Overview of tonsil cancer

Tonsil cancer is a type of cancer in which an abnormal growth of cells begins in the tonsils, which may spread to other parts of the body. The tonsils, found at the back of the mouth, are part of the immune system. Along with the tongue and soft palate, this area of the mouth is known as the oropharynx. 

Among oropharyngeal cancers, tonsil cancer is the most common, accounting for 23.1% of cases.¹ Common risk factors for tonsil cancer include smoking and drinking alcohol, while common symptoms include having a sore throat and difficulty swallowing (dysphagia).² In recent decades, oropharyngeal cancers -especially tonsil cancer- have been increasingly associated with human papillomavirus 16 (HPV 16), a common sexually transmitted disease. Of note, those with HPV 16-positive tonsil cancer seem to have a better prognosis than those who have HPV 16-negative tonsil cancer.³

How is tonsil cancer staged?

To determine the extent of tonsil cancer, healthcare providers use various diagnostic systems to guide treatment decisions. This article focuses on clinical staging, which applies to patients who do not undergo surgery or biopsy. Clinical staging is based on physical examination, patient history, and imaging studies such as CT or MRI.

The TNM system

Almost all types of cancers can be described using the TNM system. TNM is an acronym for Tumour, Node and Metastasis and is used to accurately describe the size and spread of a tumour. In the context of tonsil cancer, the TNM system can be thought of in this way: 

• Tumour (T): Describes the size of the primary tumour/mass of cells and whether it has spread to other areas close to the tonsils, such as the voice box (larynx) or the epiglottis
• Node (N): Refers to whether the tumour has spread to nearby lymph nodes. Lymph nodes, as well as tonsils, form part of the lymphatic system, which is a key part of our immune system. The lymph nodes located closest to the tonsils are found in the neck, and doctors may check if an individual's lymph nodes are swollen here if they suspect tonsil cancer
• Metastasis (M): Indicates if the primary tumour cells have broken off and spread to other distant areas in the body. In tonsil cancer, metastasis would be classified if the cancer has spread beyond the oropharynx, e.g. if cancer cells were found in the lungs

This system can be further be sub-categorised to better describe how the cancer has progressed.

Tumour (T)

• T1 - Tumour is 2 cm or smaller
• T2 - Tumour is between 2 and 4 cm in size
• T3 - Tumour is greater than 4 cm or the tumour has spread to nearby surface tissues and structures, such as the top of the voice box (larynx)
• T4 - Tumour is larger than 4 cm and has spread deeper to the tongue, soft palate and invaded tissues such as muscle and bone of the jaw

Node (N)

• N0 - Nearby lymph nodes do not contain any cancer cells
• N1 - At least one lymph node contains cancer cells. This lymph node is found on the same side as the affected. The combined area of the cancer cells on the lymph node is less than 3 cm
• N2 - Cancer in both lymph nodes of the neck, or the size of at least one tumour on the lymph node is between 3-6 cm
• N3 - At least one lymph node is found to be larger than 6 cm, indicating swelling has occurred

Metastasis (M)

• M0 - Tumour has not spread far from the tonsils. No metastasis has occurred.
• M1 - Cancer cells have broken off from the primary tumour on the tonsils and spread beyond the oropharynx, e.g. the lungs.

During check-ups, monitoring changes in TNM classification can help doctors guide treatments used to manage tonsil cancer.

The numerical staging system

A numerical staging system can also be used with the TNM system to better report on how the cancer cells have changed in shape, size and movement. In the context of tonsil cancer, these stages can be described as follows. 

• Stage 1 - Tumour is small in size and confined within the tonsils
• Stage 2 - Larger tumour, but is only found within the tonsils
• Stage 3 - Cancer has spread from the tonsils to nearby tissues of the oropharynx, including lymph nodes in the neck
• Stage 4 - Cancer has spread to multiple lymph nodes on the neck or the cancer has spread from the tonsils to other organs. of the body. This is also known as metastatic cancer or secondary cancer as the cancer cells originated from a primary mass in the tonsils

Clinical implications of cancer staging

The TNM system can be used to stage tonsil cancer. As the criteria for these often overlap, this can be simplified as follows.⁴

• Stage 1 -T1-T2, N0, M0
• Stage 2 -T1-T2, N1, M0
• Stage 3 - T3-T4, N2-N3, M0
• Stage 4 - T1-T4, N1-N3, M1

Using this simplified staging system, doctors and healthcare professionals can better plan appropriate management and treatment plans for patients. 

If the tumour mass is small and contained within the tonsils (stage 1), surgery can be performed to remove the tumour from the body to prevent it from spreading and potentially metastatizing. For a larger tumour that is spreading beyond the tonsils (stage 2), the addition of radiotherapy in a patient's treatment plan may be added to help shrink the size of the tumour.

With more advanced tonsil cancer, a combination of radiotherapy and chemotherapy may be used if the tumour is deemed unsuitable to be removed by surgery. This treatment method avoids excessive surgical procedures, which carry risks in themselves. This is a common treatment used in advanced cancers across the whole body. For stage 4 tonsil cancer, as with other metastatic diseases, treatments are focused on slowing the growth of the cancer, and additional targeted therapies can be used (e.g. immunotherapies) to target and attack cancer cells specifically.

Summary

Tonsil cancer is one of the most common types of oropharyngeal cancers. Common risk factors for tonsil cancer include smoking and drinking alcohol. However in recent history, the association of tonsil cancer with HPV 16 has greatly influenced survival estimations. Different diagnostic criteria can be used to assess how advanced tonsil cancer is. From these observations, tonsil cancer can be classified into 4 stages, with stage 1 being early cancer and stage 4 being the most advanced. These stages are very important in diagnosis as they allow doctors and healthcare professionals to implement the most appropriate treatment strategy for a patient to best increase their chance of survival.