Retrospective evaluation of toceranib phosphate (Palladia) in the treatment of canine carcinomatosis and mesothelioma

Canine carcinomatosis (CC) and mesothelioma (CM) are rare but aggressive neoplasms that historically have been associated with poor prognoses. There is limited information regarding treatment for CC and CM. The purpose of this retrospective study was to evaluate the efficacy and tolerability of toceranib phosphate (Palladia) in dogs with CC and CM. Cases were solicited from the American College of Veterinary Internal Medicine (ACVIM) Oncology listserv and retrospectively reviewed. For eligibility, a cytologic and/or histopathologic diagnosis of CC or CM was required. A total of 23 cases were included (CC = 14, CM = 8, both = 1). Eighty-two percent (19/23) of dogs presented with effusion. The best overall response rate (BORR) was 30.4% (13% complete response [CR], 17.3% partial response [PR]). Stable disease (SD) was appreciated in 14 dogs (60.8%) including the four dogs without effusion. The most common toceranib-related adverse events were either Grade 1 and 2 diarrhea or hyporexia. The median progression-free survival (PFS) was 171 days (range, 7-519 days) and overall median survival time (MST) was 301 days (range, 49-875 days) for all dogs. When evaluating dogs solely with effusion, the median PFS and overall MST were 171 days (range, 7-519 days) and 285 days (range, 49-875 days), respectively. This report demonstrates that toceranib is both well tolerated and a potential treatment for CC and CM. A randomised, controlled, prospective study would be needed to objectively assess the survival benefit of toceranib in the management of CC and CM, with and without effusion.

Localized pleural mesothelioma in a dog

Malignant mesotheliomas with localized growth are extremely rare in dogs. A 9-year-old male dog presented with a localized tumour that originated from the parietal pleura and had polypoid growth in the thoracic cavity. Histological examination revealed that the tumour consisted of tubular formations with scattered cysts and minimal papillary growth pattern. Neoplastic cells were immunopositive for mesothelial markers (calretinin and Wilms' tumour gene 1) and negative for carcinoma markers (thyroid transcription factor 1 and tumour protein 63). The animal was alive with no recurrence or metastasis/dissemination 11 months after surgery. To the best of our knowledge, this is the first report of a localized mesothelioma in a dog without metastasis/dissemination and highlights the value of mesothelial markers for an accurate diagnosis.

Pleural mesothelioma in a California sea lion (Zalophus californianus)

A 25-year-old female California sea lion (Zalophus californianus) reared in an aquarium died following a history of anorexia, lethargy, abnormal protrusion of the skin, and oral respiration. At necropsy, multiple yellowish-white nodules with diameters of 0.1-0.5 cm were disseminated in the thoracic cavity and lungs. Histopathologically, the nodules were continuous with normal mesothelium and were characterized by the proliferation of spindle-shaped to polygonal neoplastic cells with prominent atypia. The neoplastic cells exhibited diffuse, strong staining for vimentin and partial, weak to moderate staining for cytokeratin AE1/AE3. Based on these findings, the lesions were diagnosed as pleural mesothelioma. This study reports the first case of pleural mesothelioma in California sea lion.

Biphasic pleural mesothelioma in a goat

An 8-year-old Saanen goat doe was seen for inappetence, tachycardia, and intermittent bluish-grey discoloration of the oral mucous membranes. On physical examination, the goat was mildly tachypneic and tachycardic, with reduced sounds auscultated on the left side of the thorax. Euthanasia was elected. Necropsy revealed an infiltrative, multinodular mass within the left thoracic cavity and innumerable small, tan nodules disseminated across the pleura of the lungs, thoracic walls, and diaphragm. Upon histologic examination, the mass was composed of highly pleomorphic, fusiform to polygonal cells. Neoplastic cells exhibited positive immunoreactivity for both cytokeratin and vimentin, consistent with a diagnosis of biphasic pleural mesothelioma. Key clinical message: Mesothelioma has rarely been described in the goat but should be considered as a differential diagnosis for thoracic masses in small ruminants, along with thymoma; metastatic neoplasia; carcinomatosis; and granulomatous lesions caused by parasites, bacteria, and fungi.

Malignant peritoneal mesothelioma in a boar who lived in Calabria (Italy): Wild animal as sentinel system of human health

Mesothelioma is a tumor of the serosal membranes described both in human and veterinary medicine. While in humans the relationship between mesothelioma and exposure to asbestos and some other asbestiform minerals is well known, in animals it is still difficult to establish. In this paper a case of malignant peritoneal mesothelioma probably related to asbestos exposure in a wild boar is described. At post-mortem evaluation the peritoneum, diaphragm and serosal surface of liver and kidneys showed isolated to coalescent multiple nodular lesions. Samples from diaphragm, liver and lung were collected to perform microbiological and histological investigations. To assess the presence of asbestos and/or other asbestiform minerals, SEM-EDS investigations were performed on organs and soil samples collected from the area where the wild boar lived. Microbiological investigations were negative for Mycobacterium species. Gross and histological examination were compatible with a biphasic mesothelioma, with nodules composed of epithelioid and sarcomatoid elements with high pleomorphism. Immunohistochemistry revealed only multifocal scattered positivity for WT-1 and D2-40. Asbestos fibres were detected in all samples (organs and soil) by SEM-EDS, demonstrating a potential relationship between the neoplasia and the exposure to naturally occurring asbestos (NOA). In conclusion, the results of the present study are further confirmation that wild animals, such as the boar, are suitable sentinels to indicate the risk of environmental exposure to asbestos for human populations.

Presumptive seeding metastasis of pericardial mesothelioma following repeated pericardiocentesis in a dog

A dog with a history of recurrent pericardial effusion that required repeated pericardiocentesis was presented to the surgical service at the Ontario Veterinary College Health Sciences Centre for thoracoscopic pericardiectomy. Physical examination revealed a subcutaneous mass in the right lateral thorax. Cytology of the subcutaneous mass and histopathology of the pericardium were consistent with mesothelioma. This article details the first reported case of pericardial mesothelioma with suspected extra-thoracic metastasis following pericardiocentesis in a dog.

Mesothelioma in the Calf

Three cases of mesothelioma in calves are described. Two were full-term foetuses, the other was 3 months old. There was ascites in all three. The tumours formed multiple, discrete nodules on the parietal and visceral peritoneum, and in the older calf also on the pleura. Lymph nodes were unaffected. The tumours appear to arise from the superficial layers of the serosa, and are considered to be of multicentric origin.

Canine Cardiac Mesothelioma with Granular Cell Morphology

Cardiac mesothelioma with granular cell features was diagnosed in a 10-year-old Golden Retriever presenting with pericardial and abdominal effusions. The diagnosis was based on gross, morphologic, and immunohistochemical features. The immunohistochemical profile of the neoplasm was pancytokeratin positive, vimentin positive, and S-100 negative; most gross and morphologic features were consistent with both mesothelioma and granular cell tumor. To the authors' knowledge, the prognosis for either primary cardiac mesothelioma or granular cell tumor in the dog is unknown. At 4 months after thoracotomy, pericardectomy, and mass excision, this dog was alive and without clinical evidence of pericardial or abdominal effusions. We describe a granular morphologic variant of cardiac mesothelioma in a dog.

Deciduoid Peritoneal Mesothelioma in a Dog

Deciduoid mesothelioma is a rare variant of epithelial mesothelioma, up to now only described in human pathology, which bears remarkable cytomorphologic resemblance to the endometrium of pregnancy, termed decidua. A case of peritoneal mesothelioma with deciduoid features in a 10-year-old, female dog is reported. Multiple whitish-gray nodules (1-5 mm in diameter) in parietal peritoneum and mesentery were histologically composed of large, proliferating, polygonal or ovoid cells with an abundant eosinophilic, glassy cytoplasm. Immunohistochemical evaluation indicated that the neoplastic cells coexpressed cytokeratin and vimentin with strong and diffuse cytoplasmic staining, and ultrastructural analysis showed long and slender mesothelial-type microvilli; these findings confirmed the mesothelial origin of the tumor.

Use of Immunohistochemical Marker Calretinin in the Diagnosis of a Diffuse Malignant Metastatic Mesothelioma in an Equine

Mesotheliomas are rarely reported in animal species. In this report, the occurrence of a diffuse, metastatic mesothelioma in a 6-year-old gray Arabian mare is described. The mare was presented on clinical examination with ascites, bilateral pleural effusion, and pleural roughening. Necropsy revealed abundant fluid in the abdominal and thoracic cavities. The surface of all organs was thick and fibrosed with multiple raised nodules and hemorrhages. Histology was characteristic of a generalized, biphasic mesothelioma with vascular and lymph nodes metastases. It is believed that the primary tumor developed in the pericardium and spread through lymphatics. In this report, calretinin was used as an immunohistochemical marker in the diagnosis of mesothelioma in an equine species for the first time.

Pericardial Mesothelioma in a Yellow-naped Amazon Parrot (Amazona auropalliata)

A 37-year-old female yellow-naped Amazon parrot (Amazona auropalliata) was presented with a history of lethargy, inappetence, and decreased vocalizations. On examination, the coelom was moderately distended and palpated fluctuant, and the heart was muffled on auscultation. Coelomic ultrasound, coelomocentesis, and radiographs were performed and revealed an enlarged cardiac silhouette and marked coelomic effusion. Pericardial effusion was confirmed by echocardiography. A well-circumscribed, hyperechoic soft tissue density was observed at the level of the right atrium on initial echocardiography; however, a cardiac mass was not identified by computed tomography scan or repeat echocardiograms. Ultrasound-guided pericardiocentesis was performed under anesthesia, and cytology results were consistent with hemorrhage; no neoplastic cells were identified. A repeat echocardiogram 4 days after pericardiocentesis revealed recurrence of the pericardial effusion. Due to the grave prognosis, the owners declined endoscopic pericardiectomy, and the patient died the following day. On postmortem examination, the pericardial surface of the heart was covered in a white to yellow, multinodular mass layer. Histologic analysis revealed a multinodular mass extending from the atria, running along the epicardium distally, and often extending into the myocardium. Neoplastic cells present in the heart mass and pericardium did not stain with a Churukian-Schenk stain, and thyroglobulin immunohistochemistry was negative. Cytokeratin and vimentin stains showed positive expression in the neoplastic cells within the mass. These results are consistent with a diagnosis of mesothelioma. This is the first report of mesothelioma in a psittacine bird.

Pulmonary alveolar microlithiasis with concurrent pleural mesothelioma in a dog

Pulmonary alveolar microlithiasis (PAM) is a rare pulmonary disorder characterized by the accumulation of calcium phosphate microliths within the alveoli, with only a few cases described in animals. A 10-year-old female Bulldog was euthanized due to history of dyspnea and recurrent pleural and pericardial effusions. At necropsy, numerous multifocal to coalescent protruding nodules of 1-5 mm in diameter were scattered throughout the thoracic serosal surfaces. Moreover, lungs showed a diffuse pale gray color and had a generalized fine grainy consistency. Histological investigations revealed abundant intra-alveolar laminated microliths that stained positive with periodic acid-Schiff and von Kossa stains. The pulmonary interstitium showed multifocal, mild to moderate thickening, due to collagen deposition and mild hyperplasia of type 2 pneumocytes. The pulmonary lesion was not associated with any inflammatory response, and mineral deposition was not observed in any other organ or tissue. In addition, pulmonary, pericardial, and pleural surfaces were extensively infiltrated by an epithelioid mesothelioma. Immunohistochemical staining revealed neoplastic cells that strongly coexpressed vimentin and cytokeratin, supporting the diagnosis of mesothelioma. An overview of PAM, including pathogenesis and histological characteristics, are discussed in relation to the concurrent pleural mesothelioma. The potential cause and effect relationship between the 2 conditions could neither be established nor ruled out.

A case of biphasic mesothelioma with osseous and chondromatous differentiation in a cat

An 11-year-old domestic short hair cat with dyspnea, cyanosis, and pleural effusion died. Necropsy revealed several nodules and masses on the parietal pleura, pericardium, and diaphragm. The tumor contained epithelial and mesenchymal components and displayed osseous and chondromatous differentiation. Tumors cells were positive for pancytokeratin and vimentin. This is the first report of a biphasic mesothelioma with osseous and chondromatous differentiation in this species.

A biphasic malignant mesothelioma of the peritoneum and pleura in a horse

This report describes the macroscopic, histologic, immunohistologic and ultrastructural characteristics ofa biphasic malignant mesothelioma in the peritoneal and pleural cavity of a 13-year-old Icelandic pony mare, which exhibited recurrent ascites clinically. Immunohistology was performed employing multiple monoclonal antibodies against cytokeratins (CK) and vimentin. The ultrastructural examination included the quantitative evaluation of the length to diameter ratio of the microvilli. Post mortem examination revealed a severe ascites and hydrothorax. The serosal surfaces of the peritoneum and pleura displayed poorly-demarcated, multifocal to coalescing laminar masses and small nodules. Histology revealed a bimorphic mass consisting of spindle-shaped cells and microcystic epithelioid areas. A transcoelomic and local invasive growth pattern as well as lymph node metastases were noticed. Immunohistology revealed a strong expression of CK. Though a low and moderate expression of CK5/6 and CK20 was present, respectively, CK7 and CK10-antigens were lacking. Ultrastructurally, the epithelioid mesothelioma cells displayed long microvilli, cytoplasmic tonofilaments, and desmosomes. Quantitative evaluation of the length to diameter ratio of the 10 longest microvilli revealed a mean value of approximately 16.2. Summarized, this report described the case of a malignant biphasic mesothelioma with an atypical CK20 expression but a characteristic ultrastructural morphology including long microvilli.

Spontaneous peritoneal malignant mesothelioma in a geriatric japanese macaque (Macaca fuscata)

A 28.5-year-old female Japanese macaque (Macaca fuscata) was euthanatized because of abdominal distension due to severe ascites. Nodular lesions of varying sizes up to 5 mm in diameter were distributed diffusely on the surface of the omentum, mesentery and parietal peritoneum. No neoplastic masses were detected in any visceral organ. The nodules were composed of proliferation of mono- or multi-layered epithelial-like cells occasionally showing papillary growth and sheets of small round or polygonal cells. Signet ring-like cells and tubular structures were occasionally present. Neoplastic cells were strongly positive to cytokeratin, and occasionally to vimentin. Based on gross and histopathological findings, this tumor was diagnosed as an epithelial type of peritoneal malignant mesothelioma, the first reported case in the non-human primates.

Palliative intravenous cisplatin treatment for concurrent peritoneal and pleural mesothelioma in a dog

A 10-year-old Maltese dog was presented with abdominal distention and dyspnea. Cytological examination of pleural and peritoneal effusion was suggestive of malignant effusion of glandular origin. Numerous, multifocal, tan to white nodules were disseminated throughout the surface of the abdominal organs and peritoneum at biopsy. Histologically, the tumors were revealed to be an epithelial type of mesothelioma. Neoplastic cells co-expressed cytokeratin and vimentin. Intravenous administration of cisplatin was chosen as the treatment. During treatment, the dog's overall body condition improved and the clinical signs were relieved without significant side effects. The survival time from diagnosis to sudden death by unknown cause was 153 days.

IMAGING DIAGNOSIS-CANINE THORACIC MESOTHELIOMA

A 12-year-old neutered female Pembroke Welsh Corgi had a 2-month history of a progressive, productive cough nonresponsive to therapy. Mild pleural effusion, right middle lung lobe collapse, and multiple subpleural nodular lesions were detected in thoracic radiographs and computed tomography (CT) images. Histopathologic diagnosis of the pleural nodules was mesothelioma. Mesothelioma should be considered in patients where pleural masses are detected in radiographs or CT images.

Portal site metastasis of invasive mesothelioma after diagnostic thoracoscopy in a dog

CASE DESCRIPTION

A 10-year-old Golden Retriever evaluated because of recurrent pericardial and pleural effusion underwent thoracoscopy with biopsy of the pleura and mediastinum.

CLINICAL FINDINGS

Before thoracoscopy, 5 L of serosanguinous fluid was removed from the pleural cavity via thoracocentesis. During thoracoscopic exploration, it was observed that the parietal pleura and mediastinum were covered by miliary white to tan nodules 1 to 3 mm in diameter. Biopsy specimens were obtained, and partial pericardiectomy was performed. Portal sites were closed routinely. Cytologic evaluation of the pleural fluid revealed high protein concentration and cellularity, with cellular changes consistent with an exfoliating carcinoma. Results of bacterial culture were negative.

TREATMENT AND OUTCOME

Carboplatin was administered via intracavitary instillation, and prednisone was administered orally. Twenty-one days later, 1 firm, irregularly shaped 6.5 x 3-cm mass and 4 smaller masses were detected in the area of the left thoracic wall where the cannula had been inserted during thoracoscopy. Histologic analysis of tissue from the masses collected at necropsy confirmed that they were malignant tumors with similar appearance to the pleural mesothelioma and immunohistochemical staining properties identical to those of the primary tumor.

CLINICAL RELEVANCE

Although thoracoscopy is associated with less postoperative pain, shorter hospitalization times, and faster patient recovery than sternotomy procedures, complications are also possible with minimally invasive endoscopic surgery. Portal site metastasis can develop from contamination of portal sites with cells on instruments or cannulas or via leakage of effusion fluid. Although rare, this potential complication should be discussed with owners prior to performing the procedure.

Hemidiaphragmatic reconstruction with a transversus abdominis muscle flap after resection of a solitary diaphragmatic mesothelioma in a dog

CASE DESCRIPTION

A 2-year-old Siberian Husky was evaluated because of a 2-week history of coughing and gagging and decreased appetite and activity level.

CLINICAL FINDINGS

Radiography, surgery, and immunohistochemical examination revealed a solitary sclerosing mesothelioma extending from the left thoracic diaphragmatic surface that was adherent to the pericardium and the caudal mediastinum.

TREATMENT AND OUTCOME

The tumor was resected along with most of the left hemidiaphragm, and the left transversus abdominis muscle was used to reconstruct the diaphragm. The 13th rib formed the base of the muscle flap. The muscle flap was transposed into the defect so that the mesothelium-lined surface faced the thoracic cavity and the deep aspect of the muscle formed the abdominal surface of the diaphragm. To minimize risk of adhesions, the exposed raw aspect of the abdominal surface was covered with porcine small intestinal submucosa. Recovery was uncomplicated, and the dog's appetite and activity level soon returned to normal. Evaluation 54 days after surgery revealed 2 subcutaneous masses on the thorax and masses in the liver and both kidneys; histologic and immunohistochemical analyses revealed metastasis of the original tumor. The dog was euthanatized.

CLINICAL RELEVANCE

Hemidiaphragmatic reconstruction with a transversus abdominis muscle flap after resection of a diaphragmatic tumor was successful. The muscle flap was easily harvested and transposed into the diaphragmatic defect.

Ten cases of feline mesothelioma: an immunohistochemical and ultrastructural study

In the cat only 10 cases of mesothelioma, mainly of the peritoneum, have been previously reported. This paper describes a further 10 cases, eight pleural and two peritoneal, in males and females aged 1-17 years. Histologically, five tumours were epithelial, three fibrosarcomatous and two biphasic. Immunohistochemical markers used in human pathology for the identification of mesotheliomas include vimentin, cytokeratin (CK) AE1/AE3, HBME-1, CK 5/6, calretinin, thrombomodulin, carcinoembryonic antigen (CEA), CD15, E-cadherin and desmin. All 10 feline mesotheliomas were positive for vimentin and CK AE1/AE3, six were positive for HBME-1, two for CK5/6, three for CEA and four for E-cadherin. All were negative for desmin and calretinin. Antibodies to thrombomodulin and CD15 failed to cross-react with feline tissues. Electron microscopy, performed in four cases, revealed microvillar structures, desmosomes and intracytoplasmic lumina, confirming its value as a diagnostic tool. The study showed that mesothelial marker antibodies commonly used in human patients can be used for the diagnosis of feline mesothelioma, preferably as a panel of antibodies rather than only one.

Pericardial Mesothelioma in a Neonatal Calf

We encountered an extremely rare tumor, a pericardial mesothelioma, in a neonatal calf. The patient calf showed severe abdominal distention, and died immediately after birth. The thoracic cavity was contained a huge heart with a large amount of pericardial fluid. A number of granular and cobblestone-like nodules were dispersed over the epicardium and pericardium. The nodules consisted of papillary proliferations of neoplastic cells, and the neoplasm occasionally showed mesenchymal proliferations. Immunohistochemistry revealed that they had the characteristics of mesothelial cells (cytokeratin-and vimentin-positive), and the neoplasm was diagnosed as mesothelioma.

Palliative intracavitary carboplatin therapy in a cat with suspected pleural mesothelioma

A 12-year-old neutered male oriental shorthair cat was referred to the Animal Health Trust for investigation of pleural effusion. Ultrasonography revealed marked irregular thickening of the pleural surface of the cranial and caudal mediastinum. Cytological examination of the pleural fluid and fine needle aspirates of the thickened pleura suggested a diagnosis of mesothelioma. Following complete drainage of the thoracic cavity under ultrasound guidance, 180 mg/m2 carboplatin diluted in 60 ml sterile water was infused into the pleural space (30 ml in each hemithorax). This resulted in complete resolution of clinical signs for 34 days (having required thoracocentesis on four occasions in the preceding 4 weeks). The procedure was repeated using 200 mg/m2 carboplatin, and there was a further 20-day period where the cat was free of clinical signs. Further treatment was declined and the cat was euthanased 120 days after initial presentation. This is the first report of successful palliative chemotherapy for suspected feline mesothelioma and suggests that intracavitary carboplatin could be considered in tumours affecting the pleural cavity.

Invasive epithelial mesothelioma in a dog

This report describes the gross, microscopic, and immunohistochemical features of an invasive epithelial mesothelioma in an 11-year-old neutered male Golden Retriever. The tumor involved the pericardium, pleura, mediastinum, and peritoneum and invaded into submesothelial tissues. Neoplastic cells in the thoracic fluid showed prominent features of malignancy in a background of mixed inflammatory cells and scattered erythrocytes. Histologically, the tumor consisted of nests of epithelioid cells with frequent mitotic figures and multinucleation that infiltrated submesothelial tissues. Neoplastic cells strongly coexpressed vimentin and cytokeratin intermediate filaments, which assisted in the differentiation from other epithelial tumors of nonmesothelial origin.

Malignant pleural mesothelioma in a woodchuck (Marmota monax)

A spontaneous pleural mesothelioma was observed in a 4-year-old female woodchuck (Marmota monax). At necropsy, multifocal, tan to white, firm discrete nodules, 2 to 40 mm in diameter, were scattered over the ventral parts of the lungs and their corresponding parts of the diaphragm and the thoracic wall. Histopathologically, the tumor cells were large, cuboidal-shaped and variable size, and were weakly positive with PAS and Alcian blue. Immunohistochemically, neoplastic cells were positive for both vimentin and cytokeratin, indicating mesothelial origin. This report represents, as far as we know, the first reported case of a spontaneous mesothelioma in woodchucks.

Development of pericardial mesothelioma in golden retrievers with a long-term history of idiopathic haemorrhagic pericardial effusion

This report describes the development of pericardial mesothelioma in five golden retrievers with a long-term history of idiopathic haemorrhagic pericardial effusion (IHPE). These five dogs were treated with repeated pericardiocentesis for recurrent episodes of pericardial fluid accumulation; other than IHPE, all potential causes of this fluid accumulation were ruled out by the results of diagnostic imaging and cytology and bacterial or fungal culture of fluid obtained during pericardiocentesis. In three dogs that eventually underwent pericardiectomy, neoplastic lesions were not detected in any organs or tissues within the thoracic cavity during the surgical procedure, and the surgical biopsies were consistent with IHPE. In one of the three dogs, however, cytology of recurrent thoracic effusion revealed clusters of neoplastic mesothelial cells from 1 month after surgical intervention until death. The clinical course of the disease ranged from 30 to 54 months between the first visit and death, and on post-mortem examination pericardial mesothelioma was diagnosed in all five dogs. The clinical observations, together with the breed and age of the affected animals, suggested that the five dogs initially suffered from IHPE, which was then followed by the development of pericardial mesothelioma. It is possible that IHPE is associated with the development of pericardial mesothelioma in golden retrievers through a chronic inflammatory process.

Peritoneal Biphasic Mesothelioma in a Dog

A 10-year-old German shepherd dog was presented with a severe abdominal distension. At necropsy, whitish and firm mass was observed in the mesentery with metastases in the pericardium and pleura. The intestinal serosa was thickened and stiff. Histologically, the tumours were composed of a biphasic population of cells, which reacted with cytokeratin, vimentin and Wilms' tumour 1 protein antibody. Ultrastructural examination revealed numerous microvilli, abundant rough endoplasmic reticulum, numerous desmosomes and bundles of microfilament. The tumour was classified as biphasic mesothelioma of peritoneal origin.

Sclerosing Peritoneal Mesothelioma in a Dog - A Case Report

A case of peritoneal sclerosing mesothelioma in a 3-year-old German shepherd dog is reported. The dog presented a severe abdominal distension. Cytological examination of the peritoneal fluid revealed anaplastic epithelioid cells. Necropsy findings revealed an irregular-shaped mass attached to the pancreas and stomach with numerous nodules covering the intestinal and urinary bladder serosa. The diagnosis was made by histology and immunohistochemistry, with cytokeratin, vimentin and calretinin antibodies. Differential diagnosis with chronic peritonitis and spreading of abdominal primary carcinoma is discussed.

Use of pericardial fluid pH to distinguish between idiopathic and neoplastic effusions

Pericardial effusion (PE) resulting from neoplasia usually is associated with a poor prognosis, whereas idiopathic PE frequently has a good prognosis. This study examined the utility of pH measurement to distinguish between these 2 etiologies. Dogs were classified as having idiopathic PE (n = 12) if pericarditis was diagnosed on histopathology (n = 4) or if no historical, physical, or echocardiographic evidence of recurrent PE was present for at least 6 months after pericardiocentesis (n = 8). Dogs were classified as having neoplastic PE (n = 25) if pericardial or myocardial neoplasia was detected on histopathology (n = 11) or a discrete mass associated with the right atrium, right ventricle, or the aorta was visualized on echocardiography (n = 14). Samples of PE were centrifuged and the supernatant pH was measured with a portable pH meter. The lowest pH (6.40) was found in a dog with idiopathic PE and the highest pH (7.85) was found in a dog with neoplastic PE. However, data from the 2 groups overlapped in 33 out of 37 (89%) instances, and median pH from the idiopathic and neoplastic groups was not significantly different (7.40 and 7.47, respectively; P = 0.28; difference in medians = -0.7; 95% CI, -0.26-0.06). Because of the degree of overlap, our data provide little justification for the use of pH measurement as a diagnostic test in cases of PE.

Pleural mesothelioma in a young cat

A mesothelioma was seen as an incidental finding in the thoracic cavity of an eleven-month old female cat. At necropsy, the pale nodular lesions were spread over the ventral parts of the lungs and their corresponding parts of the diaphragm and the thoracic wall. Microscopically, the tumor consisted of mesenchymal tissue with large amounts of collagenous fibers covered by a mainly unilayered, polymorphic, partly vacuolated line of cells with large nuclei. Mitotic figures were rare. Based on morphological appearance the lesion was classified as an early mesothelioma.

[Cardiac tamponade due to pericardial mesothelioma in an 11-year-old dog: diagnosis, medical and interventional treatments]

In a dog presenting with the clinical signs of exercise intolerance and ascites, cardiac tamponade due to suspected idiopathic pericarditis was diagnosed based on thoracic radiographs, electrocardiogram (EKG) and cardiac ultrasound. Pericardial effusion recurred soon after pericardiocenteses, prescription of colchizine and again after balloon pericardiotomy. After partial pericardectomy by thoracoscopy and after obtaining a histological diagnosis of mesothelioma adjuvant intracavitary chemotherapy using cisplatin was performed. Already one week later the dog developed marked dyspnea due to severe pleural effusion. The dog was maintained at acceptable life quality judged based on playfulness and appetite using repeated pleuro-centeses for an additional two months, when the dog was euthanized due to uncontrollable pleural effusion. Despite extensive treatments life span from initial presentation to euthanasia was only 5 months. Necropsy revealed extensive mesothelioma metastases covering the whole pleura, epicardium and remaining pericardium. Diagnostic and therapeutic aspects of (recurrent) pericardial effusion are discussed based on this case.

Hepatic cholangiocarcinoma and testicular mesothelioma in a wild-caught blue shark, Prionace glauca (L.)

An adult male blue shark, Prionace glauca (L.), caught in July 2000 by a recreational fisherman off Long Island, New York, USA, had a retained fishing hook from a previous capture. The hook penetrated the gastric wall and lacerated the right liver lobe. Macroscopic lesions consisted of transmural gastritis and peritonitis. Alteromonas sp. and Vibrio alginolyticus were isolated from the peritoneal fluid. In addition, a well delineated, sessile mass was found on the otherwise normal serosa of the right testis. Histopathological findings included mesothelial hyperplasia and hypertrophy involving diffusely the gastric, hepatic and parietal serosae, and forming a discrete testicular capsular mass compatible with mesothelioma. In the liver an intrahepatic cholangiocarcinoma, chronic hepatitis, biliary hyperplasia and increased numbers of melanomacrophages were found. In addition organisms compatible with histozoic and coelozoic myxosporeans were found within the skeletal muscle of the abdomen and intrahepatic bile ducts, respectively. This is the third literature report of a liver tumour and the first report of a coelomic mesothelioma from a shark.

Experience from a long-term carcinogenicity study with intraperitoneal injection of biosoluble synthetic mineral fibers

The carcinogenic potential in the intraperitoneal cavity of three newly developed biosoluble insulation glass wool fibers (M, P, and V) and one newly developed biosoluble insulation stone wool fiber (O) was investigated and compared to that of a previously developed soluble glass fiber (B). The in vitro dissolution coefficient of the three glass wool fibers ranged from 450 to 1037 ng/cm(2) x h and was 523 ng/cm(2) x h for the stone wool fiber. The in vitro dissolution coefficient of the B fiber was 580 ng/cm(2) x h. Groups of female Wistar rats (strain Crl: Wi BR) were exposed by repeated injections to doses of 0.5, 2, and 5 x 10(9) WHO fibers, which corresponds to between 41 mg to 724 mg fiber injected. In addition, 2 groups of crocidolite were used as positive controls at doses of 0.1 x 10(9) and 1 x 10(9) WHO fibers (0.5 and 5 mg). The in vitro dissolution coefficient of crocidolite is estimated to be approximately 1 ng/cm(2) x h. The protocol of the study and the size distribution of the test samples conformed to the European Commission Protocol EUR 18748 EN, and the study was executed under Good Laboratory Practice conditions. Two of the new insulation wools, fibers M and 0, showed no statistically significant tumorigenic response even at the very high dose of 5 x 10(9) WHO fibers injected. Fibers P and V showed a small tumorigenic response in the ip cavity similar in magnitude to the B fiber, which has been declared in the German fiber regulations as a noncarcinogenic fiber. The response to the soluble insulation fibers was notably different from that of the known carcinogen crocidolite, which produced 53% tumors at a comparatively low dose of 0.1 x 10(9) WHO fibers. The incidence of mesothelioma was found to be highly correlated to the incidence of intra-abdominal nodules and masses at different sites. The incidence of abdominal nodules and masses was highly correlated to the number of animals with ascites. The incidence of chronic peritonitis with fibrotic nodules at different organs also correlated with the incidence of mesotheliomas. Differences in etiology were observed between the massive doses of the highly soluble insulation wools when injected directly into the ip cavity and the lower doses of the extremely insoluble fiber crocidolite. The variability in this reaction and the impairment of animal health put into question the value of these massive doses in evaluating the carcinogenic response of soluble insulation wools. All of the fibers tested fulfilled the exoneration criteria with respect to carcinogenicity according to the European Directive 97/69/EC ("an appropriate intra-peritoneal test has not expressed signs of excessive carcinogenicity"). The dose as defined in the EC-Protocol EUR 18748 EN was 1 x 10(9) WHO fibers with a defined geometric spectrum. The influence of fiber dimensions on the ip tumor response and the difficulty in assessing the influence of the difference in background levels between this and previous studies make direct application of the German TRGS 905 criteria difficult; however, by comparison to fiber B, which in the TRGS 905 is considered as a noncarcinogenic fiber, all of the synthetic mineral fiber types tested in this study also appear to meet the intended German criteria for exoneration.

Metastatic sclerosing mesothelioma in a cow

Metastatic sclerosing mesothelioma in a crossbred cow is described. Accumulation of fluid in the abdominal cavity and solitary or coalesced nodules on the peritoneum, hepatic capsule and visceral pleurae, were observed after slaughter. Histological examination of the nodules revealed that they were composed of tubular structures supported by massive connective tissue. The lumina of the tubules were lined by solitary neoplastic mesothelial cells, or occasionally small groups of such cells were observed in the lumen. Identification of the mesothelial character of the tumours was dependent upon the histopathological and cytological characteristics of the nodules and histochemical stainings.

Juvenile malignant mesothelioma in a dog

An 11-month-old male mixed breed dog was euthanized due to two months history of vomiting and anorexia. At necropsy, numerous, multifocal or coalescing, firm, protruding nodules, 5 to 40 mm in diameter were scattered throughout the mesentery and omentum. Histologically and immunohistochemically, the nodules were diagnosed as malignant mesothelioma. Metastasis to the regional mesenteric, mediastinal and tracheobronchial lymph nodes were observed.

A peritoneal mesothelioma in a captive aardwolf (Proteles cristatus)

A 10-year-old male aardwolf (Proteles cristatus) was presented abdominal distention and emaciation for 3 months. Physical examination revealed firm abdominal masses with effusions. Cytologic assessment of the effusion showed uniform round tumor cells with a surface brush border. Necropsy showed white velvety masses covering the peritoneal surface of the liver, gall bladder, stomach, omentum, mesentery, spleen, intestine, abdominal wall and diaphragm. Histologic examination demonstrated papillary projections, lined with cuboidal tumor cells supported by fibrous connective tissue cores, arising from the serosa of visceral organs. Cytoplasmic vacuolation and a surface brush border were evident on some cells under light microscopy. Tumor cells stained positive for both cytokeratin (AE1/AE3) and vimentin. Electron microscopy showed prominent surface microvilli, rough endoplasmic reticulum, mitochondria and desmosomes in tumor cells. This may be the first reported case of peritoneal mesothelioma in a captive wild aardwolf.

Observations on ascites in nine cattle

Signs of ascites were observed in only nine of 1863 cattle examined over a period of five years. The ascites was most commonly associated with either primary or secondary cardiac disease; cattle with ascites have a poor prognosis because the condition is usually assocaited with terminal disease. Two animals had cor pulmonale with chronic pneumonia, three had cardiomyopathy, one had bacterial endocarditis, two had thrombosis of the caudal vena cava and one had diffuse abdominal epithelioid mesothelioma.

Idiopathic or mesothelioma-related pericardial effusion: clinical findings and survival in 17 dogs studied retrospectively

This retrospective study compares the clinical signs and diagnostic findings of 17 canine patients with histopathological diagnoses of idiopathic pericardial effusion (IPE) or pericardial mesothelioma (MS) in order to identify differences in clinical findings or survival times that might aid in premortem differentiation of these disease conditions. Based on this series of cases, clinical signs, physical examination findings and results of non-invasive diagnostic testing are insufficient to differentiate MS from IPE with confidence unless a discrete pericardial or intrapericardial mass can be identified. Surgical biopsy may be misleading if large amounts of highly reactive and invasive mesothelial cells are seen. Recurrence of significant amounts of pleural effusion within 120 days of pericardiectomy may increase the likelihood that MS is the cause of pericardial effusion in cases in which other causes have been excluded. Survival longer than 120 days postpericardiectomy without chemotherapeutic intervention is associated with a decreased probability of the condition being MS.

Pericardial mesothelioma in a dog: long-term survival after pericardiectomy in combination with chemotherapy

A six-year-old male crossbred dog was presented with clinical signs of right-sided heart failure. Echocardiography demonstrated a pericardial effusion with cardiac tamponade, while pericardiocentesis and cytology did not reveal any evidence of malignancy. Pericardial drainage was performed twice over a period of three months to resolve haemodynamic impairment before a subtotal pericardiectomy was performed. Biopsy of parietal and visceral pericardium confirmed the diagnosis of pericardial mesothelioma. Intrathoracic cisplatin combined with intravenous doxorubicin were administered, although neutropenia, mild azotaemia and alopecia were noted as adverse reactions to these drugs. Intravenous cisplatin was repeated 45 days later after the signs of nephrotoxicity had resolved. The dog was still free of disease after 27 months. Intrathoracic chemotherapy after pericardiectomy and early diagnosis are recommended to improve prognosis, having achieved long-term survival in the present case.

Spontaneous pericardial mesothelioma in a rhesus monkey

Spontaneous tumors in nonhuman primates are of great importance. A spontaneous pericardial mesothelioma was observed in an 18-year-old female rhesus monkey. Grossly, the visceral pericardium was multifocally irregular and thickened with tan discoloration and was soft in consistency. Histologically, the pericardium contained highly in-folded branching fronds lined by a single layer of cuboidal cells. Tumor invaded into approximately half of the thickness of the atrial and ventricular muscles. Tumor penetration was not observed into the atrial or ventricular cavity. Within the myocardium, neoplastic cells formed glandular structures which were lined by cuboidal to columnar cells. Neoplastic cells were weakly positive with PAS and strongly positive for colloid iron and alcian blue. Immunohistochemically, neoplastic cells were positive for both vimentin and cytokeratin and negative with CEA and Leu-M1, indicating mesothelial origin. To the best of the authors' knowledge, this is the first report of a spontaneous pericardial mesothelioma in a rhesus monkey.

Morphological variations in transplanted tumors developed by inoculation of spontaneous mesothelioma cell lines derived from F344 rats

Morphological and immunohistochemical features of the abdominal mesotheliomas that were developed by inoculation of 3 cell lines (MeET-4, -5 and -6) established from spontaneous abdominal mesotheliomas in male F344 rats. Although the original tumors of three cell lines showed signs of epithelioid growth with a predominantly simple papillary pattern, transplanted tumors revealed a variety of morphologic features including epithelioid with glandular structures, sarcomatous, and a mixture of these components. All tumor cells of transplanted tumors were positive for alpha-smooth muscle actin (ASMA) but almost negative for desmin as were epithelioid cells of the original tumors, and the cell lines were positive for desmin but not for ASMA. These results suggested that mesothelioma in the F344 rat had the potential for wide spectrum differentiation under in vitro conditions. The microenvironmental factors obtained in vivo can modify their potential ability and their morphological aspects. These factors may be related to tumor cell reexpression of ASMA of tumor cells that were masked under in vitro culture conditions.

Analysis of prognostic indicators for dogs with pericardial effusion: 46 cases (1985-1996)

OBJECTIVE

To determine factors associated with disease-free interval and survival time for dogs with pericardial effusion.

DESIGN

Retrospective study.

ANIMALS

46 dogs.

PROCEDURE

Signalment, history, results of physical examination, electrocardiography, echocardiography, and thoracic radiography; disease-free interval; and survival time were obtained from medical records or telephone conversations with owners and referring veterinarians.

RESULTS

Dogs that had ascites at the time of the initial physical examination were significantly less likely, and dogs that had evidence of pulmonary metastases on thoracic radiographs or that had echocardiographic evidence of a right atrial mass were significantly more likely, to have died of pericardial effusion or the underlying cause of effusion than were dogs that did not. Median survival time was 15.3 months for dogs with idiopathic pericardial effusion, 16 days for dogs with hemangiosarcoma, and 13.6 months for dogs with mesothelioma. Dogs that had a nonspecific extracardiac mass and underwent pericardiectomy were significantly less likely to have had recurrence of signs than were dogs that did not. However, dogs with mesothelioma or hemangiosarcoma that underwent pericardiectomy did not have a significantly different risk of recurrence of signs or survival time, compared with dogs that did not.

CLINICAL IMPLICATIONS

Results suggest that pericardiectomy will not affect risk of recurrence or survival time in dogs with pericardial effusion secondary to hemangiosarcoma or mesothelioma. However, pericardiectomy is still needed to differentiate dogs with neoplastic pericardial effusion from dogs with idiopathic pericardial effusion.

Metastatic malignant mesothelioma in a tiger (Panthera tigris)

An 8-yr-old female tiger (Panthera tigris) died following a 2-wk history of progressive depression, anorexia, respiratory insufficiency, and exercise intolerance. At the time of necropsy, numerous coalescing, 4-20-mm, tan, firm nodules were scattered throughout the pleural surfaces of the thoracic wall and the mediastinum, giving a velvety appearance to these surfaces. Histologically, the nodules were diagnosed as malignant pleural mesothelioma. Secondary metastasis to the regional tracheobronchial and mediastinal lymph nodes was observed.

[Hemorrhagic pericardial effusion in dogs. A retrospective study of 10 cases (1989-1994) with a review of the literature]

After an introduction on pathophysiological and etiological aspects of idiopathic hemorrhagic pericardial effusion, ten dogs affected with this condition are described. Clinical signs permitted to establish a diagnosis of suspicion in all cases. Electrocardiography, thoracic radiography and echocardiography allowed confirmation of the diagnosis. Echocardiography was the most sensitive method available. Six dogs had idiopathic pericardial effusion. A subtotal pericardectomy was performed in two of these dogs. In four dogs, the effusion was caused by a tumor. Two dogs with mesothelioma were euthanized because of poor prognosis. Heart base tumors were found in the two other dogs. One of them is still alive and well one year after subtotal pericardectomy. The other one was euthanized due to deterioration of his condition two years after the operation. Idiopathic hemorrhagic pericardial effusion carries a good prognosis if appropriately treated (pericardiocentesis, possibly subtotal pericardectomy). Pericardial effusion is also frequently associated with tumors. In such cases, prognosis and therapy essentially depend on the type of tumor.