Pleural mesothelioma in a dog

Outcome of dogs treated with chemotherapy for mesothelioma: A retrospective clinical study on 40 cases and a literature review

Mesothelioma is an uncommon cancer in dogs for which there is no established standard of care. Chemotherapy is often suggested despite no definitive proof of efficacy. The aim of this study was to evaluate the impact of chemotherapy on survival of dogs with mesothelioma. A retrospective multicentric study was carried out. To be included, dogs needed to present an evocative clinical evolution and a morphological diagnosis of mesothelioma. Exclusion of other cause of effusion and complete clinical follow-up were also required. Fourty dogs were included, 27 received chemotherapy (group 1) and 13 did not (group 2). Groups were heterogeneous regarding the proportion of animals undergoing surgery as part of their treatment (16 in group 1, 2 in group 2; p = .016) and homogeneous otherwise. Univariate analysis showed that dogs from group 1 survived significantly longer than dogs from group 2 (MST: 366 vs. 74 days; p < .001). Complete resolution of effusion after the first chemotherapy administration positively correlated with survival in group 1 (MST: 415 vs. 160 days; p < .01). All other variable tested had no significant impact on survival in univariate analysis, but dogs undergoing surgery and dogs having serous membranes' modification at medical imaging tended to survive longer. Multivariate analysis confirmed that chemotherapy was the sole variable independently associated with survival in our study (odds ratio 5.57-6.12; p < .01).

Abdominal mesothelioma in a goat

CASE HISTORY

An 8-year-old female Toggenburg goat was presented with a history of reduced appetite, ruminal tympany, and abdominal enlargement of 2 weeks' duration.

CLINICAL FINDINGS

The abdomen was markedly distended and contained a large amount of fluid, demonstrated using ultrasonography, along with echogenic masses on the ventral ruminal and reticular walls. The findings were confirmed at exploratory laparotomy, where together with excessive peritoneal fluid, numerous nodules were found blanketing the peritoneum. PATHOLOGICAL FINDINGS AND DIAGNOSIS: Numerous partially coalescing, white-grey nodules up to 3 cm in diameter covered the peritoneum. A biphasic mesothelioma consisting of epithelial and mesenchymal components was demonstrated by histopathology and immunohistochemistry.

CLINICAL RELEVANCE

Primary tumours of the peritoneum are rare and occur in many animal species. They must be differentiated from chronic granulomatous peritonitis caused by bacteria (e.g. tuberculosis or 'pearl disease'), parasites and metastatic tumours.

Equine sarcoids. A clinical and epidemiological study in relation to equine leucocyte antigens (ELA)

Associations between clinical parameters of sarcoids and the equine leucocyte antigen system (ELA) were analysed for 120 Swedish horses. Median age of affected horses was 5.2 years, and the majority presented with solitary tumors between 2 and 5 cm in diameter and ventral abdomen was a predilection site. Clinical signs first appeared at a median age of 3.5 years, and sarcoids at different locations first appeared at different ages. Lesions at different sites differed in size, and multiple tumors, early onset, long duration, and older age all had an association with large size. Clinical manifestations of sarcoids and the association between certain ELA-specificities and early onset (A5) and increased recurrence rates after surgery (W13), in addition to increased prevalence (A3W13), strengthen further that some horses are inherently predisposed to sarcoid growth. Unassociated with any clinical parameters, one third of the untreated horses became free of sarcoids due to "spontaneous" regression, perhaps as a result of immune responses against the tumors. Seventy percent of the horses were treated (mostly by excision), and large size was the main parameter promoting treatment. Excision had no significant effect on possibly remaining sarcoids. Recurrence rate after first treatment was about 35%, with the majority of tumors recurring within 4 months. Early onset, long duration, large size, and localization to distal limbs all appeared to increase risk of recurrence. Early treatment, performed under general anesthesia in recumbency which permits wide excision and measures to avoid autoinoculation, significantly reduced recurrence rates.

Metastatic malignant mesothelioma in a dog

A case of malignant mesothelioma in a 5 1/2-year-old St Bernard dog is described. The distribution of the neoplasm was to the pericardium and peritoneum and not the pleura. Distant metastases were found in the bronchial lymph node and bone marrow.

Malignant mesothelioma in urban dogs

Clinical and postmortem materials from six dogs with a diagnosis of malignant mesothelioma were studied retrospectively. The dogs were urban pets with clinical signs of malignant effusions. Two mesotheliomas were pleural, one pericardial, and one peritoneal. Both pleura and pericardium were involved in one dog, and the pleura and peritoneum in another. On gross examination at necropsy, diffuse granular or velvety plaques covering mesothelial surfaces were found in all dogs; firm discrete pleural nodules also were present in two dogs. Neither distant metastases nor areas of deep lung invasion were found. The tumors varied histologically, but the most common type was epithelial with a papillary pattern. Ultrastructurally, the neoplastic cells had prominent surface microvilli, numerous desmosomes, and tonofilaments. Lung tissue from these dogs and from control dogs was evaluated for the presence of ferruginous bodies. Asbestos bodies were found in three of five dogs with mesotheliomas but rarely were found in control dogs. As a group, the mesothelioma cases had significantly more asbestos bodies and total ferruginous bodies than controls. The clinical and morphologic appearance of canine mesothelioma is similar to human mesothelioma and also may be associated with exposure to airborne fibers.

The mesothelium and its reactions: a review

The origins, nature, and reactions of the mesothelium have intrigued investigators for over 100 years. Recently, the use of sophisticated techniques has clarified earlier impressions of its development, structure, and function. The structure of mesothelium reflects its functional properties, its long slender microvilli entrapping a layer of glycosoaminoglycans, providing a frictionless free surface between the parietal and visceral serosa. Transport requirements are met by various surface modifications and both inter- and intra-cellular mechanisms occur. The presence of stomatal openings in the mesothelial membrane has been established, and they may have a major role to play in the movement of cells to and from the serosal cavities. In addition, mesothelial cells can respond to situations of increased functional demand and during the course of inflammation, the mesothelium's fibrinolytic properties are of major importance in preventing the formation of adhesions and the enhancement of healing. Of all the unanswered questions the most significant is the nature, localization, and potentialities of mesothelial precursors. A mesodermal origin is readily acknowledged, but the healing process of damaged mesothelium is less clear. It seems probable that "mature" mesothelium is one source of cell renewal, but mesenchymal cells located in the submesothelial serosa are also strong contenders. Neoplastic mesothelium can adopt a spectrum of histological appearances, reflecting its mesodermal origins. In fact, overacceptance of this concept has erroneously led to the classification of other neoplasms arising in the serosal area as mesotheliomas. Although the ocogenic sequence is still obscure, asbestos is recognized as the major etiologic agent in malignant mesotheliomas. In 1955, Hartwell described differing impressions of the peritoneum as seen through the eyes of an anatomist, an histologist, and a surgeon. In this review on the mesothelium we have attempted to unravel some of its complexities as viewed by embryologists, electronmicroscopists, cell biologists, pathologists, and oncologists.