Retrospective study of 20 cats surgically treated for insulinoma.

OBJECTIVE: To report the clinical signs, histopathology results, and prognostic factors for outcomes following excision for feline insulinoma (INS). STUDY DESIGN: Retrospective study. SAMPLE POPULATION: Twenty client-owned cats. METHODS: Medical records from 2006 to 2020 were reviewed by Veterinary Society of Surgical Oncology members for cats with hypoglycemia resulting from INS, with surgical excision and follow up. Clinical signs and histopathology results were summarized. Factors potentially related to disease-free interval (DFI), disease-related death (DRD), and overall survival time (OST) were analyzed with a Cox proportional hazards regression analysis. RESULTS: All cats were hypoglycemic on presentation with neurologic signs in 18 out of 20 and inappropriate insulin levels in 12/13. Excision of insulinomas resulted in immediate euglycemia or hyperglycemia in 18 cats. Eighteen cats survived to hospital discharge. The median time to death or last postoperative follow up was 664 days (range: 2-1205 days). Prognostic factors included age at presentation (for DFI); time to postoperative euglycemia (for DRD); preoperative and postoperative serum blood glucose concentrations; metastasis at the time of surgery (DFI and DRD), and histopathologic tumor invasion (for OST). The median OST for all cats was 863 days. The 1-, 2- and 3-year survival rates were 75%, 51%, and 10%, respectively. CONCLUSION: Excision of insulinoma resulted in euglycemia or hyperglycemia in most cats. Negative prognostic factors included young age, low serum glucose concentrations, metastasis at time of surgery, tumor invasion, and shorter time to euglycemia. CLINICAL SIGNIFICANCE: Surgical excision resulted in survival times comparable to those of canine INS.

Confirmed and presumed canine insulinomas and their presumed metastases are most conspicuous in the late arterial phase in a triple arterial phase CT protocol.

Arterial enhancement is the commonly described characteristic of canine insulinomas in contrast-enhanced computed tomography (CECT). However, this finding is also reported as inconsistent. The main aim of this single-center retrospective observational study was to describe the contrast enhancement (CE) pattern of canine presumed and confirmed insulinomas and presumed metastases in three consecutive (early, mid, and late) arterial phases. Included dogs had a medical-record-based clinical or cytological/histopathological diagnosis of insulinoma and quadruple-phase CECT. The arterial phases were identified according to published literature. The arterial enhancement of confirmed and presumed lesions was assessed using a visual grading score. Twelve dogs with a total of 17 pancreatic nodules were analyzed. Three dogs had multiple pancreatic nodules and nine had solitary findings. Four insulinomas were histopathologically confirmed. Late arterial phase (LAP) images demonstrated the largest number of pancreatic nodules reaching the highest enhancement scores (n = 13, 76%). All analyzed dogs had CT evidence of arterially enhancing nodules in the liver (n = 12), seven in the hepatic, splenic, or colic lymph nodes, and three in the spleen. Three out of five sampled livers and three lymph nodes were metastatic. All sampled spleens were benign. Avid arterial enhancement was the most dominant feature of canine presumed and confirmed insulinomas and presumed metastases in quadruple-phase CECT. The highest enhancement scores were observed primarily in LAP, followed by MAP. Authors, therefore, recommend including LAP in the standard CT protocol for dogs with suspected pancreatic insulinomas.

Gastrointestinal Intramural Pancreatic Pseudocysts in a Dog: A Case Report and Human Literature Review.

A 9.5 yr old Yorkshire terrier presented with chronic intermittent vomiting and lethargy of 1.5 yr duration that progressed to generalized weakness. Insulin:glucose ratio was consistent with an insulinoma. Triple-phase computed tomography revealed a mid-body pancreatic nodule. The mid-body pancreatic nodule was enucleated; histopathology was consistent with an insulinoma. Two weeks after the operation, the dog presented for anorexia and diarrhea. Abdominal ultrasound revealed a thick-walled cystic lesion along the dorsal stomach wall. An intramural gastric pseudocyst was diagnosed via exploratory laparotomy and intraoperative gastroscopy. Comparison of amylase and lipase levels of the cystic fluid with that of concurrent blood serum samples confirmed the lesion was of pancreatic pseudocyst origin. The gastric pseudocyst was omentalized. Two weeks after the operation, the dog re-presented for anorexia, regurgitation, and diarrhea. An intramural duodenal pseudocyst was identified and treated with a duodenal resection and anastomosis. The dog has remained asymptomatic and recurrence free based on serial abdominal ultrasounds 22 mo following insulinoma removal. To our knowledge, this phenomenon of pancreatic pseudocysts forming in organs other than the pancreas has not been reported in dogs. This case report and comprehensive human literature review purpose is to raise awareness of this disease process in dogs.

Evaluation of palliative therapy, alone or in combination with toceranib phosphate, in dogs diagnosed with metastatic or recurrent beta-cell neoplasia.

AIMS: To compare survival in dogs with recurrent or metastatic insulinomas that were treated with palliative therapy, alone or in combination with toceranib phosphate and to assess tolerability of the combined therapy in dogs. MATERIALS AND METHODS: Dogs diagnosed with insulinoma were retrospectively identified in the records of the Veterinary Teaching Hospital Complutense (Madrid, Spain). Diagnosis of insulinoma was based on clinical signs of hypoglycaemia, concentrations in serum of glucose <3.3 mmol/L and insulin >10 µIU/mL and presence of a pancreatic mass on diagnostic imaging. Dogs were treated surgically or medically, according to clinical stage established by imaging techniques, and monitored with blood and urine analyses monthly and abdominal ultrasonography every 3 months until death. Dogs that presented with metastatic disease at diagnosis or with recurrent hypoglycaemia after surgery were treated, according to the owner's decision, with one of two treatment protocols: palliative therapy alone (control group, n=7: diet, prednisone, famotidine or omeprazole, ±octreotide) or palliative therapy in combination with toceranib (treatment group, n=5; median dose of toceranib 2.52 mg/kg). Overall survival time (OST) and adverse events were compared between the two treatment groups. RESULTS: The OST was longer in the treatment group (median 399, min 125, max 476 days) compared to the control group (median 67, min 23, max 387 days; p=0.042). Dogs in the treatment group had a higher incidence of grade 1-2 gastrointestinal toxicity (diarrhoea) than dogs in the control group (p=0.010). In all cases, gastrointestinal toxicity was solved by temporarily discontinuing toceranib. CONCLUSIONS AND CLINICAL RELEVANCE: The use of toceranib combined with palliative treatment in dogs with suspect metastatic or recurrent insulinomas increased survival time and was adequate tolerated.

Glucagon therapy in canines with an insulinoma: A retrospective descriptive study of 11 dogs.

Canine insulinomas are uncommon neoplasms, which often result in refractory hypoglycemia. Glucagon is one readily available treatment for insulin-induced hypoglycemia. The primary objective of this study was to evaluate blood glucose trends and outcome (survival to discharge versus death or euthanasia) for dogs with insulinoma that were treated with glucagon. Secondary objectives included the description and influence of other variables such as abnormalities on diagnostic tests, physical examination abnormalities, concurrent administration of dextrose and/or glucocorticoids, and seizures. The median glucagon constant rate infusion dose was significantly higher for the non-survivors than for survivors. No other correlation was found between any of the independent variables evaluated when comparing blood glucose trends, length of hospitalization, and outcome. The main conclusion of the study is that glucagon therapy in insulinomas is an effective treatment to manage hypoglycemia.

Thérapie au glucagon de chiens avec un insulinome: étude rétrospective descriptive de 11 chiens. Les insulinomes canins sont des néoplasmes peu fréquents, qui résultent souvent en hypoglycémie réfractaire. Le glucagon est un traitement facilement disponible pour l'hypoglycémie induite par l'insuline. L'objectif primaire de la présente étude était d'évaluer les tendances du glucose sanguin et l'issu (survie jusqu'au congé versus décès ou euthanasie) de chiens avec insulinome qui furent traités avec du glucagon. Les objectifs secondaires incluaient la description et l'influence d'autres variables telles que des anomalies lors des tests diagnostiques et des examens physiques, l'administration concomitante de dextrose et/ou de glucocorticoïdes, et des convulsions. La dose médiane de perfusion à taux constant de glucagon était significativement plus élevée pour les non-survivants que pour les survivants. Aucune autre corrélation ne fut trouvée entre l'une ou l'autre des variables indépendantes évaluées lors de comparaisons avec les tendances du glucose sanguin, la durée de l'hospitalisation, et l'issu. La principale conclusion de cette étude est que la thérapie au glucagon lors d'insulinomes est un traitement efficace pour gérer l'hypoglycémie.(Traduit par Dr Serge Messier).

Canine insulinomas appear hyperintense on MRI T2-weighted images and isointense on T1-weighted images.

Clinical and imaging diagnosis of canine insulinomas has proven difficult due to nonspecific clinical signs and the small size of these tumors. The aim of this retrospective case series study was to describe MRI findings in a group of dogs with pancreatic insulinomas. Included dogs were presented for suspected pancreatic insulinoma, MRI was used to assist with localization of the primary lesion, and the diagnosis was confirmed with surgical exploratory laparotomy and histopathology. The MRI studies for each dog were retrieved and the following data were recorded: T1-weighted and T2-weighted signal intensities, type of contrast enhancement, size and location of the primary lesion, and characteristics of metastatic lesions (if present). A total of four dogs were sampled. In all patients, the insulinoma displayed high-intensity signal on T2-weighted fat saturation images, similar to human studies. On postcontrast T1-weighted fat saturation images, the tumors were primarily isointense to normal pancreatic tissue, in contrast to human studies where a low-intensity signal is typically identified. Abnormal islet tissue was detected with MRI in all four dogs and metastases were identified in three dogs. Variations in the MRI appearance of primary and metastatic lesions were identified and could have been related to the variation of tissue composition, including the presence of neoplastic cells, hemorrhage, and fibrovascular stroma, and to the transformation of this tissue throughout the disease process.

Risk factors for gastrointestinal upset and evaluation of outcome following surgical resection of canine pancreatic ß-cell tumors.

The objective of this study was to determine risk factors for vomiting and inappetence and evaluate long-term outcome after surgical treatment of pancreatic ß-cell tumors in dogs. Records of 33 dogs that underwent surgery for such tumors were retrospectively evaluated. Inappetence and vomiting occurred in 27.3% and 24.2% of dogs, respectively. Risk factors for postoperative vomiting were longer duration of clinical signs before surgery, higher preoperative total protein concentration, and lack of liver metastasis. No significant risk factors for inappetence or survival were identified. Median survival time was 723 days. Dogs with a longer duration of clinical signs before surgery may have had greater pancreatic involvement or more pronounced systemic perturbations. Higher preoperative total protein concentration may reflect preoperative dehydration or inflammation. Significance of lack of liver metastasis is unknown. The long survival time indicates a good overall prognosis with surgical treatment, justifying surgical intervention in patients with advanced disease.

Facteurs de risque pour les dérangements gastro-intestinaux et évaluation des résultats à la suite de la résection chirurgicale de tumeurs des cellules ß pancréatiques canines. L'objectif de la présente étude était de déterminer les facteurs de risque pour les vomissements et l'inappétence, et d'évaluer les résultats à long terme à la suite du traitement chirurgical de tumeurs des cellules ß pancréatiques chez des chiens. Les dossiers de 33 chiens qui subirent une chirurgie pour de telles tumeurs furent évalués rétrospectivement. L'inappétence et des vomissements se produisirent chez 27,3 % et 24,2 % des chiens, respectivement. Les facteurs de risque pour des vomissements post-opératoires étaient une durée plus longue des signes cliniques avant la chirurgie, une concentration pré-opératoire des protéines totales plus élevée, et l'absence de métastase hépatique. Aucun facteur de risque significatif pour l'inappétence ou la survie ne fut identifié. La médiane du temps de survie était de 723 jours. Les chiens avec une durée plus longue de signes cliniques avant la chirurgie pourraient avoir eu une plus grande atteinte pancréatique ou des perturbations systémiques plus prononcées. Des concentrations pré-opératoires de protéines totales plus élevées pourraient refléter une déshydratation pré-opératoire ou de l'inflammation. La signification de l'absence de métastase hépatique est inconnue. Le temps de survie prolongé indique un bon pronostic général avec le traitement chirurgical, justifiant ainsi l'intervention chirurgicale chez des patients dont la maladie est à un stade avancé.(Traduit par Dr Serge Messier).

Ultrasonographic features of insulinoma in six ferrets.

Insulinoma is a functional, insulin-secreting tumor, arising from the beta islet cells of the pancreas. It is one of the most common neoplasms in ferrets and has been associated with clinical signs of hypoglycemia, such as ptyalism, pawing at the mouth, seizures, lethargy, and coma. The ultrasonographic features of insulinoma in ferrets have not been previously reported. The purpose of this retrospective case series study was to describe the ultrasonographic features of confirmed insulinoma in a group of ferrets. Inclusion criteria were abdominal ultrasound examination and histological confirmed insulinoma by surgical biopsy. Six ferrets met the inclusion criteria, all of which had multiple hypoglycemic episodes. Ultrasonographic images were reviewed and the characteristics of the pancreatic nodules were recorded. Twenty-eight pancreatic nodules were observed in the six ferrets and were primarily hypoechoic (89.3%, 25/28) and homogenous (46.4%, 13/28) with a smooth margin (78.6%, 22/28). The distribution of the pancreatic nodules was 46.4% in the left lobe, 50% in the right lobe, and 3.6% in the body of the pancreas. The sizes of the pancreatic nodules varied from 1.5 × 1.5 to 4.1 × 5.6 mm. All of the pancreatic nodules removed from surgery were histopathologically confirmed as insulinoma. The findings indicated that insulinoma in ferrets could be detected through ultrasonography, which may facilitate diagnosis and preoperative surgical planning.

Contrast-enhanced ultrasonographic findings in three dogs with pancreatic insulinoma.

Abdominal ultrasonography is one of the most common diagnostic imaging modalities used for dogs with suspected insulinoma; however, pancreatic masses are clearly identified in fewer than half of affected dogs and benign pancreatic nodules can be difficult to differentiate from malignant ones. The purpose of this prospective study was to describe contrast-enhanced ultrasonography (CEUS) characteristics of confirmed pancreatic insulinoma in a group of dogs. Inclusion criteria were as follows: (1) repeated hypoglycemia (blood glucose levels <60 mg/dl, twice or more); (2) elevated blood insulin levels with hypoglycemia; (3) pancreatic nodules detected with conventional ultrasonography; and (4) histological confirmation of pancreatic islet cell carcinoma. Immediately following conventional ultrasonography of the entire abdomen, CEUS of the pancreatic nodule and adjacent parenchyma was performed using contrast-specific technology pulse inversion imaging and perflubutane microbubble contrast agent. Three dogs met inclusion criteria. Pancreatic nodules in all the three dogs became more clearly demarcated after injection of the contrast agent. Each nodule showed different enhancement patterns: markedly hyperechoic for 5 s, slightly hyperechoic for 1 s, and clearly hypoechoic for over 30 s. These results were not in complete agreement with previously reported CEUS findings in human patients with insulinoma. All nodules were surgically resected and histopathologically confirmed as malignant insulinomas. Findings from the current study indicated that contrast-enhanced ultrasound may help to increase conspicuity of pancreatic insulinomas in dogs and that enhancement characteristics may be more variable in dogs than in humans.

Prolonged survival in an aged Labrador retriever with a metastatic insulinoma.

This case report highlights an unusually prolonged, asymptomatic, disease-free interval in an aged male Labrador retriever that underwent partial pancreatectomy for a functionally active pancreatic insulinoma with histologically confirmed hepatic metastasis. The patient developed pancreatitis and nonseptic suppurative peritonitis 24 hr after surgical resection of the insulinoma and was managed medically until discharge. Three mo after surgery, the dog was diagnosed with exocrine pancreatic insufficiency (EPI) that was effectively managed with parenteral pancreatic enzymes. Due to normal glucose levels 3 mo postsurgically, liver samples from the initial surgery were resubmitted for immunohistochemistry. Results confirmed insulinoma metastasis with insulin expression. Ten mo postsurgically, the blood glucose was normal and serum insulin levels were slightly above the upper reference limit. The first hypoglycemic episode was documented 23 mo postoperatively, which was effectively managed with prednisone. The cause for the prolonged disease remission and survival was unknown, but was possibly a result of pancreatitis and peritonitis, partial spontaneous regression of metastatic lesions, or idiopathic. Despite life-threatening postoperative complications, this patient enjoyed a profoundly longer than expected survival. This case highlights the importance of removing the primary tumor (insulinoma) despite the presence of metastatic disease.

Ectopic insulinoma in a dog with insulin-induced hypoglycemia: a case report.

A 7-year-old spayed female Shih Tzu dog was presented for evaluation of recurrent hypoglycemia. Serum insulin levels during hypoglycemia were 35.3 µIU/mL. Ultrasonography and computed tomography showed a mesenteric nodule between the kidney and the portal vein, but no pancreatic mass was observed. During surgery, the nodule had neither anatomical adhesions nor vascular connections to the pancreas. Pancreatic inspection and palpation revealed no abnormalities. Hypoglycemia improved after resection of the nodule. Histopathological examination confirmed the nodule to be an islet cell carcinoma. Although extremely rare, ectopic insulinoma should be considered as a possible cause of insulin-induced hypoglycemia in dogs.

Serum insulin concentration in dogs with insulinoma as a clinical marker for presence of metastasis at the time of diagnosis.

BACKGROUND: Information regarding serum insulin concentration in dogs newly diagnosed with insulinoma and its association with clinical stage and survival time is lacking. OBJECTIVE: Examine association between serum insulin concentration and survival and clinical disease stage in dogs with insulinoma. ANIMALS: Fifty-nine client-owned dogs with a diagnosis of insulinoma from 2 referral hospitals. METHOD: Retrospective observational study. The χ2 test was used to compare the proportion of dogs with increased insulin concentration in groups with or without metastasis at the time of diagnosis. Linear mixed-effect models were built to compare differences in insulin concentration between dogs with and without evidence of metastasis at the time of original diagnosis. Cox's proportional hazards regression and Kaplan-Meier graphs were used to evaluate the association between insulin concentration and insulin groups and survival. RESULTS: Median serum insulin concentration was 33 mIU/L (range, 8-200 mIU/L) in dogs with World Health Organization (WHO) stage I disease and 45 mIU/L (range, 12-213 mIU/L) in dogs with WHO stage II and III disease. No difference was found in the proportion of dogs with increased insulin concentration with or without metastasis (P = .09). No association was identified between insulin concentration and survival (P = .63), and between dogs grouped by insulin concentration and survival (P = .51). CONCLUSIONS AND CLINICAL IMPORTANCE: Serum insulin concentrations were not different between dogs with or without metastasis at diagnosis. The degree of insulinemia does not provide further information regarding the stage of the disease and is not associated with survival time in dogs with insulinoma.

Multiple endocrine neoplasia in a sheep: insulinoma, adrenocortical carcinoma with myxoid differentiation, and thyroid C-cell carcinoma.

An ~10-y-old male sheep had anorexia and progressive weight loss for ~1 mo. The sheep was emaciated, and 20 d later, became recumbent and lethargic, and was hypoglycemic (0.33 mmol/L; RI: 2.6-4.4 mmol/L). The sheep was euthanized because of poor prognosis, and submitted for autopsy. We found no gross lesions in the pancreas; however, histologically, focal proliferations of round-to-polygonal cells were separated by connective tissue into small nests. These proliferating cells, which had abundant eosinophilic-to-amphophilic cytoplasm and hyperchromatic nuclei, were immunopositive for insulin and negative for glucagon and somatostatin; the lesion was diagnosed as an insulinoma. Insulinoma has not been reported previously in sheep, to our knowledge. In addition, autopsy and histologic examination revealed the presence of an adrenocortical carcinoma with myxoid differentiation and a thyroid C-cell carcinoma. Our case indicates that multiple endocrine neoplasms can occur in sheep, as in other animal species.

Insulinoma in dogs: a review.

Insulinomas are rare malignant functional pancreatic tumors of the ß cells that retain the ability to produce and secrete insulin. Insulinomas are the most common pancreatic neuroendocrine tumor in dogs that can induce a variety of clinical signs that result from hypoglycemia and secondary neuroglycopenic and adrenergic effects. Diagnosis and treatment is considered challenging, and the prognosis can be extremely variable depending on the therapeutic choices. This review aims to summarize and update classic knowledge with current trends in the diagnosis, treatment, and prognosis of insulinomas.

Blood glucose monitoring during surgery in dogs to assess completeness of surgical resection of insulinoma: 11 cases.

OBJECTIVE: To evaluate whether intraoperative detection of rising levels of blood glucose could improve the completeness of resection of insulin-secreting tumor tissue and whether this improves long-term outcomes. ANIMALS: 11 client-owned dogs diagnosed with insulinoma. PROCEDURES: Retrospective review of medical records of dogs undergoing partial pancreatectomy as treatment for insulinoma. A blood glucose reading was obtained at induction, following removal of the pancreatic mass and/or after each suspected metastatic lesion until blood glucose had normalized. Disease-free interval and survival time were measures of outcome. RESULTS: A positive increase in blood glucose was detected in all cases, with a mean rise of 6.35 ± 4.5 mmol/L. Mean follow-up was 611 days, mean disease-free interval was 382 days, and median survival time was 762 days. Tumor stage was not associated with outcome. Three cases underwent a second surgery (metastasectomy), achieving further prolongation of disease-free survival. CLINICAL RELEVANCE: A sustained increase in intraoperative blood glucose provided the surgeon with confidence of more complete resection of insulinoma tissue and resulted in improved outcomes in all cases included in this study. Subsequent metastasectomy of recurrent insulinoma lesions also provided good outcomes. Intraoperative monitoring of blood glucose during surgical treatment of insulinoma resulted in the surgeon continuing to explore and resect abnormal tissue until an increase of glycemia was observed. This was shown to provide the surgeon with more confidence of resection of all active insulinoma tissue and improved clinical outcomes.

Functional Insulinomas in a Rhesus Macaque (Macaca mulatta).

We report a rare case of functional insulinomas in a 16.7-year-old female Rhesus macaque (Macaca mulatta) that was presented with neuroglycopenic signs to the breeding colony hospital at the Tulane National Primate Research Center. At initial and follow-up examinations, the animal was consistently hypoglycaemic and was clinically maintained with additional fruits, other high-sugar food items and dextrose supplementation. Occasional episodes of seizure and collapse resolved quickly on administration of high-sugar food items. At necropsy, the uncinate process of the pancreas had a 2.2 cm diameter, red, round, firm neoplastic mass, and another neoplasm was identified on histological examination of the head of pancreas. Histologically, neoplastic cells exhibited neuroendocrine packeting, resembled pancreatic islet cells and immunolabelled for chromogranin A, synaptophysin and insulin but not for somatostatin, gastrin or pancreatic polypeptide. A few cells immunolabelled for glucagon. The clinical signs and gross and histological findings were consistent with functional insulinomas.

Contrast-enhanced ultrasound features of focal pancreatic lesions in dogs.

BACKGROUND: Contrast-enhanced ultrasound (CEUS) features of pancreatic lesions are poorly reported in veterinary literature. METHODS: Qualitative and quantitative features of pancreatic benign (nodular hyperplasia [NH], cyst and abscess) and malignant (adenocarcinoma and insulinoma) lesions during B-mode and CEUS examinations are described in 75 dogs. RESULTS: Adenocarcinomas (n = 23) had mixed echogenicity at B-mode, and they were hypoenhancing or non-enhancing at CEUS, with a non-homogeneous and cystic enhancement pattern. Insulinomas (n = 23) appeared as hypoechoic lesions at B-mode, and as hyperenhancing, homogeneous and solid lesions at CEUS. NH (n = 17) had an constant appearance, being hypoechoic at ultrasound (US) and isoenhancing at CEUS. Cysts (n = 7) were all anechoic, with acoustic enhancement clearly detectable at US, but were non-enhancing at CEUS. Lastly, abscesses (n = 5) had mixed echogenicity, and they showed both hyperenhancement and non-enhancement at CEUS. Hypoenhancement and non-homogeneous appearance had a moderate diagnostic accuracy in the detection of adenocarcinomas. In particular, hyperenhancement was evident only in malignant lesions (adenocarcinomas and insulinomas). CONCLUSION: CEUS, in combination with B-mode US features, is a valuable tool for distinction of benign and malignant abnormalities of the pancreas and can potentially differentiate insulinomas from adenocarcinomas.

Intrapancreatic accessory spleen mimicking pancreatic insulinoma with intrapancreatic metastasis in a cat.

An 11-year-old neutered male Domestic Shorthair cat presented with a 3-month history of hypoglycemia, two episodes of seizure, and intermittent tick-like signs. Serum biochemistry revealed severe hypoglycemia associated with high insulin concentrations. Dynamic abdominal computed tomography (CT) indicated two pancreatic masses, which were enhanced most during the late arterial phase but had different degrees and variations of attenuation. Partial pancreatectomy was performed. Histopathology and immunohistochemistry confirmed that one mass was an insulinoma and the other was an ectopic splenic tissue, consistent with the differences in imaging findings. When an intrapancreatic lesion with hyper-attenuation on dynamic abdominal CT is detected, not only insulinoma or metastasis of malignancies but also intrapancreatic accessory spleen (IPAS) should be considered as differential diagnoses.

Fluorine-18 fluorodeoxyglucose positron emission tomography-computed tomography for staging of canine insulinoma: 3 cases (2019-2020).

OBJECTIVES: Canine insulinomas are uncommon malignant functional pancreatic neuroendocrine tumours with a high metastatic rate. Diagnostic imaging aids with staging and surgical planning of these tumours; however, identification is unpredictable across modalities. High-grade human pancreatic neuroendocrine tumours display increased avidity on 18 F-fluorodeoxyglucose positron emission tomography-CT. MATERIALS AND METHODS: Dogs with clinicopathologic findings consistent with pancreatic insulinoma were prospectively enrolled. Patients underwent 18 F-fluorodeoxyglucose positron emission tomography-CT and CT angiography, followed by exploratory laparotomy. RESULTS: Three patients met the inclusion criteria and had histologically confirmed insulinomas. Both metastatic lesions in patient 1 were mildly avid (SUVmax 2.79 and 3.01). In patient 2, the primary pancreatic insulinoma was minimally avid (SUVmax 2.16). The primary pancreatic lesion in patient 3 had similar avidity to normal pancreatic parenchyma (SUVmax 1.54) and was undetected on 18 F-fluorodeoxyglucose positron emission tomography-CT. Insulinomas demonstrated variable attenuation and contrast enhancement patterns on CT angiography and certain lesions were more conspicuous than on 18 F-fluorodeoxyglucose positron emission tomography-CT. Two metastatic lesions not visible on either imaging modality were discovered in patient 2 at surgery. CLINICAL SIGNIFICANCE: Canine insulinomas were inconsistently avid on 18 F-fluorodeoxyglucose positron emission tomography-CT. This finding is likely attributable to the confounding clinicopathological features and multifaceted transformation of these tumours, in addition to the influence of variable tumour size, composition and vascularity. Unpredictable tumoural avidity limits the value of 18 F-fluorodeoxyglucose positron emission tomography-CT for staging canine insulinomas.