Mesothelioma Attorneys

TNM System


The TNM mesothelioma staging system is a widely used system for staging cancer including malignant mesothelioma. The TNM System is more complex than some cancer staging systems, using a combination of criteria to determine the four stages. TNM stands for tumor, lymph nodes, and metastasis. Mesothelioma staging is one of the most important factors your doctor will consider when recommending a course of treatment.

TNM Staging Basics

TNM involves tumor growth (T), lymph node involvement (N), and the presence or absence of metastasis (M). Metastasis is spreading to distant parts of the body. Like other mesothelioma staging systems, the TNM system has four stages. Those stages are determined by combinations of TNM scores.

  • Stage 1 – T1, N0, and M0
  • Stage 2 – T2, N0, and M0
  • Stage 3 – T1 or T2, N1 or N2, and M0; or T3, N0-2, and M0
  • Stage 4 – T4, any N, and M0; or any T, N3, and M0; or any T, any N, and M1

Stage 1

In the TNM System, stage 1 pleural mesothelioma, cancer is found in the left or right pleura lining the chest wall or diaphragm (parietal pleura). It has not affected the lymph nodes, or spread to distant parts of the body.

Stage 2

In Stage 2 mesothelioma the cancer has invaded the parietal pleura and spread to the visceral pleura, which is the layer of the pleura which covers the lungs. The cancer may have also invaded the diaphragm or the lung. It has not reached the lymph nodes or distant sites.

Stage 3

Stage 3 can consist of more than one combination of category scores. In Stage 3 there is still no metastasis, meaning the cancer has not spread to distant sites.

In one Stage 3 combination the cancer is found in the parietal pleura and may or may not have invaded the visceral pleura, the diaphragm, or the lung. The cancer has spread to the lymph nodes in the same side of the chest as the tumor.

Stage 3 pleural mesothelioma includes cancer in the right or left pleura. It may or may not involve lymph nodes in the same side of the chest as the tumor, but does not involve the lymph nodes on the opposite side of the chest or near the collar bone. The cancer must have spread to at least on of the following:

  • The space between the lungs (mediastinum)
  • First layer of chest wall
  • Single place in the deepest layers of the chest wall
  • Outer layer of the pericardium (covering around the heart)

Stage 4

There are three combinations which qualify as Stage 4 pleural mesothelioma under the TNM System.

If the cancer has spread to distant sites (metastasized), it is considered Stage 4 no matter what size the tumor is and whether or not the cancer has spread to the lymph nodes.

Whether the cancer has spread to the lymph nodes or not, and even if it has not metastasized, pleural mesothelioma is Stage 4 if it affects the left or right pleura and has invaded one or more of the following:

  • Pleura on the other side of the chest
  • The peritoneum by growing through the diaphragm
  • Deeper layers of the chest wall
  • Throughout the pericardium
  • Heart
  • Esophagus, trachea, thymus, or the blood vessels in the mediastinum
  • Spine
  • Brachial plexus