Making strides in veterinary pathology

 

Dr Shelley Newman of Newman Specialty VetPath, USA, has improved the diagnosis, classification, and treatment of mast cell tumours and pancreatic diseases in veterinary species and contributed to the literature by characterising many new disease processes in exotic species.

 

Read more about their work in Research Outreach

 

Read the original article: https://doi.org/10.2460/javma.20.12.0663

 

 

Transcript:

 

Hello and welcome to Research Pod! Thank you for listening and joining us today.

 

In this episode, we will be discussing the research of Dr Shelley J Newman, owner of the consulting business Newman Specialty VetPath in the US. During her career, Newman has delved into the pathology of veterinary diseases.

 

Dr Shelley J Newman is widely known for her expertise in veterinary pathology and education, but today we will spotlight her contributions to the diagnostics of canine mast cell tumours, commonly shorted to MCTs, and pancreatitis in dogs, cats, and horses. Since 2000, a large proportion of her work has been performed in conjunction with the Gastrointestinal Laboratory at Texas A&M University, and this continues today, as she is an adjunct professor there, part of the diagnostic endoscopic biopsy service team, and a committee member for a PhD student.

 

Her most cited work surrounds the pathological characterisation of canine MCTs. MCTs are one of the most common tumours affecting the skin of dogs of various ages, but with a breed predisposition for Boxers, Boston Terriers, and Weimaraners, amongst others. At diagnosis, most dogs present with a single mass. However, in 3 to 14% of cases there are multiple masses – and around 50% of these tumours are malignant, especially in older, predisposed breeds. Many factors determine prognosis, but the histological grade of the tumour is most important. Histological examination is the study of tissue under a microscope, which helps to more accurately predict the tumour’s behaviour, something cytology has not yet fully achieved.

 

During much of Newman’s career, the Patnaik grading system was the only one in use. Newman worked with Dr Patnaik for four years at the Animal Medical Center in New York during the early 2000s. The Patnaik grading system is used concurrently with the newer two-tier Kiupel grading system for histological grading and determining the prognosis of canine MCTs. The Patnaik system classifies canine MCTs into three grades based on various factors, including cellular morphology and invasiveness. Grade I is a well-differentiated MCT characterised by good long-term prognosis, which can be treated effectively by surgery. Grade II is intermediately differentiated. Grade III MCT is poorly differentiated and more likely to spread; this makes surgical control less successful.

 

Surgery is the treatment of choice for cutaneous MCTs: recommended standard excisions remove 3cm of surrounding tissue to a 1cm depth or one fascial plane deep, often further than the visible edge of the tumour. This standard is to ensure that all abnormal cells are removed. However, surgery does not guarantee that the tumour will not return. Newman’s research on 16 dogs of various breeds found that a 2cm lateral margin and a deep margin of 1cm resulted in complete removal in 91% of Grade I and Grade II MCTs, confirmed by histological staining. Her results suggested that a 3cm lateral margin removal may therefore not always be required. She concluded that further investigations into surgical margins were needed for high-grade MCTs, as using smaller margins for surgery excision could minimise complications associated with large tumour removals. Considerable follow-up studies have since been published by many researchers.

 

Although histology is the standard practice for analysis of MCTs, in the early 2000s, molecular techniques became more prevalent. Newman explored various biological markers to predict the clinical behaviour of MCTs more accurately as histological assessment does not always predict clinical outcomes. Newman used newer histological stains, including silver staining of the argyrophilic nucleolar organiser region or AgNOR for short – present in highly proliferative cells – and antibodies directed towards other highly proliferative cells caused by potentially cancer-causing proto-oncogene defects, including p53, p21, p27, and C-kit.

 

The original Patnaik grading system for MCTs did not include subcutaneous variants of MCTs. Using proliferating cell nuclear antigen, abbreviated as PCNA, and new molecular techniques, Newman was the first to characterise the pathology of subcutaneous variants of MCTs and identify the clinical outcomes. Subcutaneous variants of MCTs in dogs were observed to be less aggressive, with an intermediate histological grade and extended mean survival times. This resulted in better long-term prognoses entirely based on location within the skin. Proliferation markers, including Ki67, PCNA, AgNOR, and C-kit scores which had previously been found helpful in aiding histological diagnosis and grading of cutaneous MCTs, were positively correlated with histological grades in subcutaneous variants of MCTs. Further studies have since expanded on this group of tumours and identified enhanced diagnostic criteria.

 

Newman’s research interests also extend to the diagnosis of pancreatic diseases in various animals, but her primary focus is on dogs. Canine pancreatic disease has been difficult to diagnose due to the lack of highly specific and sensitive tests, although this has been achieved during her career. Pancreatitis is one of the most common diseases of the exocrine pancreas in dogs – and a significant cause of morbidity and mortality. The classification system of pancreatitis in dogs was last updated in 1992 and contained vague definitions of the types of pancreatitis. Chronic pancreatitis is a chronic inflammation that affects surrounding tissues and can permanently damage the pancreas leading to fibrosis, which is scarring of the tissue. Acute pancreatitis is acute inflammation which causes marked cell death and leakage of digestive enzymes into the surrounding peri-pancreatic fat, resulting in saponification or soap formation, a characteristic histologic change. The latter is also usually associated with abdominal pain.

 

Few studies reported the histological lesions of dogs with pancreatitis, and no studies until Newman’s sentinel work have evaluated the localisation of inflammation, fibrosis, and necrosis or tissue death associated with this condition in a large number of dogs. Newman sheds light on these previously unexplored factors in post-mortem studies of dogs in an attempt to create a predictable distribution of lesions. Through her research, the disease process is being better characterised, enabling improvements in the accuracy of pancreatitis diagnosis.

 

Notably, Newman showed that pancreatitis in dogs displays a random distribution of lesions. She therefore recommends that multiple sections of the pancreas be assessed for necrosis or inflammatory changes, both post-mortem and ante-mortem. Newman emphasises the need for a functional grading system for characterising pancreatitis to improve diagnosis and prognosis of the disease, as it is clear from her post-mortem studies that a single biopsy is not sufficient. The development of an improved diagnostic system for exocrine pancreatitis in dogs is now forming the basis of similar research in cats.

 

To test the sensitivity of serum markers for the diagnosis of canine pancreatitis, Newman assessed thousands of pancreatic tissue samples from dogs, something not previously extensively studied. A variety of diagnostic tests have been trialled for testing trypsin-like immunoreactivity, or TLI for short, as well as serum amylase and lipase levels, which are typically elevated in humans with acute pancreatitis. Since these ground-breaking studies, a canine pancreatic lipase immunoreactivity test, commonly known as a cPLI test, has been used more widely by veterinarians due to its increased sensitivity and specificity in the diagnosis of pancreatitis in canines. cPLI can also be used as a biomarker of damage in the pancreas and has been incorporated in survey testing for pancreatitis around the globe. Following assessment of numerous canine pancreatic samples, serum reference ranges were able to be calculated, and the test is available online as a useful aid in canine pancreatitis diagnoses utilising a blood sample.

 

However, as pathologic lesions are randomly distributed in pancreatitis in dogs, diagnosis via single biopsies is difficult. On the other hand, fine needle aspiration, or FNA, results were not well documented. Newman found that the non-invasive FNA for pancreatic sampling produced high-quality cytological samples, enabling their analysis for diagnosis. FNA prevented any significant damage to the pancreas and the development of any further complications. This was reflected by the stable cPLI levels. This technique has improved the diagnosis of pancreatitis in dogs and prevented complications or associated injury from more aggressive biopsy procedures.

 

In a landmark study that aimed to characterise the clinical and histopathological features of chronic pancreatitis in dogs, Newman found that the most frequent symptoms of this disease were vomiting, diarrhoea, and decreased appetite. She also identified that chronic pancreatitis was more common in older, non-sporting, and neutered dogs, which often had other concurrent diseases, including neurologic or liver diseases.

 

Newman has also investigated pancreatic diseases in other veterinary species, including cats and horses. Cyclooxygenase-2, or COX-II for short, is an enzyme responsible for producing prostaglandin E2, otherwise known as PGE2, and this is often overexpressed in tumorous conditions. COX-II is seen to be overexpressed in many human and canine pancreatic adenocarcinomas. COX-II inhibitors are therefore useful anti-cancer agents effective in both humans and dogs. However, COX-II expression in pancreatic adenocarcinomas was not consistently present in all pancreatic cancers expressed in cats, deeming it less useful as a prognostic marker of pancreatic adenocarcinoma for felines. This inconsistency of COX-II expression suggests that despite the low number of cases assessed, COX-II inhibitor drugs have low potential as a treatment choice for pancreatic cancers in cats – meaning other therapeutic options need to be explored.

 

In horses, pancreatic diseases are rare, but diagnosis is difficult and successful treatment options are limited. Newman found that pancreatic lesions and subsequent disease often present as colic and are frequently seen with other comorbidities, including liver, gastrointestinal, and endocrine conditions. Equine pancreatic disease was also found to be associated with parasites and grain overload. However, there is a need for further research into equine pancreatitis to gain a better understanding of how it is associated with comorbidities and how it causes death.

 

Newman has also shed light on cases of aflatoxicosis in dogs caused by food contaminated with the toxic fungus A. flavus. Although rare, she found that the 2005–2006 outbreak began with dogs exposed to contaminated dog food in specific geographical locations supplied from a common processing plant. She was able to identify aflatoxicosis in these dogs using liver metabolites, feed analysis, and microscopic evaluations.

 

Newman also has provided evidence that female pot-bellied pet pigs have an increased risk of developing uterine lesions, similar to fibroids in women, and found a link between increased age and development of these lesions. She also noted that pot-bellied pet pigs had an increased risk of reproductive and gastrointestinal issues with increased age, with malignant cancer frequently identified, especially of the liver and intestine.

 

Newman has spent many years researching diseases in veterinary animals exploring new techniques and ways in which we can better characterise poorly understood diseases to improve diagnostic techniques. This can be seen by her extensive work in characterising various types of MCTs and pancreatitis in dogs and improving their diagnostic grading system. Newman also has started to extend these findings to other animals, including horses and cats, to better understand the disease processes. Current work by a graduate student at the GI Lab at Texas A&M University is continuing this research. Newman has contributed greatly to our understanding of these diseases and has offered better substitutes for the current techniques used to diagnose certain diseases in animals.

 

That’s all for this episode – thanks for listening, and stay subscribed to Research Pod for more of the latest science. See you again soon.

 

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