Key Takeaways
- Grading mesothelioma — assessing the aggressiveness of cancer cells — is critical for determining prognosis and selecting the best treatment plan. It is distinct from staging, which measures how far the cancer has spread.
- The original grading system for epithelioid mesothelioma was a three-tiered scale (grades 1–3) based on nuclear atypia (how abnormal the cells look) and mitotic count (how fast they’re dividing).
- Experts now recommend a two-tiered grading system — low grade and high grade — that factors in the presence or absence of necrosis (tissue death within the tumor).
- Necrosis significantly affects survival: a 2018 study showed patients without necrosis survived a median of 19 months, compared to only 10 months for patients with necrosis.
- In the two-tiered system: low grade includes former grades 1 and 2 without necrosis. High grade includes grade 2 with necrosis and all grade 3 cases regardless of necrosis.
- The two-tiered system has been endorsed by expert pathologists and pulmonologists but has not yet been widely tested in clinical settings, and it currently only applies to epithelioid mesothelioma — not sarcomatoid or biphasic.
Mesothelioma is a rare form of cancer caused by exposure to asbestos. Grading mesothelioma is important to determine the severity of the cancer along with the best possible treatment options. Originally, the grading system for epithelioid mesothelioma was a three-tiered system. However, there is a new recommended two-tiered grading system that would be combined with the current one. This considers whether necrosis is present or not. Necrosis is a medical term meaning the death of the tissues within the body. This new way of grading mesothelioma could be helpful for future prognosis and could influence future grading systems.
There are three subtypes of mesothelioma. It is vital in terms of prognosis to know which category you fall into as a patient. The three subtypes of mesothelioma are:
- Epithelioid
- Sarcomatoid
- Biphasic
Staging Mesothelioma Using TNM
The TNM staging system for mesothelioma considers three different aspects:
- Tumor
- Nodes
- Nodule
The three-tiered way of grading mesothelioma was composed of a nuclear grade, based on nuclear atypia and mitotic count. Based on these counts, the patient was graded from a scale of one to three, which helped determine a reliable prognosis.
Necrosis
Necrosis seems to also play a role in the survival rates of mesothelioma patients, which is why a way of grading mesothelioma while factoring in necrosis may be beneficial. For instance, a 2018 study showed that the survival of mesothelioma patients without necrosis was 19 months, while the survival of patients with necrosis was only 10 months.
The Journal of Thoracic Oncology endorsed reporting of the nuclear grading system when it comes to epithelioid mesothelioma, however the experts believed that a two-tiered approach to grading mesothelioma was better than the three-tiered approach. With this two-tiered approach epithelioid mesothelioma is split into two categories: low and high grade. This combines the two grading systems because the low-grade cases would include mesotheliomas that would have previously been labeled as grade one or two, in which necrosis is not present. The high-grade mesothelioma cases would include those who are grades two and three if necrosis is present along with all other grade three cases, even if there is no necrosis.
Shortcomings of New Approach to Grading Mesothelioma
Although this two-tiered grading system is recommended by experts, it does have some shortcomings. The three-tiered grading system was heavily studied and tested for its application, while the two-tiered way of grading mesothelioma was not tested as much, specifically in a clinical setting. Also, although this new system has been endorsed by pathologists and pulmonologists that are experts in the field of diagnosing epithelioid mesothelioma, there is not a consensus among moderate pathologists that this system should be used.
Although pleural mesothelioma is by far the most diagnosed type of mesothelioma, there are other forms of the cancer as well. Pericardial mesothelioma begins in the abdominal cavity and affects approximately 10-20% of all mesothelioma patients. The grading system has not considered these patients.
Other Ideas for Grading Mesothelioma
There are other grading systems that have been proposed that take into account both epithelioid and non-epithelioid mesothelioma, but many experts believe that there is not enough data on non-epithelioid mesothelioma cases to come up with a proper grading system for this type of mesothelioma.
In conclusion, the two-tiered grading system could be a better approach to grading mesothelioma than the one that is currently in place, to determine a proper prognosis and to ensure that the patient receives the best possible treatment. This new approach can be used to inform experts on an even better grading system in the future.
If you or a loved one has been diagnosed with mesothelioma or another asbestos-related disease, we can help. Our website is filled with information about mesothelioma treatment centers in Pennsylvania, jobs in which asbestos exposure was very common, legal help, and more. For more information, call us today at (800) 505-6000 or fill out our simple contact form.
Frequently Asked Questions
What is mesothelioma grading?
Grading measures the aggressiveness of cancer cells — how abnormal they look under a microscope and how quickly they are dividing. It is different from staging, which measures how far the cancer has spread through the body. Grading helps doctors predict how the cancer is likely to behave and which treatments may be most effective. Higher-grade tumors tend to grow faster and be more difficult to treat.
What is the difference between grading and staging?
The two systems measure different things:
- Grading — assesses how abnormal the cancer cells are and how quickly they are dividing. Determined through microscopic analysis of biopsy tissue.
- Staging (TNM) — assesses how far the cancer has spread, based on the size of the Tumor, whether it has reached nearby Nodes (lymph nodes), and whether it has Metastasized (spread to distant sites). Determined through imaging tests.
Both grading and staging are used together to develop the most accurate prognosis and treatment plan.
What is the new two-tiered grading system?
The recommended two-tiered system simplifies grading into two categories:
- Low grade — includes tumors that would have been classified as grade 1 or grade 2 under the old system, where necrosis is not present
- High grade — includes grade 2 tumors with necrosis present, plus all grade 3 tumors regardless of necrosis status
This approach integrates necrosis — which is a significant predictor of survival — into the grading system, giving doctors a more accurate prognostic tool.
What is necrosis and why does it matter for mesothelioma?
Necrosis is the death of tissue within the body — in the context of mesothelioma, it refers to areas of dead tissue within the tumor itself. Necrosis is a significant prognostic indicator: a 2018 study found that mesothelioma patients without necrosis survived a median of 19 months, while those with necrosis survived only 10 months. The presence of necrosis suggests a more aggressive, rapidly growing tumor — which is why the new grading system factors it into the grade classification.
Does the new grading system apply to all types of mesothelioma?
No — currently it only applies to epithelioid mesothelioma. The two-tiered grading system was developed specifically for epithelioid cases, which account for 50–70% of all mesothelioma diagnoses. Experts acknowledge that grading systems for sarcomatoid and biphasic mesothelioma are also needed, but there is not yet enough data on non-epithelioid cases to develop a validated system. Some alternative grading frameworks that account for all three subtypes have been proposed but have not reached consensus.
Why does grading matter for treatment decisions?
Grading directly influences treatment planning because it tells doctors how aggressively the cancer is behaving at the cellular level. A low-grade epithelioid tumor (slow-growing, no necrosis) may respond well to surgery and chemotherapy, while a high-grade tumor (fast-growing, with necrosis) may require a more aggressive or different therapeutic approach. Accurate grading — combined with staging and cell subtype identification — gives the medical team the most complete picture possible for developing an individualized treatment plan.
What should I do if I’ve been diagnosed with mesothelioma?
If you or a loved one has been diagnosed with mesothelioma, ask your oncologist about both the grade and stage of your cancer — these details directly affect your prognosis and treatment options. For information about your legal options, call (800) 505-6000 or fill out our contact form for a free consultation.
