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Mesothelioma (Tumors of the Pleura, Peritoneum, and other Soft Tissues) in Dogs

Occurrence: very rare
Location of illness: Abdomen/pelvis, Chest

Author: Dr. med. vet. Gisa Löwe | Last modified: 06.11.2025

A mesothelioma is a rare, malignantMalignant means "cancerous" and is used to describe tumors or neoplasms that grow invasively and have the ability to metastasize. Malignant tumors can cause serious health problems in dogs and cats. tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. that occurs in dogs and primarily affects the pleuraThe pleura is a thin membrane that lines the lungs and the inside of the chest cavity. It consists of two layers: the visceral pleura, which covers the lungs, and the parietal pleura, which lines the chest wall., peritoneumThe peritoneum is a thin membrane that covers the inner surface of the abdominal cavity and the outer surface of most abdominal organs. It plays an important role in immune defense and fluid regulation in the abdominal cavity., or other soft tissues.

BASICS/CAUSES:

Mesotheliomas arise from the mesothelial cells that line the serous cavities of the body, such as the pleuraThe pleura is a thin membrane that lines the lungs and the inside of the chest cavity. It consists of two layers: the visceral pleura, which covers the lungs, and the parietal pleura, which lines the chest wall. and peritoneumThe peritoneum is a thin membrane that covers the inner surface of the abdominal cavity and the outer surface of most abdominal organs. It plays an important role in immune defense and fluid regulation in the abdominal cavity.. These cells have the task of providing a protective sliding surface that facilitates organ movements. Mesothelioma is an aggressive form of tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. characterized by uncontrolled cell growth in these tissues.

The exact causes for the occurrence of mesotheliomas in dogs are not yet fully understood. However, there is evidence that environmental factors could play a role. In humans, asbestos exposureExposure refers to the Contact with or subjection to certain substances, environmental factors, or pathogens. In veterinary medicine, this can include Contact with toxins, allergens, or infectious agents that can cause health problems in dogs and cats. is a known cause of mesotheliomas, and similar associations have also been suspected in dogs.

Genetic factors could also play a role by influencing the susceptibility to the development of tumors. An accumulation of mesothelioma cases has been observed in certain dog breeds, which could indicate a genetic predispositionA predisposition is an innate inclination or susceptibility of an organism to certain diseases or conditions. In dogs and cats, there may be a genetic predisposition to certain conditions such as hip dysplasia or certain heart diseases..

Another possible triggerA trigger is a stimulus that elicits a specific reaction or state. In veterinary medicine, this can refer to emotional responses, such as fear or aggression, or medical conditions, such as seizures in dogs and cats. is chronicChronic refers to a condition or disease that is long-lasting or permanent. Chronic diseases often develop slowly and can lead to persistent or recurring health problems over time. inflammatory conditions in the chest or abdominalThe term "abdominal" refers to anything that concerns the belly or the abdomen. It is an adjectival expression used to describe the location, symptoms, or conditions that occur in the abdominal area. cavity, which could increase the risk of developing mesotheliomas. These inflammatory conditions could be caused by repeated injuries or infections.

The most important facts at a glance

Mesotheliomas in dogs are Tumors that affect the pleuraThe pleura is a thin membrane that lines the lungs and the inside of the chest cavity. It consists of two layers: the visceral pleura, which covers the lungs, and the parietal pleura, which lines the chest wall. or peritoneumThe peritoneum is a thin membrane that covers the inner surface of the abdominal cavity and the outer surface of most abdominal organs. It plays an important role in immune defense and fluid regulation in the abdominal cavity.. The exact cause is not well understood, but unlike humans, there is no clear link to asbestos. Symptoms may include reduced resilience, AbdominalThe term "abdominal" refers to anything that concerns the belly or the abdomen. It is an adjectival expression used to describe the location, symptoms, or conditions that occur in the abdominal area. pain, loss of appetite, and breathing problems. Occasionally, RespiratoryRespiratory refers to breathing or the process of breathing. Respiratory diseases affect the respiratory tract and can impair the ability to breathe effectively. distress or fluid accumulation in the abdominalThe term "abdominal" refers to anything that concerns the belly or the abdomen. It is an adjectival expression used to describe the location, symptoms, or conditions that occur in the abdominal area. cavity occurs. DiagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. is made by clinical examination and imaging such as X-rays or ultrasoundUltrasound refers to sound waves that are above the hearing threshold of the human ear. In medicine, ultrasound is used for diagnostic imaging procedures to visualize internal organs, tissues, and blood flow., and a biopsyA biopsy is a medical procedure in which a small amount of tissue is removed from the body to be examined under a microscope for signs of disease. Biopsies can help diagnose cancer and other conditions. is often necessary to confirm the diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients.. Treatment requires a multimodal approach that may include surgery, radiation therapyRadiation therapy is the use of radiation, most often to treat cancer. It can be used to kill cancer cells or slow their growth without significantly damaging surrounding healthy tissue., and chemotherapyChemotherapy refers to the treatment of diseases, especially cancer, with chemical substances or drugs. It aims to kill cancer cells or prevent their growth, but can also affect healthy cells., with symptom relief and quality of life improvement being paramount. Early diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. can improve the prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop., but survival time is often limited. As the causes are unclear, specific preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. strategies are lacking, although minimizing exposureExposure refers to the Contact with or subjection to certain substances, environmental factors, or pathogens. In veterinary medicine, this can include Contact with toxins, allergens, or infectious agents that can cause health problems in dogs and cats. to carcinogens is recommended. Research focuses on developing better diagnostic methods and new therapies such as immunotherapy. Advances in imaging and the identification of biomarkers could improve early detection. An interdisciplinary approach is crucial to improving the quality of life of affected dogs and developing new treatment options.

Causes

The exact cause of mesotheliomas is not well understood in dogs. In humans, an association with asbestos exposureExposure refers to the Contact with or subjection to certain substances, environmental factors, or pathogens. In veterinary medicine, this can include Contact with toxins, allergens, or infectious agents that can cause health problems in dogs and cats. is discussed, but this is less clearly defined for dogs.

Symptoms

Very common symptoms:

Common symptoms:

Rare symptoms:

The symptoms of a mesothelioma in dogs can vary depending on which tissue is affected. However, general symptoms are often non-specific and can pose a challenge in diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients..

In the case of a mesothelioma of the pleuraThe pleura is a thin membrane that lines the lungs and the inside of the chest cavity. It consists of two layers: the visceral pleura, which covers the lungs, and the parietal pleura, which lines the chest wall., RespiratoryRespiratory refers to breathing or the process of breathing. Respiratory diseases affect the respiratory tract and can impair the ability to breathe effectively. distress, Cough, or a reduced resilience can occur, as fluid can accumulate in the chest cavity, which is referred to as pleural effusion.

A mesothelioma of the peritoneumThe peritoneum is a thin membrane that covers the inner surface of the abdominal cavity and the outer surface of most abdominal organs. It plays an important role in immune defense and fluid regulation in the abdominal cavity. can lead to symptoms such as AbdominalThe term “abdominal” refers to anything that concerns the belly or the abdomen. It is an adjectival expression used to describe the location, symptoms, or conditions that occur in the abdominal area. pain, Vomiting, DiarrheaDiarrhea refers to the condition of frequent, watery bowel movements, which can be a sign of infections, digestive disorders, or other health problems., or a bloated abdomenThe abdomen, also known as the abdominal cavity, is the part of the body located between the rib cage and the pelvis. It houses several important organs, including the stomach, liver, kidneys, intestines, and spleen.. Fluid can also accumulate here, which is referred to as ascitesAscites refers to the accumulation of free fluid in the abdominal cavity, which can lead to visible abdominal distension. It can be caused by various diseases, including liver disease, cancer, or heart failure..

In advanced stages, Weight loss, loss of appetite, and general weakness can occur. These symptoms are often the result of the metabolicMetabolic refers to metabolism, i.e. the entirety of chemical processes that take place in a living organism to enable life processes. Metabolic disorders can cause a variety of Diseases in Dogs and cats. burden caused by the tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. and the associated complications.

Diagnosis

The diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. of a mesothelioma in dogs requires a careful clinical examination and the use of diagnostic imagingDiagnostic imaging includes medical procedures that create images of the inside of the body to diagnose, monitor, or treat diseases and injuries. Examples include X-ray, ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI). techniques. X-rays and ultrasoundUltrasound refers to sound waves that are above the hearing threshold of the human ear. In medicine, ultrasound is used for diagnostic imaging procedures to visualize internal organs, tissues, and blood flow. examinations are often the first steps to identify fluid accumulations or tumorous changes.

A computed tomography (CT)Computed tomography (CT) is an imaging technique that uses X-rays and computer technology to create cross-sectional images of the body. It enables a detailed view of bones, organs, and other structures and is used for the diagnosis of injuries, diseases, and for planning medical interventions. or magnetic resonance imaging (MRI)Magnetic resonance imaging is an imaging technique that uses strong magnetic fields and radio waves to create detailed images of the inside of the body. It is used in veterinary medicine to diagnose diseases of the brain, spine, and other organs. can provide more detailed information about the extent of the tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions.. These procedures are helpful to determine the exact extent of the disease and to assist in planning the treatment.

A definitive diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. usually requires a biopsyA biopsy is a medical procedure in which a small amount of tissue is removed from the body to be examined under a microscope for signs of disease. Biopsies can help diagnose cancer and other conditions., in which a tissue sample of the tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. is taken and examined microscopically. This examination can confirm whether it is a mesothelioma and what type of cells are involved.

In addition, cytological examinations of the fluid from pleural effusions or ascitesAscites refers to the accumulation of free fluid in the abdominal cavity, which can lead to visible abdominal distension. It can be caused by various diseases, including liver disease, cancer, or heart failure. can be performed to find evidence of malignantMalignant means "cancerous" and is used to describe tumors or neoplasms that grow invasively and have the ability to metastasize. Malignant tumors can cause serious health problems in dogs and cats. cells. However, these analyses are often less specific than a biopsyA biopsy is a medical procedure in which a small amount of tissue is removed from the body to be examined under a microscope for signs of disease. Biopsies can help diagnose cancer and other conditions..

Therapy

The treatment of mesotheliomas in dogs is complex and often requires a multimodal approach. Surgical interventions can be considered to remove the tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. or alleviate the symptoms, especially if the tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. is localized.

Radiation therapyRadiation therapy is the use of radiation, most often to treat cancer. It can be used to kill cancer cells or slow their growth without significantly damaging surrounding healthy tissue. can be used in some cases to reduce the tumor mass and alleviate the symptoms. However, the effectiveness depends on the location and extent of the tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions..

ChemotherapyChemotherapy refers to the treatment of diseases, especially cancer, with chemical substances or drugs. It aims to kill cancer cells or prevent their growth, but can also affect healthy cells. can also be an option, either as a sole treatment or in combination with surgery and radiation therapyRadiation therapy is the use of radiation, most often to treat cancer. It can be used to kill cancer cells or slow their growth without significantly damaging surrounding healthy tissue.. Some chemotherapeutic agents have shown that they can slow down tumor growth, but the side effects must be carefully monitored.

PalliativePalliative refers to treatments that aim to alleviate the symptoms of a disease without curing the disease itself. Palliative care focuses on improving the quality of life of patients with incurable diseases. care, which focuses on alleviating symptoms and improving the quality of life, is often an important part of the treatment plan. This includes the treatment of pleural effusions or ascitesAscites refers to the accumulation of free fluid in the abdominal cavity, which can lead to visible abdominal distension. It can be caused by various diseases, including liver disease, cancer, or heart failure. and the administration of pain relievers.

Prognosis and follow-up care

The prognosis for dogs with mesothelioma is generally guarded to poor, as it is an aggressive type of tumor that is often detected late. The survival time depends on many factors, including the tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. location, the extent at diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients., and the chosen treatment.

Dogs that are diagnosed early and receive comprehensive treatment may have a better prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop., but the medianMedian refers to the midline or center of the body or an organ. In veterinary medicine, the term can be used to describe the location of a structure in relation to the center of the body. survival time is often only a few months. Regular follow-up examinations are important to monitor the course of the disease and adjust the treatment accordingly.

Prevention

Since the exact causes of mesotheliomas in dogs are not fully understood, there are currently no specific preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. strategies. However, minimizing exposureExposure refers to the Contact with or subjection to certain substances, environmental factors, or pathogens. In veterinary medicine, this can include Contact with toxins, allergens, or infectious agents that can cause health problems in dogs and cats. to known carcinogenic substances, such as asbestos, could reduce the risk.

Regular veterinary examinations can help to detect health changes early, which increases the chances of timely diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. and treatment.

A healthy lifestyle, including a balanced diet and sufficient exercise, can contribute to the general health of the dog and potentially reduce the risk for various diseases, including Tumors.

Outlook on current research

Research on mesotheliomas in dogs has gained importance in recent years, as this type of tumor is relatively rare and difficult to diagnose. Veterinarians and researchers are focusing on better understanding the causes and developing more effective diagnostic methods. It is believed that environmental factors, genetic predispositions, and possibly exposureExposure refers to the Contact with or subjection to certain substances, environmental factors, or pathogens. In veterinary medicine, this can include Contact with toxins, allergens, or infectious agents that can cause health problems in dogs and cats. to asbestos could play a role, similar to humans. However, the connection is less clear in dogs, as they are less likely to come into direct contact with asbestos.

Some studies have focused on identifying biomarkers that could enable early detection of mesotheliomas. These biomarkers could be detected in the blood or other bodily fluids and help to diagnose the disease at an earlier stage, which could improve treatment options. The development of imaging techniques that specifically target the detection of mesotheliomas is also an active area of research. Advances in imaging could help to increase the accuracy and speed of diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients..

In terms of treatment, scientists are exploring new drug therapies as well as targeted therapies that target the molecular properties of mesotheliomas. Another promising direction is immunotherapy, which aims to strengthen the dog’s immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body. to fight tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. cells more effectively. Clinical trials are underway to evaluate the effectiveness and safety of such therapies.

An interdisciplinary approach that combines veterinary medicine, molecular biology, and oncologyOncology is the branch of medicine that deals with the diagnosis, treatment, and research of cancer. In veterinary medicine, this includes the treatment of cancers in animals. is considered crucial to making progress in the fight against mesotheliomas in dogs. Collaborations between universities, research institutions, and veterinary clinics contribute to deepening the understanding of this complex disease and developing innovative treatment approaches.

In summary, research on mesotheliomas in dogs is continuously progressing, but many questions remain open. The ongoing efforts aim to improve the quality of life and survival rates of affected dogs while gaining new insights that may also be relevant to understanding the disease in humans.

Frequently asked questions (FAQs)

What is a mesothelioma in dogs? A mesothelioma is a rare tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. that affects the mesothelium, a thin layer of tissue that lines the internal organs. In dogs, these tumors mainly occur on the pleura or peritoneumThe peritoneum is a thin membrane that covers the inner surface of the abdominal cavity and the outer surface of most abdominal organs. It plays an important role in immune defense and fluid regulation in the abdominal cavity..
What symptoms do dogs with mesotheliomas show? The symptoms can vary, but often include RespiratoryRespiratory refers to breathing or the process of breathing. Respiratory diseases affect the respiratory tract and can impair the ability to breathe effectively. distress, Cough, lethargy, Weight loss, and fluid accumulation in the chest or abdominalThe term "abdominal" refers to anything that concerns the belly or the abdomen. It is an adjectival expression used to describe the location, symptoms, or conditions that occur in the abdominal area. cavity.
How is a mesothelioma diagnosed in dogs? The diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. is usually made through a combination of clinical examinations, imaging procedures such as X-rays or ultrasoundUltrasound refers to sound waves that are above the hearing threshold of the human ear. In medicine, ultrasound is used for diagnostic imaging procedures to visualize internal organs, tissues, and blood flow., and the analysis of tissue samples (biopsy).
What are the causes of mesotheliomas in dogs? The exact causes are unclear, but it is believed that genetic factors, environmental factors, and possibly exposureExposure refers to the Contact with or subjection to certain substances, environmental factors, or pathogens. In veterinary medicine, this can include Contact with toxins, allergens, or infectious agents that can cause health problems in dogs and cats. to asbestos could play a role.
Can mesotheliomas be treated in dogs? Yes, there are various treatment options, including surgery, chemotherapyChemotherapy refers to the treatment of diseases, especially cancer, with chemical substances or drugs. It aims to kill cancer cells or prevent their growth, but can also affect healthy cells., and in some cases radiation therapyRadiation therapy is the use of radiation, most often to treat cancer. It can be used to kill cancer cells or slow their growth without significantly damaging surrounding healthy tissue.. The choice of treatment depends on the stage and location of the tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions..
What are the survival chances for dogs with mesotheliomas? The prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. is often guarded, as mesotheliomas can be aggressive. Early diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. and treatment can improve the chances of survival.
Are there preventive measures to avoid mesotheliomas in dogs? Since the exact causes are unknown, there are no specific preventive measures. However, a healthy lifestyle and regular veterinary examinations can be helpful.
Are certain dog breeds more susceptible to mesotheliomas? So far, there is no clear evidence that certain breeds are more susceptible. However, genetic factors could play a role in the development.
Can mesotheliomas in dogs be contagiousContagious means infectious. Diseases that can easily be transmitted from one animal to another or from animals to humans are referred to as contagious.? No, mesotheliomas are not contagiousContagious means infectious. Diseases that can easily be transmitted from one animal to another or from animals to humans are referred to as contagious.. It is a tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. that arises from internal factors.
What research is being conducted on mesotheliomas in dogs? The research includes the search for biomarkers, the development of new diagnostic methods and treatments, as well as the understanding of the genetic and molecular basis of the disease.