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.

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.

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

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

Computed tomographic dimensions of the normal adult equine eye.

There are limited data on whether the dimensions of the equine eye and its internal structures change with bodyweight in horses. The aim of this study was to identify whether the size of the equine eye and its individual structures varied in a predictable manner with bodyweight, and to examine the reliability of computed tomography (CT) scans in the measurement of the equine eye. Ninety horses which had undergone CT examination of the head for non-ocular disease were included. All measurements of the eye were performed twice on all eyes by the same operator to quantify intra-operator agreement, and in 10 cases were also performed by a second operator to quantify inter-operator agreement. Agreement was excellent for all but the rostrocaudal measurement of the anterior chamber, which was fair. The following variables correlated significantly with bodyweight: anterior-posterior size of the globe (correlation coefficient: 0.586) and posterior segment (correlation coefficient: 0.554); the latero-medial size of the globe (correlation coefficient: 0.452), anterior chamber (correlation coefficient: 0.504) and posterior segment (correlation coefficient: 0.455); and the orbital fossa diameter (correlation coefficient: 0.219). The lens size and anterior-posterior distance of the anterior chamber did not correlate significantly with bodyweight. These results suggest that overall eye size and the size of the orbital fossa change with the bodyweight of the horse, but lens size remains consistent, and that CT measurements of the internal structures of the eye are repeatable and reproducible. This information aids in interventional procedures for ocular pathology and assessment of normal anatomy.

Canine meningiomas treated with three-dimensional conformal radiation therapy require magnetic resonance imaging to avoid a geographic miss.

Exact target volume definition is an essential prerequisite for modern radiotherapy treatment planning. Contouring the gross tumor volume of brain tumors on computed tomography (CT) images coregistered with magnetic resonance images is standard practice in human medicine. In this retrospective study, including only cases with an imaging diagnosis of meningioma, we hypothesized that the gross tumor volume contoured from the contrast-enhanced magnetic resonance imaging (MRI) (gross tumor volume-MRI) is larger when compared to the gross tumor volume contoured using contrast-enhanced CT (gross tumor volume-CT). A total of 22 dogs were included in the study. Interestingly, there was a significant statistical difference between the gross tumor volume-CT and the gross tumor volume-MRI (P = 0.001). The gross tumor volume-MRI was larger than the gross tumor volume-CT in all, but two cases. The mean ratio between gross tumor volume-MRI and gross tumor volume-CT was 1.43 (range 0.84-4.00). The mean overlap between gross tumor volume-CT and gross tumor volume-MRI was 68% (range 22-86%), while a mean of 26% of the composite gross tumor volume was defined only by MRI (range 4-76%) and a mean of 6% only by CT (range 0-22%). These findings suggest that CT and MRI are complementary modalities in radiation planning of meningiomas and their composite volume should be used to avoid geographical miss of neoplastic tissue. When the MRI is not available for planning, a margin of 0.3 cm around the gross tumor volume-CT could reduce the probability of a geographical miss. However, such numerical correction cannot be applied to the clinical practice until it is validated in a properly designed treatment planning study.

Prognostic Significance of Canine Mammary Tumor Histologic Subtypes: An Observational Cohort Study of 229 Cases.

Histopathology is considered the gold standard diagnostic method for canine mammary tumors. In 2011, a new histologic classification for canine mammary tumors was proposed. The present study was a 2-year prospective study that validated the 2011 classification as an independent prognostic indicator with multivariate analysis in a population of 229 female dogs, identifying subtype-specific median survival times (MST) and local recurrence/distant metastasis rates. Dogs with benign tumors and carcinoma arising in benign mixed tumors all had an excellent prognosis. Dogs with complex carcinoma and simple tubular carcinoma also experienced prolonged survival. Those with simple tubulopapillary carcinoma, intraductal papillary carcinoma, and carcinoma and malignant myoepithelioma had a more than 10-fold higher risk of tumor-related death. The prognosis was even worse for adenosquamous carcinoma (MST = 18 months), comedocarcinoma (MST = 14 months), and solid carcinoma (MST = 8 months). The most unfavorable outcome was for anaplastic carcinoma (MST = 3 months) and carcinosarcoma (MST = 3 months), which also had the highest metastatic rates (89% and 100%, respectively). Adenosquamous carcinoma exhibited the highest local recurrence rate (50%). In the same canine population, the tumor diameter was recognized as a strong predictor of local recurrence/distant metastasis and an independent prognosticator of survival in the multivariate analysis. Excision margins were predictive only of local recurrence, whereas lymphatic invasion and histologic grade were predictive of local recurrence/distant metastasis and survival, although only in univariate analyses. In conclusion, this study validated the 2011 classification scheme and provided information to be used in the clinical setting and as the basis for future prognostic studies.

A NOVEL, REMOVABLE, CERROBEND, BEAM-BLOCKING DEVICE FOR RADIATION THERAPY OF THE CANINE HEAD AND NECK: PILOT STUDY.

Radiation therapy of the head and neck can result in mucositis and other acute affects in the oral cavity. This prospective pilot study evaluated a novel, intraoral, beam-blocking device for use during imaging and therapeutic procedures. The beam-blocking device was made from a metal alloy inserted into a coated frozen dessert mold (Popsicle® Mold, Cost Plus World Market, Oakland, CA). The device was designed so that it could be inserted into an outer shell, which in turn allowed it to be placed or removed depending on the need due to beam configuration. A Farmer type ionization chamber and virtual water phantom were used to assess effects of field size on transmission. Six large breed cadaver dogs, donated by the owner after death, were recruited for the study. Delivered dose at the dorsal and ventral surfaces of the device, with and without the alloy block in place, were measured using radiochromic film. It was determined that transmission was field size dependent with larger field sizes leading to decreased attenuation of the beam, likely secondary to scatter. The mean and median transmission on the ventral surface without the beam-blocking device was 0.94 [range 0.94-0.96]. The mean and median transmission with the beam-blocking device was 0.52 [range 0.50-0.57]. The mean and median increase in dose due to backscatter on the dorsal surface of the beam-blocking device was 0.04 [range 0.02-0.04]. Findings indicated that this novel device can help attenuate radiation dose ventral to the block in dogs, with minimal backscatter.

Tonsillar carcinoma in dogs: Treatment outcome and potential prognostic factors in 123 cases.

BACKGROUND: Tonsillar carcinomas are rarely reported in dogs. Information on outcome after treatment is sparse and prognosis is guarded to poor. HYPOTHESIS/OBJECTIVES: Assess treatment outcome and potential prognostic factors in a population of dogs with cytological or histopathological diagnosis of tonsillar carcinoma. ANIMALS: A total of 123 client-owned dogs with diagnosis of tonsillar carcinoma confirmed by cytology or histopathology. METHODS: Retrospective, multi-institutional study. Medical records of 12 institutions were reviewed from 2012 to 2021. RESULTS: Treatment included surgery, chemotherapy (conventional, tyrosine kinase inhibitors or metronomic chemotherapy), radiotherapy, nonsteroidal anti-inflammatory drugs (NSAIDs) or a combination of these. Surgery was performed in 68 cases, chemotherapy was administered in association with NSAIDs in 64 cases, NSAIDs were used alone in 14 cases and in association with surgery in 21 cases, whereas radiotherapy was used alone or in combination with surgery or chemotherapy in 20 cases. Overall survival time (OST) was 126 days (95% confidence interval [CI], 88-164). Significantly longer survival (P < .001) was seen in dogs without evidence of metastatic disease (median survival time, 381 days; 95% CI, 116-646). Other significant positive prognostic factors included absence of clinicals signs at presentation, surgery (tonsillectomy), use of adjuvant chemotherapy and use of NSAIDs. CONCLUSION AND CLINICAL IMPORTANCE: Asymptomatic dogs, those treated with surgery, those that received adjuvant chemotherapy, and those that received NSAIDs may have a better prognosis than previously expected, but overall survival remains short for dogs with tonsillar carcinoma.

Strontium 90 plesiotherapy for the treatment of eyelid squamous cell carcinoma in eight cats.

OBJECTIVES: Squamous cell carcinoma (SCC) is the most common eyelid tumour in cats. The main treatment is extensive surgery and the cosmetic outcome can be worrisome for some owners. Strontium 90 (ST-90) plesiotherapy is a therapeutic modality used for superficial tumours, including SCC. The aim of this study was to describe the use and response of feline eyelid SCC to ST-90 plesiotherapy either as single treatment or as adjuvant therapy following surgery. METHODS: A referral centre clinical database was searched for all cats diagnosed with SCC located on an eyelid. Cats treated with ST-90 plesiotherapy were included. The response to treatment was evaluated visually every 4-6 weeks until complete healing and based on response evaluation criteria in solid tumours (RECIST). Descriptive statistics of the survival were applied to the data collected. RESULTS: Eight cats treated between 2014 and 2017 met the inclusion criteria. The median age was 10.8 years. In six cases, ST-90 was used as the only treatment modality, while in two cats it was used as an adjuvant to surgery. Four cats received a single protocol and four a hypofractionated protocol. In the six cats in which ST-90 was used as the primary treatment, the response was 100%. Four cats died at a median time of 9 months (3-17 months) after ST-90 due to causes unrelated to SCC. Of the remaining four cats, three had no signs of recurrence at a median time of 34 months and one was lost to follow-up at 17 months with no signs of recurrence. CONCLUSIONS AND RELEVANCE: This small study showed that ST-90 can be used for treatment of eyelid SCC with good therapeutic and cosmetic outcomes.

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

BACKGROUND: Radiation therapy is commonly used as an adjunct to incomplete surgical excision in dogs with mast cell tumors (MCT), but the optimal dose and fractionation regimen have yet to be determined. HYPOTHESIS: We assessed outcomes (time to local recurrence, patient survival and toxicity) of a large population of dogs with MCT that received adjunctive radiation therapy. ANIMALS: Three hundred dogs with 302 MCT treated using adjunctive radiation therapy. METHODS: Retrospective observational study. Clinical records of 4 veterinary radiation centers were reviewed. RESULTS: Local recurrence rates were similar regardless of radiation protocol with 6.6% of patients developing recurrent cutaneous MCT at a median of 526 days. Local recurrence rate was similar between high and low-risk MCT. Mast cell tumor related death was reported in 19% of all dogs, with 13% of dogs with low-risk MCT dying of their disease compared to 29% of dogs with high-risk MCT. No SC MCT (SCMCT) recurred after radiation therapy and only 7% of dogs with SCMCT were reported to have died of their disease. Mild late toxicity was common in both protocols and severe late toxicity occurred in 1.9% of dogs many years after treatment. CONCLUSIONS AND CLINICAL IMPORTANCE: Our study supports the use of adjunctive radiation for the long-term control of incompletely or narrowly excised cutaneous and SCMCT in dogs. More moderate dose and fractionation protocols may be appropriate in the adjunctive treatment of low-risk MCT in dogs. Large multicenter prospective studies are required to establish the optimal dose and fractionation for MCT of different risk categories.

Response, disease-free interval and overall survival of cats with nasal planum squamous cell carcinoma treated with a fractionated vs a single-dose protocol of strontium plesiotherapy.

OBJECTIVES: The main aim of the study was to establish response, disease-free interval (DFI) and overall survival of cats with nasal planum squamous cell carcinoma (SCC) treated with Sr90 plesiotherapy. A secondary aim was to determine whether a fractionated protocol is more effective than a single-dose protocol in terms of response, DFI and overall survival. The third aim was to evaluate whether we can identify prognostic factors that influence overall survival. METHODS: This was a retrospective study that included cats with a diagnosis of nasal planum SCC treated with Sr90 plesiotherapy at a single institution. RESULTS: Seventy-four cats were included in the study. Thirty-two were treated with a fractionated protocol and 42 with a single-dose treatment. Sr90 plesiotherapy was able to induce complete response in 74% of cats with nasal planum SCC. The median DFI was 780 days (95% confidence interval [CI] 383-1177), with 17% of cats experiencing local recurrence. The overall survival for all cats was 1039 days (95% CI 55-1528). The DFI of cats treated with the fractionated Sr90 was significantly longer compared with the single-dose treatment, whereas response and overall survival were not statistically different. Other prognostic factors that influenced the overall survival were early-stage disease, absence of concurrent problems and complete response to the treatment. Acute and long-term toxicity associated with the treatment were minimal and the aesthetic outcome was pleasing in almost all cases. CONCLUSIONS AND RELEVANCE: Strontium plesiotherapy is a safe and effective treatment of nasal planum SCC in cats.

Prognostic and predictive significance of KIT protein expression and c-kit gene mutation in canine cutaneous mast cell tumours: A consensus of the Oncology-Pathology Working Group.

One of the primary objectives of the Oncology-Pathology Working Group (OPWG), a joint initiative of the Veterinary Cancer Society and the American College of Veterinary Pathologists, is for oncologists and pathologists to collaboratively generate consensus documents to standardize aspects of and provide guidelines for oncologic pathology. Consensus is established through critical review of peer-reviewed literature relevant to a subgroup's particular focus. Subsequent acceptance and approval of the document by the OPWG membership at large establishes consensus. The intent of this publication is to help educate practitioners and pathologists on the value of diagnostics related to the KIT receptor tyrosine kinase for canine cutaneous mast cell tumours and to provide a guide for the use of these tests in veterinary medicine. This document represents the opinions of the OPWG and the authors and does not constitute a formal endorsement by the American College of Veterinary Pathologists or the Veterinary Cancer Society.

Marginal resection and adjuvant strontium plesiotherapy in the management of feline eyelid malignant peripheral nerve sheath tumours: two cases.

CASE SERIES SUMMARY: Two cats with a marginally resected eyelid malignant peripheral nerve sheath tumour were treated with adjuvant strontium plesiotherapy a few weeks after surgery. The dose applied in both cases was 200 Gy to the surface, in five fractions, on a Monday-Wednesday-Friday basis. The treatment aimed to achieve a clinical margin of approximately 1 cm around the surgical scar and multiple application fields were required to cover such an area. Local recurrence was not seen in either case after 1330 and 645 days, respectively. RELEVANCE AND NOVEL INFORMATION: The majority of periocular malignant peripheral nerve sheath tumours reported in the literature recur after surgery. In the two cases described in this report the combination of surgery and adjuvant plesiotherapy has been able to provide good local control with minimal toxicity. This multimodal approach could be considered as an alternative to aggressive surgery such as enucleation or exenteration.

Clinical outcome in 19 cats with clinical and magnetic resonance imaging diagnosis of ischaemic myelopathy (2000-2011).

Previous publications on ischaemic myelopathy in cats are limited to single case reports and small case series. The overall prognosis appears poor, with 42% of cats being euthanased. In this study the clinical outcome of 19 cats with a presumptive diagnosis of ischaemic myelopathy [based on clinical and magnetic resonance imaging (MRI) findings] was evaluated retrospectively. The degree of neurological dysfunction at the time of presentation was similar to previously reported cases, ranging from ambulatory paresis to plegia with intact nociception. The most common lesion localisations (based on MRI) were to the C1-C5 (30%) and C6-T2 (30%) spinal cord segments, with the T3-L3 and L4-S1 spinal cord segments accounting for 25% and 15%, respectively. Potential inciting or predisposing causes for development of spinal infarction were identified in 12 cats, including physical exertion, trauma, general anaesthesia, renal disease, hyperthyroidism, hypertension and hypertrophic cardiomyopathy. The median time to recovery of ambulation was 3.5 days (3-19 days). Four cats (21%) were euthanased within 2 months of diagnosis. The remaining 15 (79%) cats had a favourable outcome. Follow-up ranged from 6 months to 10 years and 4 months, with a median of 3 years and 1 month. Even when plegia was present at the time of presentation, all surviving cats with long-term, owner-derived follow-up were reported to return to a normal quality of life, suggesting that the long-term prognosis for recovery from presumed ischaemic myelopathy is favourable in the majority of cats.