Mesothelioma is a rare cancer that starts in the mesothelium, the thin lining that covers organs inside the chest and belly. It can also begin in the lining around the heart or the testicles, though that is rare. Most cases are caused by breathing in or swallowing asbestos fibers, often decades earlier. About 2,700 cases were reported in the United States in 2022, the most recent year in the CDC's count. Most begin in the lining around the lungs. Treatment has improved, and real support is there.

Yes. Mesothelioma is cancer, which means it grows into nearby tissue and can spread. Since 2021 the World Health Organization has used the single word mesothelioma, because every tumor with that name counts as cancerous. You will still see the older phrase malignant mesothelioma, and it means the same thing. A few rare mesothelial growths are not cancer, such as adenomatoid tumors, and they were given separate names on purpose. A report may also say mesothelioma in situ, which means abnormal cells sit on the surface and have not grown in yet.

Mesothelioma is a cancer of the mesothelial cells that line your body's internal spaces. Doctors sort it two ways, by where it starts and by how the cells look under a microscope. Epithelioid cells look rounded and orderly, and make up about 6 in 10 cases. Sarcomatoid cells look long and spindly, about 1 in 10. Biphasic tumors hold both patterns, about 3 in 10. Those shares come from the American Cancer Society, which also notes epithelioid usually has the better outlook.

No. Mesothelioma is not lung cancer. It starts in the pleura, the thin lining around the lungs and inside the chest wall, not in the lung itself. That difference matters, because mesothelioma is staged differently, treated with different drugs and operations, and handled by different specialists. Asbestos can cause both diseases, and they can look alike on a scan. So a biopsy and special stains are used to tell them apart.

There are four main types of mesothelioma, named for where the cancer starts. Pleural mesothelioma begins in the lining around the lungs and is by far the most common. Peritoneal mesothelioma begins in the lining of the abdomen (belly). Pericardial and testicular mesothelioma, in the linings around the heart and the testicles, are both very rare. Of US cases reported from 2003 through 2022, the CDC counted 81 percent pleural and 11 percent peritoneal. Pericardial and testicular were 0.2 percent each, and about 8 percent were logged at other or unrecorded sites.

Most people who develop mesothelioma were exposed to asbestos, though not everyone can point to where or when. Exposure often happened at work, in trades like construction, shipyards, insulation, plumbing, railroads, or auto repair. Tiny fibers are breathed in or swallowed. They settle in the lining of the lungs or belly and damage those cells slowly, over decades. Family members have become ill from fibers carried home on work clothes. Other cases follow erionite, a mineral like asbestos, past radiation to the chest, or no known exposure.

Mesothelioma usually appears 20 to 50 years after a person's first asbestos exposure. That long delay is why the average age at diagnosis for mesothelioma in the chest is about 70. Mesothelioma in the belly tends to be found earlier, with most patients in their 50s. Those three figures are the American Cancer Society's. The delay is also why many people cannot recall the exposure that caused it. A job your loved one left forty years ago can still be the reason, and they could not have known.

Mesothelioma is usually not inherited, and having a relative with it does not mean you will get it. In one study of 198 patients at specialist centers, 12 percent carried an inherited change in a cancer gene. The most common was a gene called BAP1, in about 3 percent of those 198 people. Most had no inherited change at all. If a pathology report says BAP1 is lost, that describes the tumor itself, not something passed down. Ask about genetic counseling if several close relatives have had mesothelioma, or eye or skin cancers.

No. Mesothelioma is not contagious. You cannot catch it from your loved one by hugging, kissing, sharing meals, or breathing the same air. Cancer cells from one person cannot survive in another person's body. What does travel between people is asbestos dust, which is why some family members were exposed by fibers on work clothes. Being close to someone who has mesothelioma is completely safe.

The only way to know for certain if you have mesothelioma is a biopsy. A doctor removes a small piece of tissue, and a pathologist, a doctor who studies cells, examines it. The signs that lead to testing are shortness of breath, chest or side pain, and a cough that will not settle. In the belly, the signs are swelling, pain, and weight loss. Doctors usually start with a chest x-ray or CT scan. Fluid drawn from around the lung can help, but it often misses the diagnosis, so tissue is needed.

Mesothelioma is mostly hidden inside the body, so there is usually nothing to see from the outside. If you are asking because you dread what you might see, that is the honest answer. What families do sometimes notice is weight loss, or a belly that swells with fluid. On a CT scan it shows as fluid around the lung, called an effusion. The lining thickens and can wrap the lung like a rind. Under a microscope the cells look much like lung cancer, so special stains are used.

Mesothelioma is usually treated with a combination of drugs, sometimes along with surgery or radiation. Chemotherapy uses drugs that kill fast-growing cells, and immunotherapy helps the body's own immune system attack the cancer. For pleural mesothelioma that surgery cannot remove, two drug pairs are standard first treatments. One is nivolumab with ipilimumab, and the other is pembrolizumab with chemotherapy, which the FDA approved in September 2024. Which one fits your loved one depends on cell type and general health.

For most people mesothelioma is not curable. The National Cancer Institute says standard treatment for all but localized mesothelioma is generally not curative. When the disease is caught early and still limited to one area, a specialist center may aim for long-term control. Only a specialist can say whether that applies. Treatment has improved too, and clinical trials are open. In the CheckMate 743 trial of pleural mesothelioma, 14 percent on immunotherapy were alive at five years, versus 6 percent on chemotherapy.

Mesothelioma most often leads to death through breathing that slowly gets harder. As the tumor thickens the lining around the lung, the lung cannot fill and fluid gathers in the same space. In the belly the pattern is swelling and bowel trouble instead of breathlessness. Most of these symptoms can be controlled, often by draining the fluid or sealing the space. Palliative care means comfort care given alongside treatment at any stage. Hospice is comfort care near the end, and both teams treat pain and breathlessness well.

The most useful first step is to get to a cancer center that treats mesothelioma often. The disease is rare, and experience changes what is offered. Ask for a second opinion, including a second look at the biopsy slides, because mesothelioma is easy to confuse with other cancers. Ask what cell type your loved one has, and what stage, meaning how far it has spread. Ask about clinical trials, which are studies of newer treatments. Ask for palliative care early too, for comfort alongside treatment.