Types Of Oral Cancer

Overview 

Oral cancer (OC) refers to cancers in the mouth and back of the throat. Tumours can also develop in the area of the throat (pharynx) and back of the mouth, referred to as oropharyngeal cancer. 

Although considered a rare form, anyone is susceptible to developing OC. The risk increases with age, where most diagnosed cases are between the ages of 66 and 70. 

Understanding the differences in types of OC is crucial for accurate diagnosing and treatment to improve prognosis. Patient education is vital as this type of cancer can spread quickly, reinforcing the importance of early detection. 

This article explains the various types of OC, how they can be identified, and their risk factors. Read on to find out the treatment options available and what you can do to prevent the risk of developing OC.

What is oral cancer? 

OC includes malignant growth that commonly starts in the squamous cells, which are thin, flat cells that line the inside of your mouth and lips. The majority tend to be diagnosed as oral squamous cell carcinomas (OSCC).¹

The following stages of OC include:

• Stage 0 (carcinoma in situ) - Presence of cancer cells contained in the lining of the mouth
• Stage 1 - Cancer is less than 2 cm across and 5 mm deep. It has not spread to nearby tissues
• Stage 2 - Cancer is either less than 2 cm or 2-4 cm across and 5-10 mm in depth. It has not spread to nearby lymph nodes and organs
• Stage 3 - Cancer is either 2-4 cm across and deeper than 10 mm, or larger than 4 cm across but no deeper than 10 mm and has not spread, or the cancer is any size where one lymph node on the same side contains cancer cells and does not exceed 3 cm
• Stage 4 - Cancer has spread outside the mouth into surrounding structures such as tissues, lymph nodes, or other parts of the body including the lungs and bones

The cause of mutations in squamous cells resulting in cancer is not clear. However, the following factors can increase your risk of developing OC:²

• Tobacco use, including smoking and use of smokeless tobacco
• Alcohol intake
• Excessive sun exposure
• Human papillomavirus virus (HPV)
• Poor oral hygiene
• A weakened immune system

Types of oral cancer 

Oral squamous cell carcinoma (OSCC)

OSCC is a commonly known malignancy accounting for over 90% of total OC and is strongly related to alcohol and tobacco use.³

It is characterised by lesions with a slightly uneven surface and distinct borders which do not heal. The lesions are classified into two types; leukoplakia which are white patches, and erythroplakia which are red, velvety patches. Erythroplakia are known to be more commonly associated with carcinoma as they have higher malignant potential than leukoplakia.⁴

OSCC can appear in any location in the mouth, however, 50% of cases are found in the tongue and other following sites:^3,5

• Mouth floor
• Soft palate
• The gingiva (gums)
• Buccal mucosa
• Hard palate

OSCC can metastasize to lymph nodes of the neck and distant organs including the lungs, liver and bones.³

Common symptoms include:

• Lumps on the lip or mouth that do not heal
• White and red patches on the gums, tongue, tonsils, or lining of the mouth
• Difficulty chewing and swallowing
• Impaired speech
• Change in taste
• Mouth and jaw pain
• Numbness in the tongue or mouth
• Sore throat

As the cancer progresses, a lump, ulcer or growth can form. Ulcer formation is common with OSCC and is typically hard to the touch as the elasticity of the soft tissue changes.⁵ 

Early carcinomas often go unnoticed due to their asymptomatic features as pain generally arises when the lesions have reached a remarkable size, and by then medical attention is necessary for the patient.⁵

Verrucous squamous cell carcinoma (VSCC) 

VSCC is a rare subtype of squamous cell carcinoma making up about 5% of all OC, prevalent in the buccal mucosa, gingiva and tongue. It typically does not metastasize to other parts of the body but can invade nearby tissues.

The appearance includes a white or grey, outward growing, broad-based lesion with a cauliflower-like warty surface. This is unlike SCC, where invasion occurs in underlying tissues.⁶

VSCC is characterised by having slow growth, which means it could take several years to reach a size that exhibits symptoms, including the following:⁶ 

• Discomfort
• Difficulty chewing and swallowing
• Bad breath
• Pain, signifying tumour invasion into adjacent tissues 

VSCC is also strongly associated with alcohol and tobacco use and is less aggressive and invasive than SCC with a better prognosis if treated early. 

Minor salivary gland carcinomas

OC can develop on the minor salivary glands which are found on the upper aerodigestive tract and has shown no association with alcohol and tobacco use. 50% of tumours found in this region are malignant and sometimes located in the palate.⁷ They include mucoepidermoid carcinoma (MEC) and polymorphous low-grade adenocarcinoma (PLGA). 

Mucoepidermoid carcinoma (MEC)

MECs are the most common minor salivary gland cancers associated with radiation exposure. They are characterised by mucous cells, squamous epithelial cells and intermediate cells.

They often develop with no symptoms and are a firm mass with swelling, pressure, occasional pain and sometimes facial paralysis. It most commonly affects the parotid gland but can occur in the palate, lips and tongue. High-grade tumours can metastasize to local lymph nodes but are rare in distant sites.⁸

Polymorphous low-grade adenocarcinoma (PLGA)

PLGA appears as a painless and well-circumscribed mass, mostly found on the palate due to the high concentration of minor salivary glands. The lesion is a slow-growing mass that can reach sizes of 1-4 cm. It can also be accompanied by ulcers, bleeding and differences in the texture of the mucosal lining as the lesion infiltrates bony tissue. It generally has a good prognosis if treated early, with a low recurrence rate.⁷

Lymphomas 

The lymphatic system includes the lymph nodes, bone marrow, spleen and thymus gland. The base of the tongue and tonsils contain lymphatic tissue and lymphomas develop when lymphocytes multiply out of control. The two main types of lymphomas are Hodgkin’s lymphoma and non-Hodgkin’s lymphoma.⁹

Lymphomas are rare and sometimes difficult to diagnose because they display similar symptoms to other diseases such as periodontitis, including tooth mobility and tooth pain. Additional symptoms can involve:

• Painless swelling with or without ulcers in the tonsils, palate, buccal mucosa and tongue
• Enlarged lymph nodes in the neck
• Difficulty swallowing
• Persistent sore throat 

Other rare types

Several other rare types include:

• Sarcomas -  Soft tissue sarcomas can develop in the oral cavity and tongue as an asymptomatic mass with discomfort
• Melanomas -  Melanomas originate from cancer of melanin-producing melanocytes. They can occur as a black-brown patch with several shades of grey, red and purple areas of depigmentation in the oral cavity¹⁰
• Adenoid cystic carcinoma (ACC) - ACC arises in the salivary glands as painless and slow-growing masses. As the tumour advances, pain, changes in speech and nerve paralysis may be felt

Diagnosis 

Early detection is important as OC can spread quickly. Methods of diagnosis can include:¹¹

• Clinical inspection of the oral cavity to identify abnormalities such as lesions, ulcers, lumps and discoloration
• Imaging, including computed tomography (CT) scans, magnetic resonance imaging (MRI), X-rays, and ultrasounds
• Biopsy, which includes removing a small sample of the affected area to be sent to a pathologist for cancer testing

Treatment

Treatment options depend on the location, type, stage and health of the patient, and usually involve combinations of the following:

• Surgery - This is common, particularly for early-stage OC. The cancerous cells are removed without affecting surrounding healthy tissues and structures, such as nerves and blood vessels.⁴  Surgery may also be performed on the jawbone, tongue, larynx and neck. Some patients may require reconstructive surgery to aid breathing and eating
• Radiotherapy -  In advanced stages, beams with intense energy are used to kill cancer cells and shrink tumours by slowing their growth. This type is known as external beam radiotherapy
• Chemotherapy -  Anti-cancer drugs circulate through the bloodstream to destroy and kill cancer cells. Common drugs for OC include cisplatin and fluorouracil and they are typically administered alongside radiotherapy as it can help it to work better
• Targeted and immunotherapy drugs -  Targeted therapy targets different molecules or pathways resulting in the growth of cancer cells. An example is the drug cetuximab. Immunotherapies include drugs that help the immune system attack cancer, such as nivolumab

Prognosis

Survival rates are better in those with early stages of OC compared to those in advanced stages. When diagnosed at an early stage, the 5-year survival rate is 86%, in comparison to 69% when the cancer has advanced to surrounding tissues and organs. The survival rate decreases to 40% if cancer has spread to distant parts of the body. OC patients have a higher risk of recurrence in local areas and developing new primary cancers, thus control of lifestyle is a priority.⁴ 

Prevention

OC cannot be prevented. Although the following strategies can be adopted to reduce the risk of development:

• Early detection. Early diagnosis of OC results in less aggressive treatment, improving the quality of life and 5-year survival rate.¹² Therefore, it is crucial to visit a doctor if you think you display symptoms of any type of OC
• Lifestyle changes. Preventative steps to avoid known risk factors include avoiding smoking, reducing alcohol consumption, limiting sun exposure, wearing protective lip balms, and good oral hygiene
• Regular dental visits to help detect OC at early stages when it is most treatable

Summary 

Oral cancer is commonly diagnosed as oral squamous cell carcinoma. Uncommon types include verrucous squamous cell carcinoma, lymphomas and cancer of the minor salivary glands, such as mucoepidermoid carcinoma and polymorphous low-grade adenocarcinoma. Rare types include sarcomas, melanoma and adenoid cystic carcinoma. Each type consists of different characteristics, symptoms and treatment options, underlying the importance of patient education and early diagnosis for improved prognosis.