Cleyber J. Trindade de Fátima1, José C. de Almeida Souza2, Adony Q. Andrade Neto1, Jomel F. dos Santos1, Jobson Filipe P. Cajueiro3, Rodolfo José C. Souto3, Luiz T. Coutinho3, Carla L. de Mendonça3, Paula C. de Abreu e Lima4, José A. Bastos Afonso3*
1Post Graduation Student of Ruminants Sanitation and Reproduction program, at Unidade Acadêmica de Garanhuns/Clinica de bovinos, Universidade Federal Rural do Pernambuco, UFRPE, Garanhuns, PE, Brasil.
2Unidade Acadêmica de Garanhuns, UFRPE, Garanhuns, PE, Brasil.
3Clínica de Bovinos, Campus Garanhuns, UFRPE, Garanhuns, PE, Brasil.
4Laboratório de Patologia Adonis Carvalho, Recife, PE, Brasil.
Corresponding author: José A. Bastos Afonso, Clínica de Bovinos, Campus Garanhuns, UFRPE, Av. Bom Pastor, s/n. Caixa postal 152, bairro Boa Vista. Cep 55292901, Garanhuns, PE, Brasil. Phone +55 87 37613233 Email: email@example.com
Despite its rare occurrence, mesothelioma is the principal primary neoplasm of the abdominal cavity. The aim of this report was to describe a case of mesothelioma in a 10-year-old cow (breed: girolando) examined at the Garanhuns Bovine Clinic of the Rural Federal University of Pernambuco (northeastern Brazil) using clinical, laboratory and ultrasound exams as well as the pathological aspects of the disease. During the clinical examination, the animal remained predominantly recumbent, with bilateral distension (due to ascites) and ruminal hypomotility. Rectal palpation revealed rough, nodular structures in the peritoneum. The blood analysis revealed normocytic, normochromic anemia. The peritoneal fluid contained erythrocytes and mesothelial cells. The ultrasound examination revealed a large amount of hypoechoic fluid as well as a rough, irregular appearance on the surface of the omentum and spleen. Necropsy confirmed the large amount of peritoneal fluid and diffuse firm nodules (approximately 1 cm in diameter) throughout the serous membranes of the omentum, liver and spleen as well as in the mesenteric region and on the abdominal face of diaphragm. The histopathological analysis revealed epithelioid and spindle cells in a papillary format. The combination of ultrasound and abdominocentesis was important to establishing the prognosis and diagnosis of neoplasm suspicion, which was confirmed by immunohistochemistry.
Given the importance and frequency of abdominal disturbances seen at bovine clinics, including zoonotic forms, it is essential to investigate non-inflammatory, multi-systemic diseases, such as mesothelioma, which is the most important primary neoplasm of the abdominal cavity that can occur in mammals, such as bovines, dogs, equines, caprines and bubalines (5, 11). Some papers report congenital mesotheliomas in newborn cattle (10).
Mesothelioma can be either benign or malignant. However, only the malignant form has effusion. The benign form is rare and some pathologists call these tumors potentially malignant (20). In humans, 85% of cases are correlated with asbestos exposure, but cases may also be correlated with abdominal radiotherapy or tuberculosis and other chronic peritoneal infections (8). The cause of mesotheliomas in bovines remains unknown and such occurrences are rare (12). However, it is believed that the association with asbestos can also occur (12, 25).
Affected cattle often exhibit non-specific signs, such as weight loss, a decreased growth rate or milk yield, severe abdominal distension and a pear-shaped abdomen when viewed from behind. This distension is due to the accumulation of large amounts of cavity and interstitial liquid, resulting in ascites, hydrothorax, cardiac tamponade, respiratory distress and death (11). It is also difficult to determine the cytological differentiation between reactive mesothelial cells derived from inflammatory action or a neoplasm (20).
Mesothelioma is often associated with turbid effusion or stained with blood. Thus, peritoneal fluid cytology is usually the first diagnostic method performed. The fluid generally has viscous, gelatinous characteristics due to the presence of hyaluronic acid. Effusion is associated with blocked lymphatic vessels (4, 20).
Most cases of mesothelioma are diagnosed postmortem and are macroscopically characterized by multiple nodules or papilliform formations distributed diffusely on surfaces of serous membranes as well as in the parietal peritoneum. A mesothelioma can be multi-centric and progresses through extension and implementation (10). Thus, this type of tumor can also occur in the pleural cavity and, more rarely, in the pericardial sac and can even involve all cavities simultaneously. In cattle, such tumors are primarily peritoneal and then spread to other cavities (22).
Histologically, a mesothelioma can be fibromatous, epithelioid or mixed biphasic. The fibromatous form follows the shape of fibromas and fibrosarcomas and the epithelioid form should be differentiated from adenocarcinoma (11). The epithelioid and biphasic forms are more common in dogs, cats and horses, whereas the epithelioid form is more often described in cattle (20). However, Braun et al. (6) described a biphasic case with cyst formation in bovine. A common immunohistochemistry diagnosis is by the use of mouse monoclonal antibody for Wilms tumor (WT-1), this technique identify the tissue with presence of antigens associated with neoplasms, including mesothelioma (18).
The aim of this paper was to report the clinical, ultrasonographic and pathological aspects of a cow affected by mesothelioma.
A 10-year-old girolando cow from the municipality of Jucati in the state of Pernambuco (northeastern Brazil) was examined at the Garanhuns Bovine Clinic of the Rural Federal University of Pernambuco. The animal had been raised in an extensive system and was reported to be a unique case on the property.
Anamnesis revealed that the cow had experienced vaginal prolapse one day and was seen recumbent and being bitten by dogs the next day, without getting up by itself. The animal had fed on native pasture and received common salt. It was also seven months pregnant and had last given birth normally.
The animal was submitted to complete clinical examination based on Dirksen et al. (9). During the examination the cow remained in recumbent (sternal/lateral), rising only with assistance (Figure 1). The body score was 2.5. The animal had a middling appetite and exhibited pale pinkish eye mucus, dehydration (8%), mucous secretion in both nostrils, a respiratory rate of 30 breaths per minute and a heart rate of 100 beats per minute. The ventral abdomen bulged bilaterally, with liquid noted on ballottement. The rumen presented undefined stratification and decreased peristalsis. The abomasum and intestines also exhibited low motility. A wound with necrotic tissue was found in the left vulvar region.
Rectal palpation revealed multiple firm, rough structures of varying sizes (0.5 to 3 cm), some close to peritoneum and not painful upon palpation. Given the clinical findings, hemogram, ultrasonography, abdominocentesis and peritoneal fluid analysis were requested (14). The serum and peritoneal fluid were also subjected to ion analysis (9180 Electrolyte Analyzer, Roche®).
The hemogram revealed normocytic, normochromic anemia. The total leukocyte count was within the normal range, but lymphopenia and neutrophilia with left shift were found, along with hypoproteinemia, hypoalbuminemia and increased globulin levels (Table 1).
The abdominal fluid was a yellow pinkish liquid with a slightly increased density, containing 1450 cells/uL, with a predominance of monocytes (70%). Mesothelial cells and a large number of red blood cells were also found. The physical, chemical and cytological aspects classified this fluid as a transudate (Table 2).
Blood serum and peritoneal fluid ionograms were performed (Table 3). The blood ionogram results were 110 mmol/L of Na, 4.5 mmol/L of K and 1.13 mmol/l Ca++. The peritoneal fluid had 94 mmol/L of Na, 4.3 mmol L of K and 1.02 mmol l Ca++.
Ultrasound of the thoracic and abdominal cavities was performed following the technique described by Braun et al. (2, 3). It revealed large amounts of hypoechoic liquid in the abdominal cavity, suggested by the fact that pre-stomachs were at a distance of 12 to 19 cm from the abdominal wall. The surface of the spleen was irregular due to the presence of nodules. The greater omentum was floating in peritoneal fluid and also contained multiple nodules. A large amount of fluid was found in the thoracic cavity.
Due to the poor prognosis and the impossibility of treatment, the cow was euthanized and submitted to necropsy with the owner’s consent (16). The organ fragments collected during necropsy were fixed in 10% buffered formalin, processed routinely and stained with hematoxylin-eosin (HE) for histopathological analysis. Selected slides were sent for immunohistochemical analysis with nuclear staining for Wilms tumor 1 (WT-1)1, at Adonis Carvalho Pathology laboratory, Recife, Pernambuco, Brazil.
Necropsy revealed a large amount of aqueous peritoneal fluid (± 80 L) with a yellowish pink color and an increased amount of pleural fluid (± 10 L). Numerous firm nodules of varied diameters (1cm to 5cm) were found in the abdominal cavity, spleen (figure 2), liver (figure 3), bladder, mesentery and abdominal face of the diaphragm. The omentum was thickened and affect by nodules (figure 4), which did not crack when cut, but had a firm consistency and were well attached to the organs.
The histopathological analysis revealed that the tumor invaded the subepithelial connective tissue and consisted of monotonous epithelioid cells with papillary architecture, oval nuclei and pale eosinophilic cytoplasm (figure 5). Scattered psammoma bodies were also found. The immunohistochemical analysis of the tumor demonstrated nuclear positivity for WT-1, confirming the diagnosis of an epithelioid type of malignant mesothelioma (figure 6).
Mesothelioma is an uncommon neoplasm in domesticated animals. Wolfe et al. (27) report only eight cases in a period of 18 years at two veterinary schools in the United States. In Brazil, mesothelioma in cattle was reported in 1975 by Nunes et al. (21) and at least four more recent cases have been described (11, 12, 17, 23). The present paper reports the first such at the Garanhuns Bovine Clinic (state of Pernambuco, northeastern Brazil).
The most evident clinical sign of this case was severe abdominal distension due to the presence of ascites, which has also been reported by other authors (6, 11, 21, 26). The accumulation of abdominal fluid may be related to excessive production by mesothelial cells as well as deficient lymphatic drainage (13). Other commonly reported symptoms are apathy and a drop in milk production, which were also found in the present case, as well as rough, nodular structures adhered to peritoneum and serous organs, as demonstrated during rectal palpation (10, 4).
Most blood count and biochemical values were within the reference pattern. The hypoproteinemia reported here has also been described in previous cases (11). A white blood cell count within the normal range has been reported previously (26). With regard to red blood cells, the cow in question exhibited normocytic, normochromic anemia. In contrast, no abnormal red cell counts have been found in previous studies (6, 11, 26), however, other factors or concomitant diseases may have contributed to this finding.
The non-inflammatory nature of mesothelioma explains the few changes in the peritoneal fluid. Despite the slightly increased density, this can be a transudate. The predominance of mononuclear cells in relation to the reduced number of neutrophils in the present case has previously been described (4). However, the presence of mesothelial cells does not confirm the diagnosis, since such cells are also found in other abdominal cavity changes (8).
Abdominal ultrasound was very useful for the diagnosis of mesothelioma, as described in previous studies involving ruminants. Besides the changes found, other authors have found irregularities and nodules on the surface of the rumen, omasum, mesentery, liver and pericardium (4, 5; 26).
The pathological findings were similar to those described by Braun et al. (4, 5, 6) and featured severe ascites as well as multiple nodules on the omentum. The severity of the tumor is due to the spreading to the lymphatic system, with the majority of nodules located in the peritoneum and omentum. However, nodules were also found on the liver, spleen and abdominal face of the diaphragm (10, 26).
The microscopic findings were the same as those reported by Braun et al. (4, 6), who described the tumor as highly vascularized tissue with epithelioid cells in cuboidal format, which varied in arrangement between papilliform and solid filament structures. Tharwat et al. (26) report similar changes and characterize mesothelioma as cuboid and columnar cells focally distributed on a fibrous septum. In the present study, psmmoma bodies were also found, which are calcified concentric laminated structures often found in human malignancies (7). Malignant epithelioid mesothelioma was confirmed in the immunohistochemical analysis by reactivity for the WT nuclear marker, which is a method of marking tumor cells similar to that used by Braun et al. (5, 6).
In the present report, the combination of ultrasound and abdominocentesis was important to establishing the diagnosis and prognosis of a cow with mesothelioma. Despite its rare occurrence, this type of tumor should be considered in the differential diagnosis for peritoneal cavity diseases in cattle, particularly those involving non-inflammatory ascites.
We would like to thank Adonis Carvalho Pathology Laboratory (Recife, Pernambuco, Brazil), especially to Maria Do Carmo Abreu e Lima and to Paula Carvalho de Abreu e Lima for collaboration on developing this case report immunohistochemistry.
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Figure 1 - Cow in recumbency with bilateral abdominal distension
Figure 2 - Spleen with irregular surface and nodules