David C. Rice, MB, BChAssociate Professor of Surgery

The University of Texas, M.D. Anderson Cancer Center

Staging refers to the process of defining the anatomic extent of

a tumor. Based on extent cancers are placed into one of 4

stage groupings which encompass the spectrum from early

stage localized tumors (Stage I) to advanced stage tumors that

have spread to other organs (Stage IV). The purpose of

staging is to define groups of patients who have similar

prognosis and to guide appropriate therapy. It is essential that

cancers be properly staged prior to embarking on treatment so

that the most effective form of therapy can be delivered to the

patient. Staging that occurs based on clinical information

available prior to surgery is called clinical staging and is

generally less accurate than pathologic staging which is based

on precise anatomic information available only after the tumor

has been examined after surgery.

The most widely accepted staging system for mesothelioma is

that endorsed by the International Mesothelioma Interest

Group (IMIG) and the American Joint Commission on Cancer

(AJCC). This system defines stage according to the extent of

the tumor itself, the involvement of lymph glands (or nodes)

and the presence of metastases to other organs.

The current AJCC staging system is under evaluation and will

probably be revised within the next few years.

Other staging systems in clinical use include the Brigham and

Womens Staging System and the Butchart Staging System

In its earliest manifestation, mesothelioma appears as

multiple small white nodules that involve the thin translucent

lining of the chest wall (parietal pleura). In general there is

diffuse involvement of the pleura rather than a single discrete

focus of tumor. This stage is rarely diagnosed and may be

seen as either slight thickening of the pleura on CT scans or

as fluid accumulation between the chest wall and lung (pleural

effusion).

As tumor spreads it will involve the thin pleural lining the lung

surface (visceral pleura). The radiographic findings are similar

to Stage Ia except there may be nodularity of the pleura seen

in between the different lobes of the lung.

As tumor grows it may invade into the lung or diaphragm (the

muscle in between the chest cavity and the abdomen). CT

scan is imprecise at accurately predicting either lung or

diaphragm invasion, although in general the greater the degree

of pleural thickening and tumor bulk, the greater the chance of

lung or diaphragm invasion.

Mesothelioma may grow across the pleural lining of the chest

wall to invade into the substance of the chest wall itself. When

this occurs in a single region it denotes Stage III. The tumor

frequently invades the chest wall at the site of previous surgical

incisions. CT scan and MRI are useful for determining chest

wall invasion.

Mesothelioma can also invade into the fibrous sac that

surrounds the heart (pericardium). When there is only

superficial invasion it also denotes Stage III. Lastly,

mesothelioma, like other tumors can spread to lymph glands.

When it spreads to glands in the chest on the same side as the

tumor it denotes Stage III. Radiographic imaging (CT scan,

PET scan or MRI) is inaccurate at determining pericardial

invasion or nodal involvement.

When mesothelioma invades multiple areas of the chest wall,

invades through the pericardium or diaphragm, involves lymph

glands outside the chest or spreads to other organs it denotes

Stage IV disease. Chest wall invasion may be identified with

CT or MRI, however they are poor at determining invasion

across the diaphragm or pericardium.

PET scan is a very useful technique for determining whether

the tumor has spread outside the chest.

Your doctor may order a variety of tests to determine the stage

of your tumor. The results of these tests will help determine

which therapy will be the most appropriate for your tumor. Non-

invasive tests usually involve medical imaging or blood testing.

Invasive tests are those that involve a minor surgical procedure

or a image-guided biopsy.

Non-Invasive Tests Serum Mesothelin Measures blood levels of a protein

secreted by certain mesotheliomas.

Chest X-Ray Defines extent of tumor within the chest.

CT scan Defines extent of tumor but gives more detailed

information than chest x-ray

MRI Useful if chest wall invasion suspected on CT scan.

PET scan Very useful for determining whether tumor has

spread to other organs outside of the chest.

Non-Invasive Tests CT-guided core biopsy Diagnosis of mesothelioma.

Outpatient procedure.

Thoracentesis Outpatient evaluation of fluid from chest.

Diagnostic only 30% of the time.

Thoracoscopy The most accurate method of diagnosing

mesothelioma. Involves general anesthetic and a small incision

on the chest.

Mediastinoscopy Outpatient surgical procedure to evaluate

if lymph glands in the center of the chest contain tumor.

Involves a small incision on the neck.

Endobronchial ultrasound needle biopsy Outpatient

procedure that evaluates if lymph glands in the center of the

chest contain tumor. Does not involve surgery.

Laparoscopy Outpatient surgical procedure to evaluate if

tumor has spread to the abdomen.

Surgical Staging In patients who are deemed candidates for surgery based on

non-invasive tests, surgical staging is usually performed to

ensure that tumor does not involve the lymph glands or the

abdomen. This involves a single, short outpatient anesthetic

where laparoscopy and endobronchial ultrasound guided fine

needle aspiration are performed simultaneously. Occasionally

thoracoscopy may be required to obtain additional tumor tissue

to confirm the diagnosis of mesothelioma. In this case patients

usually stay over night in hospital and go home the following

day.