Pheochromocytomas and paragangliomas in humans and dogs

Intraoperative hypertensive crisis in a dog with functional paraganglioma of the gall bladder

A 15-year-old spayed female mongrel presented with anorexia and an abdominal mass. The mass originated from the gall bladder and was surgically resected along with divisionectomy of the central hepatic division. Paroxysmal hypertension and tachycardia were noted during manipulation of the mass. Following resection, arterial blood pressure decreased significantly. Histopathological analysis confirmed a diagnosis of neuroendocrine neoplasm. Immunohistochemical staining for synaptophysin and chromogranin A yielded diffuse and strong positive results, while gastrin was positive in only 10% of the cells. The preoperative elevated concentrations of catecholamine in the urinalysis showed a marked decrease after surgery. Based on these findings, the tumour was diagnosed as a functional paraganglioma of the gall bladder. The patient has undergone regular thoracic radiographs and ultrasound examinations and, until 431 days after surgery, has shown no signs of metastases or recurrences. Based on our literature search, we report the first case of functional paraganglioma of the gall bladder in a dog.

Animal and Cell Culture Models of PPGLs - Achievements and Limitations

Research on rare tumors heavily relies on suitable models for basic and translational research. Paragangliomas (PPGL) are rare neuroendocrine tumors (NET), developing from adrenal (pheochromocytoma, PCC) or extra-adrenal (PGL) chromaffin cells, with an annual incidence of 2-8 cases per million. While most PPGL cases exhibit slow growth and are primarily treated with surgery, limited systemic treatment options are available for unresectable or metastatic tumors. Scarcity of appropriate models has hindered PPGL research, preventing the translation of omics knowledge into drug and therapy development. Human PPGL cell lines are not available, and few animal models accurately replicate the disease's genetic and phenotypic characteristics. This review provides an overview of laboratory models for PPGLs, spanning cellular, tissue, organ, and organism levels. We discuss their features, advantages, and potential contributions to diagnostics and therapeutics. Interestingly, it appears that in the PPGL field, disease models already successfully implemented in other cancers have not been fully explored.

SDHi fungicides: An example of mitotoxic pesticides targeting the succinate dehydrogenase complex

Succinate dehydrogenase inhibitors (SDHi) are fungicides used to control the proliferation of pathogenic fungi in crops. Their mode of action is based on blocking the activity of succinate dehydrogenase (SDH), a universal enzyme expressed by all species harboring mitochondria. The SDH is involved in two interconnected metabolic processes for energy production: the transfer of electrons in the mitochondrial respiratory chain and the oxidation of succinate to fumarate in the Krebs cycle. In humans, inherited SDH deficiencies may cause major pathologies including encephalopathies and cancers. The cellular and molecular mechanisms related to such genetic inactivation have been well described in neuroendocrine tumors, in which it induces an oxidative stress, a pseudohypoxic phenotype, a metabolic, epigenetic and transcriptomic remodeling, and alterations in the migration and invasion capacities of cancer cells, in connection with the accumulation of succinate, an oncometabolite, substrate of the SDH. We will discuss recent studies reporting toxic effects of SDHi in non-target organisms and their implications for risk assessment of pesticides. Recent data show that the SDH structure is highly conserved during evolution and that SDHi can inhibit SDH activity in mitochondria of non-target species, including humans. These observations suggest that SDHi are not specific inhibitors of fungal SDH. We hypothesize that SDHi could have toxic effects in other species, including humans. Moreover, the analysis of regulatory assessment reports shows that most SDHi induce tumors in animals without evidence of genotoxicity. Thus, these substances could have a non-genotoxic mechanism of carcinogenicity that still needs to be fully characterized and that could be related to SDH inhibition. The use of pesticides targeting mitochondrial enzymes encoded by tumor suppressor genes raises questions on the risk assessment framework of mitotoxic pesticides. The issue of SDHi fungicides is therefore a textbook case that highlights the urgent need for changes in regulatory assessment.

Whole transcriptome analysis of canine pheochromocytoma and paraganglioma

Pheochromocytomas and paragangliomas (PPGLs) are neuroendocrine tumors arising from the chromaffin cells in the adrenal medulla and extra-adrenal paraganglia, respectively. Local invasion, concurrent disorders, and metastases prevent surgical removal, which is the most effective treatment to date. Given the current lack of effective medical treatment, there is a need for novel therapeutic strategies. To identify druggable pathways driving PPGL development, we performed RNA sequencing on PPGLs (n = 19) and normal adrenal medullas (NAMs; n = 10) of dogs. Principal component analysis (PCA) revealed that PPGLs clearly clustered apart from NAMs. In total, 4,218 genes were differentially expressed between PPGLs and NAMs. Of these, 232 had a log2 fold change of >3 or < -3, of which 149 were upregulated in PPGLs, and 83 were downregulated. Compared with NAMs, PPGLs had increased expression of genes related to the cell cycle, tumor development, progression and metastasis, hypoxia and angiogenesis, and the Wnt signaling pathway, and decreased expression of genes related to adrenal steroidogenesis. Our data revealed several overexpressed genes that could provide targets for novel therapeutics, such as Ret Proto-Oncogene (RET), Dopamine Receptor D2 (DRD2), and Secreted Frizzled Related Protein 2 (SFRP2). Based on the PCA, PPGLs were classified into 2 groups, of which group 1 had significantly higher Ki67 scores (p = 0.035) and shorter survival times (p = 0.04) than group 2. Increased expression of 1 of the differentially expressed genes between group 1 and 2, pleiotrophin (PTN), appeared to correlate with a more aggressive tumor phenotype. This study has shed light on the transcriptomic profile of canine PPGL, yielding new insights into the pathogenesis of these tumors in dogs, and revealed potential novel targets for therapy. In addition, we identified 2 transcriptionally distinct groups of PPGLs that had significantly different survival times.

Laparoscopic vs. open adrenalectomy: perioperative data and survival analysis in 70 dogs with an adrenal tumor

Adrenalectomy is the treatment of choice in case of functional adrenal tumors and malignant adrenal incidentalomas. Laparoscopic adrenalectomy (LA) in dogs has gained popularity in recent years, however, clinical studies on large patient populations are scarce. This retrospective study describes perioperative and recurrence data, survival, and prognostic factors in 70 dogs that underwent LA or open adrenalectomy (OA) in our hospital between 2008 and 2022. Diagnosis was based on history, clinical signs, endocrine function tests and advanced diagnostic imaging. Laparoscopic adrenalectomy was performed in 42 dogs (n = 27 naturally occurring hypercortisolism, n = 4 pheochromocytoma, n = 1 pheochromocytoma with concurrent hypercortisolism, n = 10 incidentaloma) and OA in 28 dogs (n = 22 hypercortisolism, n = 3 pheochromocytoma, n = 3 incidentaloma). Bilateral adrenalectomy was performed in 8/70 dogs. Surgical duration of LA and OA did not differ significantly in unilateral and bilateral procedures (P = 0.108 and P = 0.101, respectively). Systemic hypertension occurred in 7/41 and 1/28 dogs during LA and OA, respectively (P = 0.130). Hypotension occurred in 2/41 and 4/28 dogs during LA and OA, respectively (P = 0.214). A total of 40/42 dogs in the LA group and 27/28 in the OA group survived to discharge (P = 0.810). Mean hospital stay was significantly shorter (P = 0.006) after LA (1.5 days, range 1-3) than after OA (2.2 days, range 1-4). No significant differences were demonstrated between LA and OA groups in recurrence of adrenal-dependent endocrine disease (P = 0.332), disease-free period (P = 0.733) and survival time (P = 0.353). The disease-specific 1-, 2- and 3-year survival rates were 95, 89, and 89% after LA and 92, 88, and 81% after OA. Tumor size was significantly associated with the occurrence of a recurrence. In addition, tumor size had a negative effect on the disease-free period and survival time. This study shows a favorable outcome of both LA and OA in dogs. Based on low perioperative complication rate, short hospitalization time and long-term outcomes comparable to OA in selected cases, the less invasive laparoscopic approach is considered the preferred technique.

Phaeochromocytoma associated with cardiomyopathy and leukocytoclastic vasculitis in a dog

Phaeochromocytomas are rare tumours of the adrenal medulla that can be associated with various presentations. Many of the better characterized clinical signs, including weakness, tachycardia and tachypnoea, are attributable to excessive and unregulated catecholamine secretion from functional tumours. In addition to catecholamine-induced cardiomyopathy and vasospasm, the invasive nature of phaeochromocytomas can lead to occlusion of the caudal vena cava contributing to systemic cardiovascular compromise. In humans, leukocytoclastic vasculitis is a rarely reported manifestation of catecholamine excess associated with phaeochromocytomas. We now describe a dog that had an invasive unilateral phaeochromocytoma with histological evidence of myocardial damage, consistent with catecholamine-induced cardiomyopathy, and leukocytoclastic vasculitis of small vessels in a range of tissues. We conclude that catecholamine excess may have played a role in the pathogenesis of vasculitis in this case. To the best of our knowledge, this is the first documented association between phaeochromocytoma and leukocytoclastic vasculitis in a non-human species.

Diagnosis, treatment and outcome of pheochromocytoma in a cat

Pheochromocytoma in cats is a rare clinical condition characterised by the development of a secretory endocrine tumour that arises from the adrenal medulla. An 8-year-old castrated male, domestic shorthair cat was referred for further investigation of a 4-month history of progressive weight loss with normal appetite, polyuria/polydipsia, generalised weakness, and severe hypertension. Sonography and computed tomography of the abdomen disclosed a mass arising from the left adrenal gland. The contralateral adrenal gland was normal in size and shape. Results from a low dose dexamethasone suppression test and measurements of plasma aldosterone concentration and plasma renin activity ruled out a cortisol-secreting tumour and aldosteronoma. The clinical presentation made a sex-steroid secreting tumour unlikely. Increased plasma metanephrine and normetanephrine concentrations prioritised the differential diagnosis of pheochromocytoma. The cat underwent adrenalectomy of the left gland and histopathological diagnosis with immunohistochemical markers confirmed the diagnosis.

Stereotactic body radiation therapy as an alternative to adrenalectomy for the treatment of pheochromocytomas in 8 dogs

The objective of this report is to describe the use and outcome of stereotactic body radiation therapy (SBRT) for treatment of pheochromocytomas in 8 dogs. Pheochromocytomas are an uncommon but challenging tumour to manage. Adrenalectomy is the standard of care for treatment of pheochromocytomas in both animals and humans; however, unpredictable catecholamine secretion from the tumour and vascular and local invasion of the tumour and thrombi can pose life-threatening perioperative and anaesthetic risks. SBRT has been investigated as an alternative to adrenalectomy in human patients with pheochromocytomas. Eight dogs with clinical signs, an adrenal mass, and cytology and/or urine normetanephrine/creatinine ratios consistent with pheochromocytoma were treated with SBRT in lieu of adrenalectomy. Three dogs presented with acute hemoabdomen. Seven dogs had caval tumour invasion, 3 with extension into the right atrium. Following SBRT, all dogs had complete resolution of clinical signs and reduced urine normetanephrine/creatinine ratio and/or tumour size. No significant anaesthetic complications were encountered. Acute radiation toxicity was limited to grade I gastrointestinal signs in 3 dogs and resolved within 1-2 days of symptomatic therapy. Five of 8 dogs were alive at the time of follow up, with a median follow up time of 25.8 months. SBRT resulted in a favourable outcome and mitigated the life-threatening risks of adrenalectomy in these 8 dogs. SBRT may be a safe and effective alternative to adrenalectomy for pheochromocytomas in dogs with non-resectable tumours, or for owners averse to the risks of surgery.

Short- and long-term survival after adrenalectomy in 53 dogs with pheochromocytomas with or without alpha-blocker therapy

OBJECTIVE

To report data related to the short- and long-term survival of dogs undergoing adrenalectomy for pheochromocytoma, and to determine the influence of preoperative alpha-blocker therapy.

STUDY DESIGN

Retrospective.

ANIMALS

Fifty-three dogs.

METHODS

Medical records were reviewed for dogs diagnosed with pheochromocytoma and treated with adrenalectomy between 2010 and 2020. Preoperative management, imaging studies, intraoperative cardiovascular instability, complications, and procedural information were recorded. When applicable, duration of survival and cause of death, time to recurrence or metastasis, and postoperative complications were recorded.

RESULTS

During anesthesia, a hypertensive episode was documented in 46/53 dogs and arrhythmias were recorded in 16/53 dogs. Of these, 37/46 hypertensive dogs and 11/16 dogs with arrhythmias were treated with an alpha-blocker before surgery. Intraoperative systolic blood pressures reached higher levels by a magnitude of nearly 20% in dogs that were treated preoperatively with an alpha-blocker (P = .01). All dogs survived surgery and 44 survived to discharge. Follow up ranged from 6 to 1653 days (median 450 days). Median survival time for dogs discharged from the hospital was 1169 days (3.2 years). Recurrence and metastasis were suspected in 3 and 8 dogs, respectively.

CONCLUSION

Most dogs survived the immediate postoperative period and achieved long-term survival with a low reported incidence of tumor recurrence or metastasis. Preoperative alpha-blocker therapy was not associated with increased survival.

CLINICAL SIGNIFICANCE

The favorable outcomes reported in this study should be taken into consideration when discussing treatment options for dogs with pheochromocytomas. This study provides no evidence to support preoperative alpha-blocker therapy.

Imaging features of retroperitoneal extra-adrenal paragangliomas in 10 dogs

Retroperitoneal paragangliomas are rare tumors of the neuroendocrine system. Only a few canine case reports are available with rare descriptions of their imaging features. The objectives of this multi‐center, retrospective case series study were to describe the diagnostic imaging features of confirmed retroperitoneal paragangliomas and specify their location. Medical records and imaging studies of 10 affected dogs with cytological or histopathologic results concordant with retroperitoneal paragangliomas were evaluated. Dogs had a median age of 9 years. Four of them had clinical signs and laboratory reports compatible with excessive production of catecholamines. Six ultrasound, four CT, four radiographic, and one MRI studies were included. The paragangliomas did not have a specific location along the aorta. They were of various sizes (median 33 mm, range: 9–85 mm of length). Masses had heterogeneous parenchyma in six of 10 dogs, regardless of the imaging modality. Strong contrast enhancement was found in all CT studies. Encircling of at least one vessel was detected in six of 10 masses, clear invasion of a vessel was identified in one of 10 masses. In five of 10 cases, the masses were initially misconstrued as lymph nodes by the on‐site radiologist. Retroperitoneal paragangliomas appear along the abdominal aorta, often presenting heterogeneous parenchyma, possibly affecting the local vasculature, and displaying strong contrast enhancement on CT. Clinical signs can be secondary to mass effects or excessive catecholamine production. Underdiagnosis and misdiagnosis of this tumor are suspected as they can be silent, of small size, or confused with other structures.

18F-FDG PET/CT image findings of a dog with adrenocortical carcinoma

Background

In human medicine, 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) has been used to differentiate between benign and malignant adrenal tumors and to identify metastases. However, canine adrenocortical carcinomas identified by 18F-FDG PET/computed tomography (CT) have not been reported.

Case presentation

A 13-year-old, castrated male, Cocker Spaniel dog with severe systolic hypertension exhibited an adrenal mass approximately 3.6 cm in diameter on ultrasonography. There was no evidence of pulmonary metastasis or vascular invasion on thoracic radiography and abdominal ultrasonography, respectively. 18F-FDG PET/CT was performed to identify the characteristics of the adrenal mass and the state of metastasis. One hour after injection of 5.46 MBq/kg 18F-FDG intravenously, the peripheral region of the adrenal mass visually revealed an increased 18F-FDG uptake, which was higher than that of the liver, and the central region of the mass exhibited necrosis. The maximal standardized uptake value (SUV) of the adrenal mass was 3.24; and relative SUV, calculated by dividing the maximal SUV of the adrenal tumor by the mean SUV of the normal liver, was 5.23. Adrenocortical carcinoma was tentatively diagnosed and surgical adrenalectomy was performed. Histopathologic examination of the resected adrenal mass revealed the characteristics of an adrenocortical carcinoma. After adrenalectomy, systolic blood pressure reduced to below 150 mmHg without any medication.

Conclusion

This is the first case report of 18F-FDG PET/CT findings in a dog with suspected adrenocortical carcinoma and may provide valuable diagnostic information for adrenocortical carcinoma in dogs.

Model systems in SDHx-related pheochromocytoma/paraganglioma

Pheochromocytoma (PHEO) and paraganglioma (PGL) (together PPGL) are tumors with poor outcomes that arise from neuroendocrine cells in the adrenal gland, and sympathetic and parasympathetic ganglia outside the adrenal gland, respectively. Many follow germline mutations in genes coding for subunits of succinate dehydrogenase (SDH), a tetrameric enzyme in the tricarboxylic acid (TCA) cycle that both converts succinate to fumarate and participates in electron transport. Germline SDH subunit B (SDHB) mutations have a high metastatic potential. Herein, we review the spectrum of model organisms that have contributed hugely to our understanding of SDH dysfunction. In Saccharomyces cerevisiae (yeast), succinate accumulation inhibits alpha-ketoglutarate-dependent dioxygenase enzymes leading to DNA demethylation. In the worm Caenorhabditis elegans, mutated SDH creates developmental abnormalities, metabolic rewiring, an energy deficit and oxygen hypersensitivity (the latter is also found in Drosophila melanogaster). In the zebrafish Danio rerio, sdhb mutants display a shorter lifespan with defective energy metabolism. Recently, SDHB-deficient pheochromocytoma has been cultivated in xenografts and has generated cell lines, which can be traced back to a heterozygous SDHB-deficient rat. We propose that a combination of such models can be efficiently and effectively used in both pathophysiological studies and drug-screening projects in order to find novel strategies in PPGL treatment.

Laparoscopic resection of retroperitoneal paraganglioma close to caudal vena cava in a dog

OBJECTIVE

To report laparoscopic resection of retroperitoneal paraganglioma close to the caudal vena cava in a dog.

STUDY DESIGN

Case report.

ANIMAL

Twelve-year-old, neutered male Jack Russell terrier.

METHODS

The dog had undergone three previous cystotomies for bladder stones. On follow-up ultrasonographic evaluation, a 14-mm × 17-mm tumour was incidentally detected in the dorsal midline of the caudal abdomen. The dog underwent computed tomography (CT) imaging and ultrasound-guided fine needle aspiration of the tumour under general anaesthesia. CT imaging showed that the tumour was close to the caudal vena cava. There was no evidence of metastasis. Neuroendocrine tumour was suspected on cytologic examination. Based on these findings, laparoscopic tumour resection was performed using a vessel-sealing device. The operation time was 136 minutes.

RESULTS

The dog was stable after recovery from anaesthesia and discharged to home the next day. Histopathological diagnosis of the tumour was a paraganglioma. The dog remained without clinical evidence of recurrent tumour or metastasis for 670 days after the surgery.

CONCLUSION

Retroperitoneal paraganglioma in dogs is uncommon, but it is one of the differential diagnoses of a retroperitoneal tumour. Laparoscopic resection of a retroperitoneal paraganglioma was successfully performed in the dog. Laparoscopic resection conferred the advantages over open surgery of being minimally invasive, providing better visualization of the surgical field through pneumoperitoneum and semisternal patient recumbency, and allowing for magnification of the operative field, which facilitated the ease and safety of the procedure.

A First Case Report of Orbital Extra-Adrenal Paraganglioma in Cat

Paraganglioma is a rare neuroendocrine neoplasm originating from paraganglia and consisting of neuroendocrine cells of the sympathetic and parasympathetic nervous system. Extra-adrenal paraganglioma occurs with a low incidence in both humans and animals. This report presents the first case of paraganglioma in a cat with orbital primary location. An 18-year-old spayed female European domestic shorthair cat of 3.60 kg body weight was evaluated in a private veterinary clinic in Perugia, Italy, for a pronounced exophthalmos of the right eye. The cat underwent surgery for the enucleation of the right eye and of the mass. The biopsy samples of the removed tissue were fixed in 10% buffered neutral formalin for histological and immunohistochemical evaluations. Therefore, specific markers were used for immunohistochemical investigations, such as anti-neuron specific enolase (NSE), anti-synaptophysin, anti-glial fibrillary acid protein, anti-cytokeratin and anti-chromogranin. The results of these investigations allowed establishing the final diagnosis of ocular extra-adrenal paraganglioma of the cat.

Biopsy of an intracardiac paraganglioma in a dog using a fluoroscopically guided endovascular technique

A 10‐year‐old female spayed mixed breed dog was evaluated for diarrhea and vomiting. Diagnostic imaging demonstrated the presence of an intracardiac mass. A modified Seldinger technique was used to access the right jugular vein, and an endomyocardial biopsy forceps was introduced through a sheath to obtain several biopsies. Histopathology and immunohistochemistry demonstrated a paraganglioma. The dog underwent 1 fraction of radiotherapy and l‐asparaginase chemotherapy and was discharged. The dog developed a pulmonary thromboembolism 2 days after radiotherapy and chemotherapy, and the owner elected humane euthanasia. Although long‐term assessment of treatment response was unable to be performed, this novel diagnostic option could be considered for similar cases due to success in obtaining a histopathologic diagnosis, which is essential in developing a disease‐specific treatment plan. This report also describes the use of radiotherapy for primary treatment of an intracardiac neoplasm, which can be a consideration in the future.

A Multi-Institutional Retrospective Analysis of Toceranib Phosphate for Presumed or Confirmed Canine Aortic Body Chemodectomas

Aortic body tumors, specifically chemodectomas, are the second most common type of canine cardiac tumor; however, information about treatment is currently lacking. This study included dogs with a presumptive or definitive diagnosis of an aortic body chemodectoma that underwent treatment with toceranib phosphate. Cases were solicited via the American College of Veterinary Internal Medicine Cardiology, Internal Medicine, and Oncology listservs using an electronic survey. Cox multivariate analysis of factors potentially impacting survival time was completed. Twenty-seven (27) cases were included in analysis. The clinical benefit rate (complete remission, partial remission, or stable disease >10 weeks) was 89%. A median survival time of 478 days was found for those receiving toceranib alone (n = 14), which was not statistically different from those treated with additional modalities (521 days). No factors evaluated statistically impacted outcome. Further, prospective studies are warranted to evaluate the use of toceranib for the treatment of canine aortic body chemodectomas.

Urinary vanillylmandelic acid:creatinine ratio in dogs with pheochromocytoma

Pheochromocytoma diagnosis in dogs is challenging because biochemical tests are not always available. In humans, urinary vanillylmandelic acid (VMA) is part of a pheochromocytoma biochemical diagnostic profile, whereas its diagnostic accuracy is currently unknown in dogs with pheochromocytoma. Prospectively, VMA was determined by HPLC and expressed as the ratio with respect to urinary creatinine (VMA:C). The diagnostic accuracy of the VMA:C ratio was evaluated by analyzing the receiver operating characteristic (ROC) curve in 10 healthy dogs, 8 dogs with pituitary-dependent hypercortisolism, 8 dogs with adrenal-dependent hypercortisolism, and 7 dogs with pheochromocytoma. The pheochromocytoma diagnosis was confirmed by histology and immunohistochemistry in all tumors. The VMA:C ratio was significantly higher in dogs with pheochromocytoma (158 [53.4 to 230.8] × 10^-3) than in dogs with adrenal-dependent hypercortisolism (48.1 [24.3 to 144.9] × 10^-3; P < 0.05), dogs with pituitary-dependent hypercortisolism (37.5 [32 to 47.1] × 10^-3; P < 0.001), and healthy dogs (33.8 [13.3 to 87.9] × 10^-3; P < 0.001). When using a VMA:C ratio >58.2 × 10^-3 for pheochromocytoma diagnosis, a sensitivity of 85.7% and a specificity of 88.4% were obtained. Nevertheless, when using a cut-off ratio of 4 times the median VMA:C ratio determined in healthy dogs, there was no overlap (100% specificity). The area under the ROC curve indicated that the VMA:C ratio test could be used to discriminate between dogs with and without pheochromocytoma, what leads to the conclusion that it is useful for pheochromocytoma diagnosis in dogs.

Beyond tradition and convention: benefits of non-traditional model organisms in cancer research

Traditional laboratory model organisms are indispensable for cancer research and have provided insight into numerous mechanisms that contribute to cancer development and progression in humans. However, these models do have some limitations, most notably related to successful drug translation, because traditional model organisms are often short-lived, small-bodied, genetically homogeneous, often immunocompromised, are not exposed to natural environments shared with humans, and usually do not develop cancer spontaneously. We propose that assimilating information from a variety of long-lived, large, genetically diverse, and immunocompetent species that live in natural environments and do develop cancer spontaneously (or do not develop cancer at all) will lead to a more comprehensive understanding of human cancers. These non-traditional model organisms can also serve as sentinels for environmental risk factors that contribute to human cancers. Ultimately, expanding the range of animal models that can be used to study cancer will lead to improved insights into cancer development, progression and metastasis, tumor microenvironment, as well as improved therapies and diagnostics, and will consequently reduce the negative impacts of the wide variety of cancers afflicting humans overall.

Paraganglioma of the Tongue in a Chow Chow Dog: A Comparison With the Human Counterpart and Literature Review

Over the last 20 years, substantial knowledge has been developed in Veterinary oncology, and tumors previously reported only in humans have been identified in animals. Primary paragangliomas of the tongue are extremely rare tumors in human beings and have never been reported in animals. A Chow Chow dog showed an ulcerated nodule at the lingual body, deeply infiltrated, which extended to the base of the tongue. A full clinical and pathological investigation was conducted, and a post-surgical follow-up of 6 months did not detect recurrence. Cytological, histological, and immunohistochemical features are presented and support the diagnosis of lingual paraganglioma. The paraganglioma of the tongue reported in this Chow Chow dog shares many similarities with the human counterpart.

Favorable outcome of pheochromocytoma in a dog with atypical Cushing's syndrome and diabetes mellitus following medical treatment: a case report

Background

Pheochromocytoma (PCC) has poor prognosis and adrenalectomy is hard to be performed, in case of caudal vena cava invasion. The long-term administration of phenoxybenzamine in PCC has not been reported in dogs.

Case presentation

A 14-year-old castrated male Poodle dog presented with an abdominal mass. On physical examination, hypertension, increased lens opacity, calcinosis cutis, generalized alopecia, and systolic murmur were observed. Serum chemistry and urinalysis profiles revealed hyperglycemia, hypercholesterolemia, elevated liver enzymes, and glucosuria. Abdominal ultrasonography showed a right adrenal mass with invasion of the caudal vena cava, which was cytologically diagnosed as suspected PCC. An adrenal mass (width × height × length, 28 × 26 × 48 mm³) was found on computed tomography and diagnosed as PCC with increased plasma metanephrines and normetanephrines. An adrenocorticotropin hormone stimulation test showed elevated adrenal hormones (androstenedione, estradiol, progesterone, and 17-OH progesterone) with normal cortisol, compatible with atypical Cushing’s syndrome. The dog was managed with trilostane, phenoxybenzamine, and insulin therapy. Glycosylated hemoglobin and fructosamine levels gradually decreased, and hypertension resolved. In the 10-month follow-up period, the liver enzymes levels gradually decreased, and the clinical signs of the dog were well-controlled without deterioration.

Conclusions

This case report describes long-term medical management without adrenalectomy of PCC complicated with atypical Cushing’s syndrome and DM.

Surgical Excision of an Adrenal Neuroblastoma in a Dog

A 11-month-old, intact male, Rhodesian Ridgeback was presented to the Veterinary Teaching Hospital with signs of inappetence, lethargy, and abdominal pain for 3 days. A large and well-defined abdominal retroperitoneal mass, related with the left kidney, at the expected location of the adrenal gland, was revealed by radiography, ultrasound, and computed tomography. The mass extended caudally to the iliac artery bifurcation, compressing the aorta, caudal vena cava, and both kidneys. Cytology findings were compatible with a malignant round cell tumor. The most probable diagnosis was neuroblastoma. Following a comprehensive discussion with the owners about a treatment plan, surgical excision was performed. Because a wide excision would compromise major vessels, excision was performed after careful dissection of the aorta and vena cava. The left kidney was removed because the proximal ureter could not be separated from the tumor. The animal recovered successfully. Diagnosis was confirmed by histopathology and immunohistochemistry, but the owners decided not to pursue any further treatment. Clinical signs of abdominal pain recurred within 1 month following surgery. Therefore, the animal was euthanized upon the owners' request. This report describes the diagnosis, surgical treatment, and follow-up of a dog with an abdominal peripheral neuroblastoma.

Molecular Alterations in Dog Pheochromocytomas and Paragangliomas

8658860258318000Recently, genetic alterations in the genes encoding succinate dehydrogenase subunit B and D (SDHB and SDHD) were identified in pet dogs that presented with spontaneously arising pheochromocytomas (PCC) and paragangliomas (PGL; together PPGL), suggesting dogs might be an interesting comparative model for the study of human PPGL. To study whether canine PPGL resembled human PPGL, we investigated a series of 50 canine PPGLs by immunohistochemistry to determine the expression of synaptophysin (SYP), tyrosine hydroxylase (TH) and succinate dehydrogenase subunit A (SDHA) and B (SDHB). In parallel, 25 canine PPGLs were screened for mutations in SDHB and SDHD by Sanger sequencing. To detect large chromosomal alterations, single nucleotide polymorphism (SNP) arrays were performed for 11 PPGLs, including cases for which fresh frozen tissue was available. The immunohistochemical markers stained positive in the majority of canine PPGLs. Genetic screening of the canine tumors revealed the previously described variants in four cases; SDHB p.Arg38Gln (n = 1) and SDHD p.Lys122Arg (n = 3). Furthermore, the SNP arrays revealed large chromosomal alterations of which the loss of chromosome 5, partly homologous to human chromosome 1p and chromosome 11, was the most frequent finding (100% of the six cases with chromosomal alterations). In conclusion, canine and human PPGLs show similar genomic alterations, suggestive of common interspecies PPGL-related pathways.

Retrospective evaluation of toceranib phosphate (Palladia®) use in the treatment of inoperable, metastatic, or recurrent canine pheochromocytomas: 5 dogs (2014-2017)

BACKGROUND

Effective treatment options for inoperable, metastatic, or recurrent canine pheochromocytomas are lacking. In humans, specific germline mutations exist that drive the development of pheochromocytomas. Pharmaceutical blockade of these abnormalities with small molecule inhibitors are an effective treatment strategy. Similar mutations may exist in the dog, and thus, treatment with similar small molecule inhibitors may provide a survival advantage. The purpose of this study was to assess the role of toceranib phosphate in the treatment of inoperable, metastatic, or recurrent canine pheochromocytomas.

RESULTS

Retrospectively, medical records of dogs that had a diagnosis or suspect diagnosis of a pheochromocytoma were reviewed for information regarding response to toceranib phosphate and overall outcome. Five dogs were identified that fit the inclusion criteria. All five experienced clinical benefit (1 partial response, 4 stable disease). Progression-free interval (PFI) for the dog with the partial response was 61 weeks. PFI for the two dogs with stable measurable disease were 36 weeks and 28 weeks. PFI in the two dogs with stable metastatic disease were at least 11 weeks and 18 weeks.

CONCLUSIONS

Based on this limited series of dogs, the results suggest that toceranib may have biological activity in dogs with primary and metastatic pheochromocytomas. Larger studies are needed to define the use and response to toceranib in dogs with gross, microscopic, and metastatic pheochromocytoma.