Pleural effusion secondary to thoracic metastatic mammary adenocarcinoma in a mare

A 17-year-old Quarter Horse mare was examined nearly 3 years after excision and cryotherapy of a papillary mammary gland adenocarcinoma. The mare had been used for pleasure riding since surgery, but had recently developed progressive dyspnea. The mare had clinical evidence of pleural effusion, but died before further clinical examination and treatment were instituted. Necropsy revealed deep mammary masses with similar nodules in the deep inguinal, renal, and mediastinal lymph nodes and in the lungs, pericardium, visceral and parietal pleurae, and left ovary. The masses were identified as papillary mammary gland adenocarcinoma. Large volumes of free pleural and peritoneal fluid were detected. The pleural fluid contained similar neoplastic cells that could have been readily detected by exfoliative cytologic examination had the mare survived.     

Omental fibrosarcoma in a horse

A 13-year-old Thoroughbred mare had a 2-week history of weight loss and intermittent fever. Examination of abdominal and pleural fluid revealed peritonitis and pleuritis. Ultrasonography of the ventral abdominal midline revealed an intra-abdominal mass. Exploratory celiotomy was performed, but the mass was not surgically excisable. The mare was euthanatized and necropsied. Histologically, the mass was determined to be a fibrosarcoma of omental origin.     

Resolution of chylothorax after resection of rib chondroma in a dog

A six-year-old, male dobermann was presented with a history of dyspnoea and bouts of coughing. Radiography and computed tomography of the thorax showed pleural effusion and a well-circumscribed, calcified mass of 10 cm in diameter, appearing to originate from the left first rib. Thoracocentesis revealed that the pleural fluid was chylous in nature. An incisional biopsy was performed, which gave a histological diagnosis of chondroma. Resolution of the chylothorax after en-bloc surgical removal of the tumour suggested that the rib tumour was the initiating cause of the chylothorax. Seventeen months later, rib neoplasia recurred without pleural effusion, and was removed successfully. To the authors' knowledge, rib chondroma, which is an unusual tumour in dogs, has not been previously documented as a cause of chylothorax.     

Antemortem diagnosis of cholangiocellular carcinoma in a horse.

A 10-year-old Tennessee Walking Horse gelding was admitted to the veterinary teaching hospital for evaluation of intermittent fever, lethargy, and anorexia. Initial laboratory analyses revealed anemia and hyperfibrinogenemia. Abdominocentesis and thoracentesis yielded fluid samples with high nucleated cell counts and total protein concentrations. The tentative diagnosis was nonseptic peritonitis. The horse did not improve after 4 days of antimicrobial treatment, and pitting edema of the ventral midline developed. Thoracic radiography and ultrasonography revealed consolidation of the ventral aspect of the lung fields and pleural effusion. Pleuroscopy of the right hemithorax revealed pleural effusion and a soft-tissue mass in the caudal portion of the mediastinum. Findings on biopsy of the liver and mediastinal mass led to a presumptive diagnosis of metastatic cholangiocellular carcinoma. The horse was euthanatized, and the diagnosis was confirmed at necropsy.     

Hematuria and weight loss in a mare with pancreatic adenocarcinoma.

This clinical report describes an 11-yr-old Thoroughbred mare that presented with clinical signs of weight loss and hematuria. History and clinical findings suggested the mare had neoplasia of the urogenital system. Although ultrasound-guided biopsy of the perirenal mass did not yield abnormal cells, large irregular cells were isolated from the thoracic and peritoneal fluid. At necropsy, multiple firm nodules were disseminated throughout the peritoneal cavity. Histological examination of the nodules revealed cells that were consistent with a pancreatic exocrine adenocarcinoma. This is the first report of pancreatic adenocarcinoma causing dysfunction of the urogenital system.     

Use of chemotherapy for treatment of a mixed-cell thoracic lymphoma in a horse

A 4-year-old Oldenburg mare was evaluated because of signs of lower airway disease and subsequently developed bilateral pleural effusion. Neoplastic cells were not identified in the fluid sample obtained via the initial thoracocentesis. A thoracic mass was detected radiographically, but its location prevented collection of a tissue sample. A diagnosis of lymphoma was made on the basis of results of immunophenotyping of pleural fluid specimens. Treatment of thoracic lymphoma in horses has been attempted, but there are limited data regarding chemotherapeutic-induced remission. In this horse, remission was achieved by use of a chemotherapeutic protocol consisting of administration of cytarabine, cyclophosphamide, and prednisolone. No adverse drug reactions were encountered during treatment. Immunophenotyping of cells in specimens of pleural fluid could be used to determine lymphocyte lineage and may be a useful alternative diagnostic modality when morphologic and cytologic examination of tissue specimens obtained via invasive techniques is not feasible.     

Bicavitary effusion in a horse with multicentric lymphoma

A 14-year-old Quarter Horse gelding presented for a 2-week history of increased respiratory rate, fever and weight loss. The referring veterinarian performed an ultrasonographic examination on the farm and considered a differential diagnosis of pleuritis and pleuropneumonia. On presentation, transtracheal wash showed suppurative septic inflammation with bacteria within macrophages. Thoracic ultrasonography showed increased hypoechoic fluid in the pleural and peritoneal cavities. Cytologic analysis of pleural and peritoneal fluids revealed lymphorrhagic effusion with atypical lymphocytes, suggestive of a lymphatic flow obstruction or lymphoma. Treatment consisted of drainage of the pleural fluid, anti-inflammatory agents, fluid therapy and antimicrobial therapy. Continued fluid accumulation in the thoracic cavity, tachypnoea, lack of response to pain medication and progressive lethargy resulted in the horse being subjected to euthanasia. At necropsy, bicavitary effusion was confirmed and histopathological diagnosis of multicentric lymphoma was made. Horses presenting with pleural effusion should also be evaluated for peritoneal effusion, as bicavitary effusion may indicate noninflammatory conditions such as neoplasia.     

Bilateral ovarian adenocarcinoma in a mare causing haemoperitoneum and colic

Abstract

CASE HISTORY: A 13-year-old Thoroughbred mare was presented with a history of mild colic over 3 days. This colic had acutely exacerbated and was unresponsive to analgesic treatment, and was referred to Massey University Veterinary Teaching Hospital.

CLINICAL FINDINGS: On examination the heart rate was 100 beats per minute, and mucous membranes were pale and tacky. A large mass was detected on transrectal palpation in the caudal abdomen to the left of midline. Explorative laparotomy revealed severe haemoperitoneum and several masses that were associated with the reproductive tract. The mare was then subject to euthanasia. On post-mortem examination, adjacent and attached to each ovary were soft, lobulated dark red masses up to 200 mm in diameter. Similar masses were present in the omentum and on the peritoneal surface of the diaphragm and the serosa of the spleen and liver. Histopathology revealed that the neoplastic component of the masses comprised proliferating cuboidal to columnar cells forming disorganised acini and cords separated by dense collagenous stroma. Immunohistochemistry showed the neoplastic cells were positive for cytokeratin AE1/AE3 and vimentin, but negative for cytokeratin 7 and inhibin α.

DIAGNOSIS: Bilateral ovarian adenocarcinoma with transcoelomic metastasis and terminal decompensation due to rupture of a neoplastic mass and consequent haemoperitoneum.

CLINICAL RELEVANCE: To the authors' knowledge, bilateral ovarian adenocarcinoma has not been previously reported in a horse. Ovarian adenocarcinoma should be considered when horses present with haemoperitoneum and colic. Further research is required on the immunohistochemical differentiation of adenocarcinoma of ovarian and intestinal origin in the horse.     

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.     

PLEURAL FLUID MOVEMENT

The present study was an attempt to illustrate the differences between ventrodorsal (VD) and dorsoventral (DV) radiographs that result from the movement of free pleural fluid. A volume of 25 ml/kg of normal saline was introduced into the pleural space of a normal dog, and radiographs of the thorax were produced in ventral and dorsal recumbency using a vertical (overhead) x-ray beam and a laterally directed horizontal x-ray beam. On the DV projection (ventral recumbency) the heart, cranial mediastinum, cranial lung lobes, and the ventral aspect of the diaphragm were submersed in fluid, which resulted in the loss of radiographically detectable borders. On the VD projection (dorsal recumbency) radiographic visualization of these structures was improved due to movement of the free pleural fluid away from them, toward the dependent caudodorsal aspect of the thorax. Radiographs of three dogs with spontaneous pleural effusion are presented to illustrate the differences in radiographic appearance of the thorax with pleural effusion when radiographed in DV and VD projections. The movement of fluid to the dorsocaudal thoracic cavity in dorsal recumbency caused lesions that were obscured on the DV projection to be revealed on the VD projection. the authors therefore recommend the use of the VD projection of the thorax in patients with pleural fluid when clinical status permits.     

Diagnostic challenges: Equine thoracic neoplasia

The diagnosis of thoracic neoplasia in the horse can be difficult due to the nonspecific nature of the clinical signs and their overlap with other pulmonary diseases. Haematological and serum biochemical evaluation, thoracic ultrasonography, radiography, endoscopic examination, and, where appropriate, thoracocentesis and pleural fluid cytology may all be helpful in reaching a diagnosis. Granular cell tumours are the most frequently reported primary pulmonary tumours of horses. They occur as single or multiple masses adjacent to bronchi and bronchioles, and the mass typically extends into the airway, resulting in partial or complete occlusion of the lumen. Thymic tumours are classified as benign or metastatic, based on evidence of tissue invasiveness, even though they uniformly appear benign histologically. These tumours are derived from epithelial reticular cells of the thymus and are rare in horses. Other primary thoracic neoplasms originate from various pulmonary tissues and are primarily reported as single case reports: pulmonary and bronchial carcinoma and adenocarcinoma, bronchogenic squamous cell carcinoma, bronchial myxoma, pulmonary chondrosarcoma, pulmonary leiomyosarcoma and pleuropulmonary blastoma. Clinical signs of these primary pulmonary neoplasms are dependent on the tumour type and location, but commonly include chronic cough, weight loss, anorexia, fever and respiratory difficulty; ventral oedema, pleural effusion and epistaxis are also frequently observed. Mesothelioma is a rare primary pleural tumour arising from the mesothelium of the pleura, pericardium and peritoneum. The clinical presentation in horses includes weight loss, respiratory difficulty and large volume pleural effusion. The tumour appears ultrasonographically as multiple small nodules on a thick serosal surface and pleural biopsy is diagnostic. Lymphoma is the most common haematopoietic neoplasm in horses, which can present with 4 main manifestations of lesions: mediastinal, multicentric, alimentary and cutaneous. Common clinical features include chronic weight loss, lethargy, anorexia, subcutaneous oedema, lymphadenopathy, colic, bleeding tendency and diarrhoea. Coughing and laboured respiratory effort are often apparent in individuals suffering from mediastinal masses. In such instances, pleural effusion may result in severe pulmonary atelectasis and pulmonary function is significantly compromised. Haemangiosarcoma is the second most common metastatic thoracic neoplasm in horses. Disseminated haemangiosarcoma is aggressive and rapidly progressive. The clinical presentation often includes tachypnoea, pale or icteric mucous membranes, respiratory distress, epistaxis, and subcutaneous, cutaneous or intramuscular masses. Other tumour types that metastasise to the thoracic cavity include adenocarcinoma, squamous cell carcinoma, fibrosarcoma, metastatic melanoma, mastocytoma and undifferentiated sarcoma. The clinical features of these tumours are generally nonspecific and often relate more to the primary site of tumour formation.     

IMAGING DIAGNOSIS—DORSAL MEDIASTINAL T‐CELL LYMPHOMA IN AN ALPACA

A 14‐year‐old male alpaca had refractory pleural effusion. The cause of the effusion was not apparent either radiographically or sonographically, or following a pleural fluid cytologic examination. Using computed tomographic (CT) examination, a dorsal paravertebral mass was identified and similar masses were found in the cranial mediastinum, retroperitoneal space, and adjacent to the hepatic entry of the portal vein. The histopathologic diagnosis was multicentric T‐cell lymphoma. CT examination may prove to be a valuable imaging modality in the localization and staging of neoplasia in new world camelids.     

Pleuroscopic diagnosis of disseminated hemangiosarcoma in a horse

A 7-year-old Thoroughbred mare was examined because of persistent bilateral epistaxis and respiratory distress. Evidence of bilateral pleural effusion was found during physical examination, and a large amount of serosanguineous fluid was drained from the right side of the thorax. Cytologic examination and bacteriologic culture of the transtracheal aspirate and pleural fluid did not yield evidence of sepsis. A coagulation profile was unremarkable. Radiographic and echographic changes were seen in the lung parenchyma. Pleuroscopy, with the horse standing, revealed numerous dark nodules on the pleura, diaphragm, and lung surface. On the basis of biopsy and necropsy findings, the histopathologic diagnosis was disseminated hemangiosarcoma.     

Neoplastic pleural effusion and intrathoracic metastasis of a scapular osteosarcoma in a dog: a multidisciplinary integrated diagnostic approach

A 10‐year‐old, female spayed mixed‐breed or cross‐bred dog was referred to the Small Animal Teaching Hospital of the University of Liverpool due to tachypnea, dyspnea, and pleural effusion not responding to diuretics and antibiotics. The chest was drained and cytology of the pleural fluid was consistent with a modified transudate with presence of atypical cells initially attributed to mesothelial hyperplasia and dysplasia. Computed tomography detected, in addition to the bilateral pleural effusion, diffuse pleural thickening, multiple pleural and pulmonary nodules, and a mineralized and lytic mass in the left scapula. Imaging findings were suggestive of a primary bone tumor with intrathoracic metastasis. Cytology of the left scapular and pleural masses revealed a malignant neoplasm highly suggestive of osteosarcoma. The diagnosis was confirmed by demonstration of a positive cytochemical reaction for alkaline phosphatase on prestained cytology slides. This finding prompted review of the initial interpretation of the pleural effusion cytology. The presence of neoplastic osteoblasts in the thoracic fluid was identified by a combination of cytochemistry, cell pellet immunohistochemistry, and transmission electron microscopy findings. In this report, a multidisciplinary integrated diagnostic approach was used to diagnose and confirm a neoplastic pleural effusion due to osteosarcoma metastasis in a dog.     

ULTRASONOGRAPHY AS A DIAGNOSTIC AID IN PLEURAL EFFUSION OF HORSES*

Three horses with clinical signs compatible with pleural effusion were examined with diagnostic ultrasound. In one of the three horses, confirmed septic pleural effusion was monitored with ultrasound during a successful treatment regimen. Eficacy of thoracentesis and detection of recurrence of fluid were readily determined. In the second horse, diagnosis of diffuse pleural neoplasia (lymphosarcoma) was made. In the third horse presented for pleural effusion, the effusion was documented and concurrent ascites detected with ultrasound. Carcinomatosis was found at necropsy. Ultrasound examination proved to be a sensitive, noninvasive modality useful in diagnosis and treatment of pleural effusion.     

Immunohistochemical features of canine ovarian papillary adenocarcinoma and utility of cell block technique for detecting neoplastic cells in body cavity effusions

Dogs with ovarian papillary adenocarcinoma occasionally present with ascites and/or pleural effusion. These aspirated fluids often contain a large number of cells, and distinction between neoplastic cells and activated mesothelial cells can be difficult. In this study, 7 cases of canine ovarian papillary adenocarcinoma, including 3 with ascites and pleural effusion, were immunohistochemically examined. Ovarian tumor cells were positive for cytokeratin CAM5.2 (CAM5.2), Wilms’ tumor 1 (WT-1) and progesterone receptor (PR) in all 7 cases. A metastatic lesion of the mediastinum in one case was also positive for CAM5.2, WT-1 and PR. Immunohistochemistry on cell blocks obtained from ascites and/or pleural effusion of 2 cases revealed the presence of PR-positive epithelial cells. Whereas, activated mesothelial cells in ascites or pleural effusion collected from dogs without neoplastic lesions were negative for PR. In addition, surface epithelium and subsurface epithelial structures (SES) of normal canine ovaries, that are considered to be the cell of origin for ovarian papillary adenocarcinoma, were also positive for CAM5.2, WT-1 and PR. These results indicate that, together with CAM5.2, WT-1 and PR is a useful diagnostic marker for canine ovarian papillary adenocarcinoma. Expression of PR may be associated with progesterone-dependent nature of canine ovarian papillary adenocarcinoma.     

Lymphosarcoma with urinary bladder infiltration in a horse.

A 9-year-old Thoroughbred mare was examined because of pollakiuria, hematuria, and weight loss of 3 weeks' duration. Physical examination revealed a regular cardiac rhythm with occasional premature contractions, and a soft tissue mass in the pelvic canal palpable per rectum. Microscopic examination of urine sediment revealed numerous RBC and a large population of lymphocytes and lymphoblasts with characteristics of neoplasia. Similar cells were found in peritoneal fluid obtained by abdominocentesis. The horse was euthanatized without treatment. Necropsy revealed a soft tissue mass infiltrating the bladder, vagina, and uterus. Additional masses were found in the sublumbar muscles and myocardium. The histologic diagnosis was lymphosarcoma.     

Intrapericardial neuroendocrine tumour in a dog

An 11-year-old neutered male Border Terrier presented for pericardiectomy after a nine-month history of tricavitary effusion, dyspnoea and lethargy. Transthoracic echocardiography revealed a fluid-filled structure at the heart base, starting at the mid-right ventricle and extending to the middle of the right atrium. Almost complete compression of the right atrium and the cranial vena cava was noted. Thoracic computed tomography revealed a heterogeneously enhancing and poorly marginated mass within the cranial aspect of the pericardium. A median sternotomy and subtotal pericardiectomy were performed. A non-distinct fluid-filled structure within the pericardium adhered to the epicardium was visualised. The structure was removed via marsupialisation along with extirpation of enlarged sternal lymph nodes. Histopathological examination of the sternal lymph nodes revealed expansile, well-demarcated, unencapsulated nodules of neoplastic cells consistent with a neuroendocrine tumour suspected to be thyroid in origin. After surgery, intractable pleural effusion resulted in euthanasia. Intrapericardial ectopic thyroid tumours are rarely reported in animals. The location of the mass and unusual presentation may have made it challenging for echocardiography to identify this neoplasia. Thoracic computed tomography at an earlier stage may have identified the neoplasia and potentially allowed for surgical intervention.     

Horner's Syndrome Associated with Disseminated Thoracic Melanoma in a Lipizzaner Horse

A 20-year-old gelding Lipizzaner horse was referred for onset of profuse sweating and increased heat on the right side of the head, neck, and thoracic limb. On physical examination, the horse presented tachycardia, muffled heart sounds with a pansystolic murmur, and signs of heart failure such as ventral edema, jugular distention, and pulsation. Ultrasonography examination revealed a bilateral pleural effusion and a large intrathoracic mass extending into the anterior mediastinum, which shifted the heart dorsocaudally. Thoracocentesis revealed serosanguineous fluid indicative of a melanocytic tumor. Thoracoscopy revealed a large dark mass extending into and filling the cranioventral mediastinum. The mass appearance was consistent with a melanoma, and because prognosis was poor, the owner elected euthanasia. A necropsy supported the presence of disseminated melanomas with a greater thoracic mass involving the right cervicothoracic ganglion, leading to clinical signs of sympathetic denervation.