I sSTSs and a wide excision may still be the safest treatment for any sSTS for a greater possibility of local control, this study opens the possibility to a less aggressive cutaneous excision, but still with a local curative intent, as only the skin directly in contact with the sSTS has been proven to be tumor-infiltrated. Additional studies are warranted to confirm that excision of only this skin may guarantee a complete local control, especially in lower-grade sSTSs.

Diagnostic accuracy of optical coherence tomography for assessing surgical margins of canine soft tissue sarcomas in observers of different specialties

OBJECTIVE

To determine the diagnostic accuracy of optical coherence tomography (OCT) to assess surgical margins of canine soft tissue sarcoma (STS) and determine the influence of observer specialty and training.

STUDY DESIGN

Blinded clinical prospective study.

ANIMALS

Twenty-five dogs undergoing surgical excision of STS.

METHODS

In vivo and ex vivo surgical margins were imaged with OCT after tumor resection. Representative images and videos were used to generate a training presentation and data sets. These were completed by 16 observers of four specialties (surgery, radiology, pathology, and OCT researchers). Images and videos from data sets were classified as cancerous or noncancerous.

RESULTS

The overall sensitivity and specificity were 88.2% and 92.8%, respectively, for in vivo tissues and 82.5% and 93.3%, respectively, for ex vivo specimens. The overall accurate classification for all specimens was 91.4% in vivo and 89.5% ex vivo. There was no difference in accuracy of interpretation of OCT imaging by observers of different specialties or experience levels.

CONCLUSION

Use of OCT to accurately assess surgical margins after STS excision was associated with a high sensitivity and specificity among various specialties. Personnel of all specialties and experience levels could effectively be trained to interpret OCT imaging.

CLINICAL SIGNIFICANCE

Optical coherence tomography can be used by personnel of different specialty experience levels and from various specialties to accurately identify canine STS in vivo and ex vivo after a short training session. These encouraging results provide evidence to justify further research to assess the ability of OCT to provide real-time assessments of surgical margins and its applicability to other neoplasms.

Determination of the lateral extent of the subcutaneous wound bed in canine cadavers after closure of skin defects to replicate tumor excision

OBJECTIVE

To determine the extent of subcutaneous involvement after primary closure of experimental skin defects.

STUDY DESIGN

Experimental study.

ANIMALS

Eight large, mixed breed dog cadavers.

METHODS

Standardized, circular skin defects with diameters of 2, 4, 6, or 8 cm were created at the lateral thorax or abdomen by using a matrix to ensure even distribution, with eight defects of each diameter. The wound beds were covered in 60% barium sulfate paste prior to primary closure. Computed tomography and a dedicated viewing program were used to measure the distance from the edge of the subcutaneous defect to the incision at set intervals along the incision.

RESULTS

The mean ± SD maximum lateral extension was 6.4 ± 1.9, 14.1 ± 4.9, 18.5 ± 6.9, and 26.0 ± 9.6 mm for 2-, 4-, 6-, and 8-cm defects, respectively. Extension >2 cm from the incision occurred in zero of eight, one of eight, five of eight, and six of eight defects after closure of 2-, 4-, 6-, and 8-cm defects, respectively. Extension >3 cm from the incision occurred in zero of eight, zero of eight, two of eight, and five of eight defects after closure of 2-, 4-, 6-, and 8-cm defects, respectively.

CONCLUSION

The lateral extent of the subcutaneous wound bed extended past previously recommended revision margins of 2 to 3 cm in some defects measuring greater than 4 cm in diameter.

CLINICAL SIGNIFICANCE

Surgeons and radiation oncologists should consider the potential extent of the subcutaneous defect when planning revision therapy, especially after large resections.

Emerging therapeutic approaches for canine sarcomas: Pushing the boundaries beyond the conventional

Sarcomas represent a group of genomically chaotic, highly heterogenous tumours of mesenchymal origin with variable mutational load. Conventional therapy with surgery and radiation therapy is effective for managing small, low-grade sarcomas and remains the standard therapeutic approach. For advanced, high-grade, recurrent, or metastatic sarcomas, systemic chemotherapy provides minimal benefit, therefore, there is a drive to develop novel approaches. The discovery of "Coley's toxins" in the 19th century, and their use to stimulate the immune system supported the application of unconventional therapies for the treatment of sarcomas. While promising, this initial work was abandoned and treatment paradigm and disease course of sarcomas was largely unchanged for several decades. Exciting new therapies are currently changing treatment algorithms for advanced carcinomas and melanomas, and similar approaches are being applied to advance the field of sarcoma research. Recent discoveries in subtype-specific cancer biology and the identification of distinct molecular targets have led to the development of promising targeted strategies with remarkable potential to change the landscape of sarcoma therapy in dogs. The purpose of this review article is to describe the current standard of care and limitations as well as emerging approaches for sarcoma therapy that span many of the most active paradigms in oncologic research, including immunotherapies, checkpoint inhibitors, and drugs capable of cellular metabolic reprogramming.

Significant advances in veterinary oncology - 60 years on

The first edition of the Journal of Small Animal Practice published in February 1960, contained a paper entitled "Recent Treatments of Malignant Neoplasia" by Dr Larry Owen. Now we have reached the 60th anniversary of JSAP, that article provides a baseline from which to review subsequent advances in veterinary oncology, which now includes worldwide networks that have resulted in veterinary oncology becoming the multidisciplinary speciality that it is today. There certainly have been many advances in understanding of the pathology and epidemiology of animal cancers and in methods of diagnosis and treatment. However, the subject has become so large and diverse that not all aspects can be covered in detail here. It should also be acknowledged that there are still many gaps in knowledge in this field and that, because of a lack of randomised clinical trials, the evidence base for what is often regarded as "standard of care" is weak.

Soft tissue sarcoma in dogs: A treatment review and a novel approach using electrochemotherapy in a case series

Canine soft tissue sarcomas (STSs) are locally invasive mesenchymal neoplasms. Electrochemotherapy (ECT) is an antitumour local ablative treatment that uses electric pulses to enhance the intracellular delivery of cytotoxic drugs. The aim of this retrospective study was to review the current treatment for STSs and to evaluate the efficacy and safety of ECT with bleomycin in canine STSs. Fifty-two dogs with 54 STSs were included. Three groups were arranged: (a) ECT alone, (b) intra-operative ECT and (c) adjuvant ECT. Signalment, tumour size, location, histological grade and margins and ECT parameters were collected. Recurrence rate (RR) and disease-free interval (DFI) were calculated. Treatment toxicity was assessed using a 6-point scale. STSs were mostly located on limbs (77.8%). Median tumour size was 4.3 cm (range 0.4-17.0 cm). Most STSs were grade I (47.7%) and II (50.0%), and histological margins were incomplete in 94.5% of cases. Two complete remissions, one partial remission and one stable disease were recorded in group 1. Group 2 and 3 were similar for tumour location, size and grade, histological margins, treatment toxicity, pulse frequency and voltage. Moreover, RR and DFI were similar between group 2 and 3 (23% and 25%, 81.5 and 243 days, respectively). Local toxicity post ECT was mild (score ≤ 2) in 66.7% of cases. Higher toxicity score was associated with higher pulse voltage (1200 vs 1000 V/cm) (P = 0.0473). ECT coupled with bleomycin resulted safe and efficient in tumour local control and should be considered as an option for treatment of canine STSs.

Adjuvant electrochemotherapy with bleomycin and cisplatin combination for canine soft tissue sarcomas: A study of 30 cases

Electrochemotherapy (ECT) couples the administration of anticancer drugs with the delivery of electric pulses that increase the drug uptake through the cell membranes, thus resulting in an improved efficacy. This study has evaluated the tolerability and efficacy of the combination of systemic bleomycin and local cisplatin as ECT agents for incompletely excised canine soft tissue sarcoma (STS). Thirty dogs with incompletely excised STSs were enrolled. The dogs received intravenous 20 mg/m² bleomycin, and the tumor bed and margins were infiltrated with cisplatin at the dose of 0.5 mg/cm². Then, trains of permeabilizing biphasic electric pulses were applied under sedation. More precisely, 5 min after the injection of the chemotherapy agents, sequences of eight biphasic pulses lasting 50 + 50 μsec each, were delivered in bursts of 1,300 V/cm using caliper electrodes. A second session was performed 2 wk later. The treatment was well tolerated and side effects were minimal. Twenty-six dogs had no evidence of recurrence at the time of manuscript writing; four had recurrence and one of the four recurring dogs died of lung metastases. Median estimated disease free was 857 d. Perivascular wall tumors response was compared to that of the other STSs, but the difference in outcome was not significant. ECT using combination of bleomycin and cisplatin appears to be effective in the treatment of incompletely resected STSs in dogs. This therapeutic approach could be a useful addition to the current options in consideration of its low cost, limited toxicity, and ease of administration.

Intra-operative imaging of surgical margins of canine soft tissue sarcoma using optical coherence tomography

Optical coherence tomography (OCT) is a rapid non-invasive imaging technique that has shown high sensitivity for intra-operative surgical margin assessment in human breast cancer clinical trials. This promising technology has not been evaluated in veterinary medicine. The objective of this study was to correlate normal and abnormal histological features with OCT images for surgical margins from excised canine soft tissue sarcoma (STS) and to establish image evaluation criteria for identifying positive surgical margins. Fourteen client-owned dogs underwent surgical resection of a STS and OCT imaging of 2 to 4 areas of interest on the resected specimen were performed. Following imaging these areas were marked with surgical ink and trimmed for histopathology evaluation. Results showed that different tissue types had distinct characteristic appearances on OCT imaging. Adipose tissue exhibited a relatively low scattering and a honey-comb texture pattern. Skeletal muscle and sarcoma tissue were both dense and highly scattering. While sarcoma tissue was highly scattering, it did not have organized recognizable structure in contrast to muscle which showed clear fibre alignment patterns. In this investigation, we showed different tissue types had different and characteristic scattering and image texture appearances on OCT, which closely correlate with low-power histology images. Given the differentiation between tissue types the results support that OCT could be used to identify positive surgical margins immediately following resection of STS. Further research is needed to assess the diagnostic accuracy of this method for surgical margin assessment.

Inter- and intra-rater reliability and agreement in determining subcutaneous tumour margins in dogs

The objective of this prospective study was to evaluate agreement and reliability of calliper-based measurements of locally invasive subcutaneous malignant tumours in dogs. Four raters measured the longest diameter of 12 subcutaneous tumours (7 soft tissue sarcomas and 5 mast cell tumours) from 11 client-owned dogs during 3 randomized, blinded measurement trials, both pre- and post-sedation. Inter- and intra-rater reliability was evaluated using intra-class correlation coefficient (ICC) and agreement was evaluated using Bland-Altman plots. Inter- and intra-rater reliability was good (ICC range of 0.8694-0.89520) and excellent (ICC range of 0.9720-0.9966), respectively. For agreement calculations, an a priori clinically relevant limit of agreement of 10 mm was set. Inter- and intra-rater agreement was unacceptable with inter-rater limits of agreement ranging from 15.9 to 55.6 mm and intra-rater limit of agreement ranging from 11.9 to 28.1 mm. Review of the measurement trial photographs revealed that calliper orientation changes were frequent, occurring in 9/12 (75%) and 8/12 (67%) pre- and post-sedation cases. No significant correlation was found between inter-rater measurement standard deviations and calliper orientation changes or dog body condition score. These findings suggest veterinarians may have poor agreement in determining the gross edge of tumours, which is expected to introduce bias and inconsistency in tumour staging, assessing response to therapy, and surgical margin planning. Due to the potential consequences for veterinary cancer patients, future studies are needed to validate the present findings.

Unclassified sarcomas: a study to improve classification in a cohort of Golden Retriever dogs

Morphologically, canine soft-tissue sarcomas (STSs) resemble human STSs. In humans, proper classification of STSs is considered essential to improve insight in the biology of these tumors, and to optimize diagnosis and therapy. To date, there is a paucity of data published on the significance of detailed classification of STSs in the dog. We revised a cohort (n = 110) of proliferative lesions obtained from a study in Golden Retrievers that were considered "soft tissue sarcoma, not otherwise specified or of uncertain subtype" in order to optimize the diagnoses of these lesions. The criteria according to the veterinary WHO classification, recent veterinary literature, and the WHO classification for humans were applied. Revision was initially based on morphologic characteristics of hematoxylin and eosin-stained histologic sections of the neoplasms. If considered necessary (n = 76), additional immunohistochemistry was applied to aid characterization. The diagnosis of STS was confirmed in 75 neoplasms (68%). Of this group, diagnosis of a specific subtype of the STSs was possible in 58 neoplasms. Seven neoplasms had morphologic characteristics that were suggestive for sarcoma subtypes only described in the WHO classification for humans. Seventeen neoplasms remained "unclassified STSs." Thirty-one lesions (28%) were diagnosed "neoplasm, not being STS." Four lesions (4%) were considered nonneoplastic. Because incorrect classification of a tumor could lead to inappropriate therapeutic intervention and prognostication, the results of our study clearly illustrate the importance of revision and further diagnosis of "unclassified STSs" in dogs.

Soft tissue sarcoma in the dog - part 1: a current review

Soft tissue sarcomas are derived from tissues of mesenchymal origin. Although local recurrence following surgical resection is the characteristic challenge in their management, 40% dogs with high-grade tumours may also develop metastatic disease, despite successful local control. Soft tissue sarcoma is a complex disease and there are many uncertainties regarding the biology and optimal clinical management. There are currently no diagnostic tests that can reliably predict the amount of surgical margin required for a particular tumour, so there can be a mismatch between treatment and disease. Historically, the tendency has been to always recommend wide excision margins but this is not fully supported by recent evidence. A selection bias for less aggressive soft tissue sarcomas in primary care practice can account for good outcomes that are achieved despite narrow surgical excision margins. On the other hand, inappropriately conservative treatment will adversely affect outcomes for patients with more aggressive disease. This review provides an update on the current understanding of management of canine soft tissue sarcomas.

HYPOFRACTIONATED RADIOTHERAPY FOR MACROSCOPIC CANINE SOFT TISSUE SARCOMA: A RETROSPECTIVE STUDY OF 50 CASES TREATED WITH A 5 × 6 GY PROTOCOL WITH OR WITHOUT METRONOMIC CHEMOTHERAPY

Wide surgical resection or a marginal/incomplete resection followed by full-course radiation therapy is the current standard of care for canine soft tissue sarcoma. The purpose of this retrospective, descriptive, bi-institutional study was to determine the effectiveness and toxicity of a hypofractionated 5 × 6 Gy protocol on macroscopic canine soft tissue sarcoma in terms of progression-free interval (PFI) and overall survival (OS), and to identify prognostic factors for patient outcome. Dogs with macroscopic soft tissue sarcoma irradiated with 5 × 6 Gy were eligible for the study. Progression-free interval and OS were compared with respect to different tumor and patient characteristics by the Kaplan-Meier method and multivariable Cox regression analysis. Fifty dogs with macroscopic disease were included. All dogs received the same radiation therapy protocol; part of the group (n = 20) received postradiation metronomic chemotherapy. Median PFI for all cases was 419 days (95% confidence interval (CI): 287-551) and median OS was 513 days (95% CI: 368-658). Dogs with tumors on the limbs had significantly longer PFI and OS, compared with head or trunk. Increasing tumor burden decreased OS. The addition of metronomic chemotherapy yielded a significantly longer OS (757 days (95% CI: 570-944) compared with dogs that did not receive systemic treatment (286 days (95% CI: 0-518), (P = 0.023)), but did not influence progression-free interval. Toxicity was low throughout all treatments. The 5 × 6 Gy radiation therapy protocol was well tolerated and provided long PFI and OS in dogs with macroscopic soft tissue sarcoma.

Canine Perivascular Wall Tumors

Canine perivascular wall tumors (cPWTs) arise from vascular mural cells and are included among soft tissue sarcomas (STSs). Most prognostic studies are performed on canine STSs as a general group and regardless of their specific histotype. The aim of this study was to identify pathological parameters and profiles with prognostic impact for cutaneous/subcutaneous cPWTs. Anatomical location, type of growth, surgical margins, and size and depth of the tumor were collected in 56 cPWTs. The association between each pair of variables was evaluated by χ2 test. Multiple correspondence analysis (MCA) was performed to describe the multivariate association of variables and was followed by cluster analysis to identify specific pathological profiles. The prognostic impact of variables and profiles was assessed by Cox regression model. Size and depth were significantly associated with increased relapse probability. Cases with complete surgical margins did not recur. Other single variables were not significantly associated with relapse. Cluster analysis on MCA considering site, depth, margins, and type of growth identified 3 pathological profiles associated with PWT relapse and having a high prognostic impact. Major prognostic factors for cPWTs were tumor size, depth of growth, and pathological profiles.

An immunohistochemical study of the expression of the hypoxia markers Glut-1 and Ca-IX in canine sarcomas

Tumor hypoxia has been associated with increased malignancy, likelihood of metastasis, and increased resistance to radiotherapy and chemotherapy in human medicine. Hypoxia-inducible factor-1 (HIF-1) is a key transcription factor that is induced by tumor hypoxia and regulates the pathways involved in cellular response and adaptation to the hostile tumor microenvironment. HIF-1 induces transcription of different proteins, including Ca-IX and Glut-1, which are considered endogenous markers of chronic hypoxia in solid tumors in humans. In this study, sections from 40 canine sarcomas (20 histiocytic sarcomas and 20 low-grade soft-tissue sarcomas) were immunostained for these markers. Expression of Glut-1 was scored based on percentage of positive staining cells (0 = <1%; 1 = 1%-50%; 2 = >50%) and intensity of cellular staining (1 = weak; 2 = strong); Ca-IX was scored based on percentage of positive cells (0 = <1%; 1 = 1%-30%; 2 = >30%). Intratumoral microvessel density was measured using CD31 to assess intratumoral neoangiogenesis. Histiocytic sarcomas showed statistically significant higher Glut-1 immunoreactivity and angiogenesis than did low-grade soft-tissue sarcomas. Intratumoral microvessel density in histiocytic sarcomas was positively associated with Glut-1 immunoreactivity score. These findings suggest a potential role of hypoxia in the biology of these tumors and may provide a base for investigation of the potential prognostic use of these markers in naturally occurring canine tumors.