The four stages describe how far pleural mesothelioma, a cancer in the lining of the lungs, has spread. Stage 1 means it sits in that lining on one side of the chest. The lymph nodes, small glands that filter fluid, are clear. Stage 2 means a thicker tumor, or growth into nearby fat, and sometimes nodes on the same side. Stage 3 means growth into nearby structures, or nodes on the other side. Stage 4 means it has reached distant places such as the abdomen or the bones.

No. Only pleural mesothelioma, the type in the lining of the lungs, has a formal four-stage system. For peritoneal mesothelioma, which grows in the lining of the abdomen, surgeons often use the Peritoneal Cancer Index. That score runs from 0 to 39 and adds up how much tumor sits across 13 areas of the belly. A lower score points to a better outlook and a better chance that surgery is an option. Pericardial and testicular mesothelioma have no formal stages at all.

Doctors stage pleural mesothelioma with the TNM system. It rates the tumor (T), the lymph nodes (N) and spread to distant parts of the body (M). Those three ratings combine into stage 1, 2, 3 or 4. In the US, the AJCC Version 9 system applies to cases diagnosed on or after January 1, 2026. It measures tumor thickness on a CT scan. Cases diagnosed before that date were staged with the 8th edition, so an older report may look different.

Doctors work out the stage from scans and tissue samples, not from one single test. CT, PET and MRI scans show how far the tumor has spread. Doctors may also look inside the chest or abdomen with a small camera, or take a sample from lymph nodes. The stage set before surgery is called the clinical stage. If surgery is done, the tissue removed can give a more exact pathological stage. The stage recorded at diagnosis stays the same even if the cancer later grows.

Stage 2 and stage 3 both mean the cancer has grown beyond its starting point, but stage 3 has gone further. In stage 2, the tumor is thicker or has grown into the fat in the mid chest. It may also reach one spot on the chest wall, or nodes on the same side. Stage 3 means a much thicker tumor, or growth into bone, the heart sac or nearby organs. It can also mean nodes on the opposite side. Surgery may still be considered in stage 2 and some stage 3 cases.

Stage 4 mesothelioma is the most advanced stage. It means the cancer has spread to distant parts of the body. That can include the other lung, the lining of the abdomen, the bones or the liver. You may hear it called metastatic, which means the same thing. Stage 4 does not mean treatment is over. Surgery is not usually possible, so the plan shifts to slowing the cancer and keeping your loved one comfortable.

Stage 4 mesothelioma symptoms usually include worsening shortness of breath, chest or back pain, a stubborn cough, deep tiredness, poor appetite and weight loss. Fluid often builds up around the lung again after it is drained, which makes breathing harder. Some people also have trouble swallowing or a hoarse voice. Most of these symptoms can be eased, so tell the care team early. Palliative care, a team that focuses on comfort, can start at diagnosis and run alongside cancer treatment.

Survival with stage 4 mesothelioma varies widely in both directions. In the trial behind the 2024 FDA approval of pembrolizumab, an immunotherapy drug, added to chemotherapy, median survival was 17.3 months. Chemotherapy alone gave 16.1 months. A median of 17.3 months means half the people in that group lived longer than that and half lived less. Those patients had pleural mesothelioma that surgery could not remove, which is broader than stage 4 alone. It is not a prediction for your loved one.

Two immunotherapy combinations are approved in the US as first treatment when pleural mesothelioma cannot be removed by surgery. Immunotherapy helps the body's own immune system attack cancer. Nivolumab with ipilimumab was approved in 2020, and pembrolizumab added to chemotherapy was approved in 2024. Chemotherapy on its own, using pemetrexed with a platinum drug, is still an option. Which one fits depends on the cell type and your loved one's health, so ask the team what applies.

Survival is usually reported by how far the cancer had spread, not by numbered stage. For US pleural mesothelioma found from 2015 to 2021, five-year relative survival was about 23 percent for localized disease. It was 15 percent when the cancer had reached nearby tissue or lymph nodes, and 11 percent once it had spread further. Relative survival compares people with mesothelioma to people of the same age in the general population. These figures cover people diagnosed before the newest treatments were in wide use.

Mesothelioma is usually not curable, and finding it early does not change that on its own. A small number of people have disease that is still limited to one area. For them, a specialist center may give treatment aimed at long-term control. Only a specialist can say whether that applies to your loved one. What an early stage does change is the options, because surgery is usually only considered in the earlier stages. Treatment has improved, some people live for years, and trials are open.

In the final stages of mesothelioma, most people become much more tired and sleep for longer stretches. They eat and drink very little, and shortness of breath usually gets worse. Pain and confusion are common, and in the last days breathing often turns irregular and the hands and feet feel cool. This is hard to watch, but most of these symptoms can be controlled. Palliative care aims at comfort and can be given at any stage. Hospice teams manage pain and breathlessness well, often at home.

There is no exact timeline for the final stages of mesothelioma. An honest doctor will give you a range rather than a date. Hospice care, which focuses on comfort near the end of life, is offered when a doctor expects six months or less. The last weeks often bring much more sleeping and far less eating. Doctors' estimates tend to be too hopeful, so ask for a range and ask what to watch for. A palliative care team can keep most symptoms controlled throughout.

Most people are diagnosed at a later stage, after symptoms have already started. Early signs such as breathlessness, a cough or pain in the side are easily mistaken for more common problems. Most people with mesothelioma have symptoms for a few months before they get a diagnosis. There is also a long gap, often decades, between asbestos exposure and the first sign of illness. No major medical group currently recommends screening people who were exposed.

The stage tells the team whether surgery is worth considering. Surgery is only discussed in the earlier stages, and it is not right for most people. MARS 2, a trial of 335 patients, tested lung-sparing surgery added to chemotherapy. Median survival was 19.3 months, against 24.8 months for chemotherapy alone. Specialist centers still consider surgery for a few people with early disease of the epithelioid cell type, which has the best outlook. Otherwise immunotherapy or chemotherapy comes first, so ask about clinical trials and a second opinion.