Before discussing the staging, let’s have a look at the normal anatomy of esophagus that will help to understand the staging better.
Normal Anatomy of Esophagus explained with Video and Images
In the chest cavity, this trachea lies in front which helps us breathing.
As you can see, behind the trachea lies the esophagus.
Heart also lies in the chest cavity in front of esophagus.
And on both sides, lie the lungs.
And as you can see in the figure, esophagus crosses the diaphragm to enter into the abdomen, where it joins the stomach.
Esophagus starts at a distance of 15 cm from upper incisors, at the level of cricopharyngeus muscle.
And the lowest most end of the esophagus is at distance of 40 cm from upper incisors, at the level of gastroesophageal junction.
So the total length of the esophagus is 25 cm. The upper 3 cm of esophagus is called as cervical esophagus.
And below that esophagus maybe divided into 3 parts – upper, middle and lower esophagus, as you can see in the figure.
Carcinoma rising from the upper and middle esophagus is mostly squamous cell carcinoma. Adenocarcinoma is seen very rarely in this region.
Whereas, in the lower 1/3d of the esophagus, it is mostly adenocarcinoma, although squamous cell carcinoma may also be seen.
So after knowing the anatomy of esophagus, now let’s discuss the staging for esophageal cancer.
TNM Staging Of Esophageal Cancer explained with Video and Images
The staging system used for esophageal cancer is known as TNM staging system.
This diagram is a magnified image of a cross-section of the wall of esophageal. Imagine the upper part is the inner side and the lower part is the outer side. The innermost layer is called as epithelium, followed by this layer, called as lamina propria.
Outer to the lamina propria is this layer called muscularis mucosa.
Outer to which, lies this layer which is called as submucosa. Then lies muscularis propria.
And on the outermost aspect, lies this layer which is called as serosa or adventitia.
Now, let’s discuss the T-staging for esophageal cancer.
First is Tis, or carcinoma in situ. This is not considered malignant and is localized to the epithelium.
Infiltration of lamina propria or muscularis mucosa is called as T1a disease.
Infiltration into submucosa is called as T1b.
Muscularis propria infiltration is called as T2. And infiltration of serosa or adventitia is called as T3.
Till T3 disease, the cancer is limited to the wall of esophageal and does not extend outside to involve adjacent structures.
Whereas in T4 disease, cancer infiltrates through the wall of esophageal and involves adjacent structures, like in this figure, cancer has infiltrated into the heart or pericardium.
And here, it has infiltrated into the lungs or pleura.
And here it infiltrates the diaphragm.
It may also infiltrate anteriorly, into the trachea. Or into the great vessels of the heart.
So this finishes the T-stage, now let’s come to the N-stage.
N staging maybe N1, N2 or N3, depending upon the number of lymph nodes involved.
Last comes the M or the metastatic staging, which determines the spread of cancer to distant sites. Like in this figure, cancer has spread to involve both the lungs.
And here it has spread to the liver in form of multiple nodular deposits.
Rarely, cancer may spread to bones.
So this completes the TNM staging for esophageal cancer.
Esophagus Cancer TNM Staging
Esophageal cancer TNM staging helps to determine the disease prognosis and to select an appropriate treatment strategy. It is the most commonly used staging system for esophageal cancer.
“T” stands for “Tumor Size”, “N” for “Lymph Nodes”, and “M” for “Metastasis”. Numbers and/or letters after T (is, 1a, 1b, 2, and 3), N (0, 1, 2, and 3), and M (0 and 1) provide more details about each of these factors.
|Tis||Pre-cancerous or cancerous cells present only in the epithelium of esophagus|
|T1a||Tumor invades mucosa|
|T1b||Cancerous cells present in all layers of the esophagus epithelium and into the middle muscular layer|
|T2||Tumor invades the muscular layer (muscularis propria)|
|T3||Tumor invades in the serosa/adventitia|
|T4a||Tumor invades the pleura, pericardium, azygous vein, diaphragm , or peritoneum|
|T4b||Tumor invades other adjacent structures, such as aorta, vertebral body, or airway.|
|N0||No regional lymph node involvement|
|N1||Tumor has spread to 1 to 2 regional lymph nodes|
|N2||Tumor has spread to 3 to 6 regional lymph nodes|
|N3||Tumor has spread to 7 or more regional lymph nodes|
|M0||No spread to distant sites|
|M1||Spread to distant sites like lungs, pleura, peritoneum, liver, bones, etc|
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