Oral cancer classification

Oral cancer can be classified into three types based on the potential to spread to other parts of the body such as malignant tumors,precancerous conditions, and benign tumors. Most common type of malignant tumor of the mouth is squamous cell carcinoma. Squamous cell carcinoma is further classified based on macroscopic and microscopic features. About 5% of oral cavity cancers are rare malignant tumors that start in different types of cells in the oral cavity. These include salivary gland cancer, melanoma, bone and soft tissue sarcomas, Lymphomas and extramedullary plasmacytomas, Hodgkin lymphoma, and non-Hodgkin lymphoma metastatic cancer.

• Malignant tumors of the oral cavity are cancerous growths that have the potential to spread (metastasize) to other parts of the body.
• The oral cavity is lined with squamous epithelium, which is formed by flat, scale-like cells called squamous cells.
• The most common oral cavity cancer starts in these cells and is called squamous cell carcinoma (SCC).

• Squamous cell carcinomas (SCC) make up 95% of all oral cavity cancers. They are classified based on macroscopic or microscopic features.
  • Macroscopic features:
  • Can be seen without a microscope
  • Squamous cell carcinomas are described as following based on macroscopic features:

• Infiltrative – Cancer is growing into deep layers of the oral cavity
• Exophytic – Cancer is growing outwards from the surface of the oral cavity
• Verrucous– Cancer has a wart-like appearance
• Ulcerated– Cancer appears as an open sore
• Flat – Cancer appears as an abnormal area in the lining of the oral cavity

• Microscopic features:
• Squamous cell carcinomas (SCC) are further divided into the following types based on microscopic features:

• Classical or conventional SCC: Most cancers of the oral cavity are classical or conventional squamous cell carcinoma. This type of SCC starts in the squamous epithelium that lines the oral cavity and occurs most often on the lower lip, tongue and floor of the mouth.
• Variants of SCC: These squamous cell carcinomas have distinct microscopic features that make them look and behave differently from classical SCC.

• Verrucous carcinoma
• Basaloid SCC
• Papillary SCC
• Spindle cell carcinoma (SpCC)
• Acantholytic SCC
• Adenosquamous carcinoma
• Lymphoepithelial carcinoma

• About 5% of oral cavity cancers are rare, malignant tumors that start in different types of cells in the oral cavity.
  • Salivary gland cancer
  • Melanoma
  • Bone and soft tissue sarcomas
  • Lymphomas and extramedullary plasmacytomas
  • Hodgkin lymphoma
  • Non-Hodgkin lymphoma
  • Metastatic cancer

• Several types of non-cancerous tumors and tumor-like conditions can arise in the oral cavity and oropharynx.
• A pre-malignant (or precancerous) lesion is defined as a benign, morphologically-altered tissue that has a greater than normal risk of becoming malignant.
• There are several different types of pre-malignant lesions that occur in the mouth.
• Some oral cancers begin as white patches (leukoplakia), red patches (erythroplakia), or mixed red and white patches (erythroleukoplakia or “speckled leukoplakia”).
• The most common pre-cancerous conditions of the oral cavity are:
  • Leukoplakia
  • Erythroplakia
  • Erythroleukoplakia
  • Proliferative verrucous leukoplakia (PVL)
  • Oral submucous fibrosis

• Benign tumors: There are many different types of benign oral cavity tumors.
  • Hyperplasia
  • Papillomas
  • Pleomorphic adenoma
  • Soft tissue tumors
    • Lymphangioma
    • Hemangioma
    • Neurofibroma
    • Lipoma
• Benign odontogenic tumors and cysts
  • Osteoma
  • Ossifying fibroma
• Benign conditions
  • Candidiasis (thrush)
  • Aphthous ulcers (canker sores)
  • Recurrent herpes labialis (cold sores)
  • Erythema migrans (geographic tongue)
  • Hairy tongue
  • Lichen planus
  • Frictional hyperkeratosis
  • Mucocele

The TNM classification of oral cavity carcinoma is as follows:^[1]

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