Metastasis and progression of mesothelioma are often aggressive and rapid.[1] Patients diagnosed with stage IV, or metastatic mesothelioma, have limited treatment options and face a very poor prognosis.
What Is Mesothelioma Metastasis?
Metastasis occurs when cancer spreads from its primary location to more distant parts of the body. Metastatic mesothelioma usually spreads through the lymph nodes and may invade several organs and tissues.
Metastasis usually happens in stage 4 of mesothelioma, the latest stage of the disease. Metastasis is difficult to treat and typically terminal.
How Does Mesothelioma Progress?
Doctors stage mesothelioma using the TNM system. The cancer can be assigned stage I, II, III, or IV. Each stage describes how far the original tumor has invaded, whether the cancer involves lymph nodes, and whether it has progressed to metastasis.
Staging is associated with prognosis and allows doctors to assess the extent of the disease.[2]
Progression may be different for each patient but generally follows a similar course:[2][3]
- The tumor begins in the pleura on one side of the chest cavity, either the pleura lining the lung or the pleura that lines the chest wall.
- From there, the original tumor may grow into the pleura around the lungs or lining the chest wall, the diaphragm, or the area between the lungs, known as the pleural space.
- As mesothelioma continues to invade, it can eventually reach the lymph nodes, usually those on the same side of the chest as the tumor.
- The cells also spread to more distant lymph nodes. The lymph nodes are a network of immune system cells that circulate lymph through the whole body.
- When cancer spreads to the lymph nodes, metastasis is usually not far behind because the lymphatic system allows cancer cells to travel to more distant parts of the body.
How Quickly Does Mesothelioma Progress?
Mesothelioma has a long latency period—the time between asbestos exposure and symptoms of the disease. This is why many people don’t receive a diagnosis until the cancer is in later stages.
Mesothelioma progresses quickly once symptoms begin. Metastasis may occur as soon as within several weeks of diagnosis. Compared to other types of cancer, it is generally aggressive and quick-moving.
Factors Affecting Progression
However, mesothelioma can also progress at different rates based on the original cell type. Malignant mesothelioma tumors have three main cell types: epithelial, sarcomatoid, and biphasic, a mixture of epithelial and sarcomatoid cells.[4]
Sarcomatoid mesothelioma is the most aggressive and will metastasize and progress rapidly. These cells do not adhere firmly to each other and can easily break off from the tumor and spread.
Epithelial mesothelioma is the most common, and these cancer cells cling more strongly to each other, so metastasis is slower with this type of mesothelioma. Biphasic tumors fall in between the two.[4]
What Happens in the Final Stage of Mesothelioma?
In late-stage, or stage 4, mesothelioma, the cancer has typically spread throughout the chest cavity or abdomen and into lymph nodes.
The main characteristic of this late stage is metastasis. This means the cancer has spread from its original location to more distant tissues and organs in the body. It metastasizes by invading nearby tissue and moving through the bloodstream via the lymph nodes.
Late-state, metastatic mesothelioma causes additional and worse symptoms: pain, difficulty breathing, coughing, fatigue, weakness, weight loss, and fever. Many patients have significant pain at the sites of metastasis.
Where Does Pleural Mesothelioma Metastasize?
Pleural mesothelioma, which attacks the tissue lining in the chest cavity, is the most common site of occurrence. Studies show the most common locations of metastasis include:[5]
- The liver
- Adrenal glands
- Kidneys
- The lung on the opposite side of the chest
Although less common, there have been instances of pleural mesothelioma metastasizing to the brain or spinal cord, bones, and one case of recorded metastasis to the tongue.[6]
Where Does Peritoneal Mesothelioma Metastasize?
Peritoneal mesothelioma, the second most common form, begins in the tissue lining the abdominal cavity. Early progression of this cancer may see it spread throughout the abdomen, but distant metastasis only occurs later and outside the abdomen.
Some metastatic sites include the liver, heart, lungs, adrenal glands, kidneys, thyroid, bones, brain, and skin.[7]
Pericardial and Testicular Mesothelioma Metastasis
Mesothelioma of the pericardium around the heart is extremely rare. Information about metastasis is limited.
Pericardial mesothelioma often spreads locally to the pleura and lungs. It may metastasize to lymph nodes, lungs, and kidneys.
Testicular mesothelioma is the rarest type of all. From limited case studies, it is known to spread to lymph nodes in the groin area, the lower spine, the liver, the lungs, and the omentum, a layer of fat in the abdomen.
Mesothelioma Metastasis to the Liver
The liver is a common site of metastasis for mesothelioma.[5] It occurs in more than half of patients with metastatic mesothelioma. Some signs of secondary liver cancer include nausea, jaundice, decreased appetite, weight loss, fever, sweating, confusion, and pain in the upper right abdomen.
Treatments for liver involvement by mesothelioma most often include chemotherapy. Surgery is not often a treatment of choice once the disease has spread.
Mesothelioma Metastasis to the Heart
Metastasis to the heart lining, or pericardium, is rare. In case reports, symptoms of a secondary cardiac tumor vary significantly. It may cause shortness of breath, low blood pressure, an irregular heartbeat, pericardial effusion, or congestive heart failure.
The most common issue is fluid buildup in the sac surrounding the heart. Doctors can drain this to relieve pressure, but it often reaccumulates without additional treatment or catheter-directed drainage.[8]
Mesothelioma Metastasis to the Lung
A common site of metastasis in pleural mesothelioma is the lungs, including the lung on the opposite side of the chest from where the cancer originated. This occurs in more than one-quarter of patients with metastasis.
Peritoneal mesothelioma may also metastasize to the lungs. Symptoms include chest pain, coughing with or without blood, shortness of breath, weight loss, and weakness.
The primary treatment for these tumors typically utilizes chemotherapy. Surgery is rarely used. Radiation may also be used depending on the size and overall status of the cancer.[5]
Mesothelioma Metastasis to the Adrenal Glands
Several cases have been recorded of mesothelioma spreading to the adrenal glands.[5] It occurs in up to a third of the cases of metastasis of pleural mesothelioma, but it may also occur with peritoneal mesothelioma. The adrenal glands are paired organs that sit on top of each kidney.
Symptoms include back pain, abdominal pain, weight loss, or muscle weakness. It may also cause signs of adrenal sufficiency, a decrease in the hormones typically produced in the glands:
- Low blood pressure
- Low blood sugar
- Darkened skin
Mesothelioma Metastasis to the Kidney
Metastasis to the kidneys has been reported, especially with peritoneal mesothelioma.[5] Symptoms include blood in the urine, a mass on the side of the lower back, fatigue, lower back pain, loss of appetite and resulting weight loss, a fever, and anemia.
As this can commonly be confused with a primary cancer of the kidney, imaging scans and a biopsy can confirm whether the cancer has spread to the kidneys.
Mesothelioma Metastasis to the Thyroid
The thyroid gland in the neck secretes hormones and impacts metabolism. It is a possible site of metastasis for both peritoneal and pleural mesothelioma.
Signs of metastasis to the thyroid gland may include a lump in the throat or neck, pain in the neck, changes to the voice or hoarseness, difficulty breathing or swallowing, and a persistent cough.[9]
Mesothelioma Metastasis to the Brain
Studies show approximately 3% of mesothelioma cases result in metastasis to the central nervous system. There are many possible symptoms of metastasis to the brain, including poor balance and coordination, headaches, memory loss, changes in sensation, personality changes, new seizures, vision changes, and vomiting.
Treatment for this type of metastatic cancer usually involves radiation, consideration of a clinical trial, or best supportive care.[10]
Mesothelioma Metastasis to the Skin
Mesothelioma that spreads to distant sites in the body may cause secondary skin cancer. Cancer cells can travel through the lymphatic system or through the blood to reach the skin. The symptoms of metastasis to the skin are lesions that may appear anywhere, usually as red or pink raised masses.
A typical location is near or on the surgical scar where the primary cancer was removed. This can often occur due to cancer seeding or tracking of cancer cells during a biopsy or tube placement through the skin.[11]
How Is Metastatic Mesothelioma Treated?
Treatment options are limited for mesothelioma that has progressed to metastasis. The goals of treatment at this stage are largely palliation, although some patients also hope to extend their life expectancy:
- Chemotherapy. Chemotherapy is often the best treatment at this stage because it is systemic. The drugs circulate the body and target cancer cells. This can help slow the spread and shrink tumors.
- Radiation therapy. Radiation can target and shrink specific tumors, especially those causing pain or other significant symptoms.
- Surgery. Patients with metastasis are not good candidates for aggressive surgery, but they benefit from palliative procedures, such as draining fluid.
- Clinical trials. Many patients with late-stage mesothelioma choose to participate in clinical trials using experimental drugs and therapies. These trials include immunotherapy, gene therapy, and multimodal treatments.
Slowing the Progression of Mesothelioma
Mesothelioma is a quick and aggressive cancer that is only rarely curable. Most patients will experience a progression of the disease until it metastasizes to other sites.
Treatment options at this late stage are limited. There are, however, steps that can slow progression from the early stages of the disease:[12]
- Eating well
- Getting exercise
- Getting adequate sleep
- Quitting smoking
- Avoiding drinking
Most patients will experience the progression of the disease and metastasis that will most likely cause more symptoms, such as bowel obstructions, difficulty breathing, infections, pain, and discomfort.
Metastatic cancer can be treated with the intent of slowing its progression, but this is generally considered a palliative measure with a focus on the quality of life. Treatments like surgery, chemotherapy, medications, radiation, and other procedures improve life expectancy and symptom control.
