Malignant Mesothelioma – Types and Stages

Malignant Mesothelioma

Charts of the types and stages of mesotheliomaBased on the primary region in the body affected, there are 4 types of malignant mesothelioma’s

  • Pericardial- affecting the pericardium in the heart
  • Peritoneal- in the abdomen
  • Pleural- in the chest, the most common.
  • Mesotheliomas of the tunica vaginalis, a layer covering the testicles.

Because not all malignant mesothelioma metastasizes, mesothelioma can be also be categorized as either localized or diffuse. \

A histological examination of a mesothelial tumor offers the following WHO- approved classification:

  • Epithelioid mesothelioma these are cancerous epithelial cells. They are the most commonly affected cells and are more responsive to medication, meaning that their prognosis is often good. More than 10 subtypes of epithelioid cells exist.
  • Sarcomatoid mesothelioma also called spindled, or fibrous mesothelioma, this is the rarest and most lethal mesothelioma. They are easily mistaken for other malignant and benign tumors, but are very aggressive, making accurate diagnosis using immunohistochemical techniques imperative.
  • Biphasic Mesothelioma Examination of cells samples from this kind of mesothelioma reveals a hybrid of Sarcomatoid and epithelioid cells.

Given all these variables in mesotheliomas, medical professionals rely on a standard system of staging the disease so that they can have a better idea of how far the disease has spread and what methods can be used to cure the condition. The most commonly used method is the TNM system, developed by the American Joint Committee on Cancer. In this system,

  • T shows the damage caused by the primary tumor
  • N describes the spread of the cancer to nearby lymph node
  • M shows whether or not the cancer has metastasized.

Letters and numbers are added to these letters to further categorize the cancer; advanced cancers have higher numbers. A combination of these values are then used to define the four stages of mesothelioma.

The TNM Classification


T- primary tumor

Tx- the primary tumor can’t be assessed

T1- tumor affects ipsilateral parietal pleura; could also be affecting visceral pleura

T1a- tumor affects ipsilateral parietal pleura only

T1b- tumor affects ipsilateral parietal pleura & visceral pleura

T2- tumor affects ipsilateral pleura and any one of these:

  •   confluent visceral pleura
  •   diaphragmatic muscle
  •   lung parenchyma

T3- ipsilateral surface affected, plus any of this:

  •   endothoracic farcia
  •   mediastinal fat
  •   soft tissues on chest wall
  •   pericardium

T4-ipsilateral surface affected, plus any of this:

  •   soft tissues in chest wall
  •   ribs
  •   diaphragm through to the peritoneum
  •   mediastinal organs
  •   contralateral pleura
  •   the spine
  • ú internal layer of pericardium
  •   pericardial effusion
  •   myocardium
  •   branchial plexus


N- regional lymph node

Nx- regional lymph can’t be assessed

N1- metastasis in ipsilateral bronchopulmonary &/or hilar node

N2- metastasis in subcarinal lymph nodes&/or ipsilateral internal mammary/ mediastinal nodes

N3- metastasis in contralateral mediastinal/ internal mammary, hilar/ ipsilateral/ contralateral supraclavicular/ scalene node.

M- distant metastasis

Mx- metastasis can’t be assessed

M0- no distant metastasis

M1-distant metastasis

Based on this information, mesothelioma can be:

  • Stage 1A- T1a, N0, M0
  • Stage 1B- T1b, N0, M0
  • Stage II-T2, N0, M0
  • Stage III- T1,T2, N1, M0 or T1,T2, N2, M0 or T3, N0, N1, N2, M0
  • Stage IV-T4, any N, M0 or Any T, N3, M0 or Any T, Any N, M1.