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Mesothelioma
 How
is mesothelioma staged?
Staging
is the process of finding out how far the
cancer has spread. Staging of mesothelioma
is based on imaging studies such as
x-rays, CT scans, and MRI scans. The
treatment and outlook for patients with
mesothelioma largely depends on the stage
(extent of spread) of their cancer. Since
pleural mesothelioma occurs most
frequently and has been studied the most,
it is the only mesothelioma for which a
staging classification exists.
The
staging system most often used for
mesothelioma is the Butchart system. This
system is based mainly on the extent of
the primary tumor mass, and divides
mesotheliomas into stages I through
IV.
Butchart
Staging System
Stage
I:
Mesothelioma is present within the
right or left pleura, and may also
involve the lung, pericardium, or
diaphragm (the muscle separating the
chest from the abdomen) on the same
side.
Stage
II:
Mesothelioma invades the chest wall or
involves the esophagus (food passage
connecting the throat to the stomach),
heart, or pleura on both sides. The
lymph nodes in the chest may also be
involved.
Stage
III:
Mesothelioma has penetrated through the
diaphragm into the peritoneum (lining
of the abdominal cavity). Lymph nodes
beyond those in the chest may also be
involved.
Stage
IV:
There is evidence of distant metastases
(spread through the bloodstream to
other organs).
Another
staging system has recently been developed
by the American Joint Committee on Cancer
(AJCC). This is a TNM system, similar to
staging systems used for most other
cancers. T stands for tumor (its size and
how far it has spread to nearby organs), N
stands for spread to lymph nodes and M is
for metastasis (spread to distant organs).
In TNM staging, information about the
tumor, lymph nodes, and metastasis is
combined in a process called stage
grouping to assign a stage described by
Roman numerals from I to IV. Minor
differences exist between the AJCC TNM
staging system and the Butchart staging
system.
TNM
Staging System
Stage
I:
Mesothelioma involves the right or left
pleura. It may also have spread into
the lung, pericardium, or diaphragm on
the same side. It has not yet spread to
the lymph nodes.
Stage
II:
Mesothelioma has spread from the pleura
on one side to the nearby peribronchial
and/or hilar lymph nodes next to the
lung on the same side. It may also have
spread into the lung, pericardium, or
diaphragm on the same side.
Stage
III:
Mesothelioma has spread into the chest
wall muscle, ribs, heart, esophagus, or
other organs in the chest on the same
side as the primary tumor, with or
without spread to subcarinal and/or
mediastinal lymph nodes on the same
side as the main tumor. Subcarinal
nodes are located at the point where
the windpipe branches to the left and
right lungs. Mediastinal lymph nodes
are located in the space behind the
chest bone in front of the heart.
Mesotheliomas with the same extent of
local spread as in stage II that have
also spread to subcarinal and/or
mediastinal lymph nodes on the same
side are also included in stage
III.
Stage
IV:
Mesothelioma has spread into the lymph
nodes in the chest on the side opposite
that of the primary tumor, or directly
extends to the pleura or lung on the
opposite side, or directly extends into
the peritoneum, or directly extends
into organs in the abdominal cavity or
neck. Any mesothelioma with evidence of
distant metastases (spread to other
organs through the bloodstream) or
spread to organs beyond the chest or
abdomen is included in this
stage.
Although
the recently developed TNM classification
is the most detailed and precise, the
original Butchart staging system is still
used most often to describe the spread of
pleural mesotheliomas. Understanding these
staging systems for mesothelioma is
important both for estimating and better
understanding prognosis, and also for
assessing therapeutic options.
Prognostic
Factors:
Because
pleural mesothelioma has been better
studied than peritoneal mesothelioma we
know more about factors associated with
prognosis for pleural mesothelioma.
Younger age at diagnosis, performance
status (functional status) and absence of
weight loss are associated with a more
favorable prognosis.
Mesotheliomas
are usually of three different cell types
(histological analysis): 1) epithelial
cell type - has the most favorable
prognosis; 2) fibrosarcomatous cell type -
carries the worst prognosis and 3) mixed
cell type - has an intermediate
prognosis.
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