Learning Center: Access information in greater detail.

Tumors of the Oral Cavity (mouth and lips)

Use the search tool, scroll down for your topic of interest, or use the learning center index at the bottom of this page.

Oral cavity anatomy

Last reviewed: October 4, 2026

Introduction

Oral cavity cancer starts in the mouth: the front two-thirds of the tongue, the floor of the mouth, the gums, the inner cheeks, the hard palate, the area behind the last molars (retromolar trigone) and the lips. About 9 in 10 are squamous cell carcinomas that begin in the surface lining. Tobacco, alcohol and betel quid are the main causes, and, unlike throat (oropharyngeal) cancer, very few oral cavity cancers are caused by HPV [1, 2].

Surgery is the main treatment for most oral cavity cancers, usually with removal of lymph nodes in the neck, and with radiation or chemoradiation afterward when the pathology shows features that raise the risk of recurrence [3, 2]. A randomized trial showed that removing the neck lymph nodes at the first operation, even when they look normal, improves survival in early oral cancer [4]. The sections below cover anatomy, evaluation and staging, the types of tumors, and surgery, reconstruction and recovery. A numbered reference list is at the end of the page.

The mouth consists of two regions: the vestibule and the oral cavity proper. The vestibule is the area between the teeth, lips and cheeks. The oral cavity is bounded at the sides and in front by the alveolar process (containing the teeth) and at the back by the isthmus of the fauces. Its roof is formed by hard palate at the front, and a soft palate at the back. The uvula projects downwards from the middle of the soft palate at its back. The floor is formed by the mylohyoid muscles and is occupied mainly by the tongue. A mucous membrane – the oral mucosa, lines the sides and under surface of the tongue to the gums, lining the inner aspect of the jaw (mandible). It receives the saliva from the submandibular and sublingual salivary glands. From a cancer staging standpoint, mouth and the lips, even the skin covering the lips, is considered part of the oral cavity.

evaluation of oral tumors

Evaluation of a growth or problem in the mouth is typically started with a history and physical examination by a head and neck surgeon, an oral surgeon, a dentist, or another physician. In a head and neck surgeon’s office, the examination involves inspection of all oral surfaces, checking the neck for enlarged lymph nodes, and using a scope to check the back of the tongue and the remainder of the throat. Visual inspection can identify these and also other lesions that are more dangerous looking. A small biopsy of a suspicious are can typically be performed in the clinic and sent for pathological diagnosis. If an enlarged neck lymph node is identified, it too may be biopsied with a needle. Imaging such as CT scan may follow. The pathology report(s) indicate whether the area is cancer and if so, what type of cancer.

Imaging

CT and MRI are the main scans of the mouth and neck. CT is better at showing whether the cancer has worn into the jawbone, while MRI shows soft tissue, nerves and bone marrow in more detail and is less affected by dental fillings; sometimes both are used. PET-CT is used mainly for larger tumors or when lymph nodes are involved, to look for spread to distant sites. A dental evaluation, including a panoramic jaw X-ray, and evaluation by a speech and swallowing therapist and a nutritionist are recommended before treatment, especially if radiation may be needed [3].

Staging and depth of invasion

Oral cancers are staged with the TNM system (tumor, lymph nodes, metastasis). Since 2017 the American Joint Committee on Cancer (AJCC, 8th edition) has included depth of invasion, how far the tumor grows beneath the surface, in the tumor (T) category [5]. The change was based on an international study of 3,149 patients showing that depth predicts survival better than surface size alone [6]. In simplified terms [5, 3]:

T1: 2 cm or smaller and 5 mm deep or less.
T2: 2 cm or smaller and more than 5 mm deep, or 2 to 4 cm and 10 mm deep or less.
T3: larger than 4 cm, or more than 10 mm deep.
T4: growing into nearby structures such as the jawbone, the skin of the face or deeper spaces.

Deeper tumors are more likely to have already spread, unseen, to lymph nodes in the neck, which is why depth also guides decisions about treating the neck (see below and the lymphatics and lymph nodes page).

types of oral cavity tumors

Commonly, a swelling in the mouth is not a tumor at all, instead proving to be an area of irritation, infection, or blocked saliva gland. A benign condition called tori (torus mandibularis on the lower jaw and torus palatini on the roof of the mouth) in which bone slowly gets larger in this area rarely causes a problem. White patches of the surface of the mouth, if not a fungal infection called thrush, are considered pre-cancerous lesions (called leukoplakia), have about a 2% chance of becoming cancer, and usually undergo observation. Red patches of oral lining are more suspicious and can range from erythroplakia (which is not cancerous, but has 15-50% chance of becoming cancer). These are often biopsied to have a definitive diagnosis. Of cancers, the most common type is squamous cell carcinoma, which is often (but not always) associated with tobacco use. Adenocarcinoma, cancer arising from a gland, is the next most common and this category includes mucoepidermoid carcinoma, adenoid cystic carcinoma, acinic cell carcinoma, and polymorphous low grade adenocarcinoma. Melanoma can arise from the surface of the mouth. Sarcoma and lymphoma are also identified, although less commonly, in the mouth. Salivary duct carcinoma and epithelial-myoepithelial carcinoma are much less common types of oral cancer.

What raises the risk

Tobacco and alcohol are the two main causes. Smoking and smokeless tobacco each raise the risk, heavy drinking raises it further, and the two together multiply the effect. Stopping tobacco and limiting alcohol lower the risk over time [1] (see how to quit tobacco).
Betel quid and areca nut chewing, common in South and Southeast Asia, is a leading cause worldwide, even when chewed without tobacco [1].
Sun exposure is a cause of lip cancer, and a weakened immune system also raises the risk.
HPV causes only a small fraction of oral cavity cancers, in contrast to cancers of the tonsils and base of tongue (see the oropharynx page) [1].

Non-healing sores, white or red patches, and lumps in the mouth that last more than two to three weeks deserve examination (see oral lesions).

surgery for oral cancer

Surgery remains the mainstay for treating oral cancer because it is the treatment type that has the highest success rate and the lowest complication rate. Advanced or high risk cancers, when treated for cure, may also undergo radiation or chemotherapy plus radiation. Surgery for cure consists of removing the entire cancer plus a cuff or margin of normal tissue around the cancer. Because of the many functions and complex anatomy of the oral cavity, this means very different things for different cancers. Removal of part or all of the tongue or floor of mouth differs from removing teeth and jawbone, which also differs from removing a portion of the lips or lining of the cheek. Every oral cancer surgery is customized to the cancer. Removal of neck lymph nodes is often included in the operation. Reconstruction is often needed for restoring function, including for eating, talking, and for appearance. Radiation therapy may be recommended shortly after healing from surgery is complete.

Margins

The surgeon aims to remove the tumor with about 1 to 1.5 cm of normal-appearing tissue around it, so that the pathologist finds a clear margin under the microscope. A margin is usually called clear when the cancer is 5 mm or more from the edge, close when it is 1 to 5 mm, and positive when cancer reaches the edge [3]. Close or positive margins raise the risk of the cancer returning and are a reason to consider more surgery or added treatment [7].

Treating the neck lymph nodes

Even when the neck feels and looks normal on scans, about 20% to 30% of early oral cancers have already spread microscopically to neck lymph nodes; in the Japanese trial described below, a quarter to a third of patients had cancer in their nodes [8]. There are two main ways to deal with this risk:

Elective neck dissection removes the at-risk lymph nodes at the same operation (see neck dissection). In a randomized trial of 596 patients with early, node-negative oral cancer at Tata Memorial Centre in India, removing the nodes up front improved three-year overall survival (80.0% compared with 67.5%) and disease-free survival (69.5% compared with 45.9%) compared with watching the neck and operating only if nodes appeared [4]. The NCCN guidelines recommend elective neck dissection for tumors deeper than about 3 mm and consider it for thinner tumors [3].
Sentinel lymph node biopsy finds and removes only the first one to three lymph nodes that drain the tumor (see sentinel node biopsy). If they are free of cancer, a full neck dissection can be avoided. In a Japanese randomized trial of 271 patients with early oral cancer, sentinel node-guided surgery gave three-year survival equal to elective neck dissection (87.9% and 86.6%), with less effect on neck and shoulder function [8]. A French randomized trial of 307 patients with early oral and oropharyngeal cancer found equivalent control of the neck (two-year neck recurrence-free survival about 90% in both groups), a slightly shorter hospital stay, and better neck and shoulder function during the first six months in the sentinel node group [9]. Sentinel node biopsy requires specialized nuclear medicine support and is less reliable for floor-of-mouth tumors, which sit close to the first nodes [3].

Radiation or chemoradiation after surgery

Radiation is usually recommended after surgery for larger tumors, close margins, more than one involved lymph node, or invasion of nerves or small vessels [3]. Two randomized trials, EORTC 22931 and RTOG 9501, tested adding cisplatin chemotherapy to radiation after surgery. Adding chemotherapy improved control of the cancer, and in the EORTC trial it also improved survival [10, 11]. A combined analysis of the two trials found that the patients who clearly benefit are those with cancer extending outside a lymph node (extranodal extension) or a positive margin [7], and this was confirmed at ten-year follow-up [12]. Chemoradiation is harder on the body than radiation alone, so the decision is made case by case (see radiation therapy).

Reconstruction

When removing a cancer leaves a large defect, it is often rebuilt with a free flap: skin, muscle or bone moved from the forearm, thigh or lower leg and reconnected to blood vessels in the neck under a microscope. A systematic review found that free flaps give better long-term speech, swallowing and quality of life than local flaps for larger defects [13]. In a national Taiwanese cohort of 8,646 patients, those reconstructed with free flaps more often had clear margins and had better survival than those reconstructed with local flaps, likely because larger, safer resections were possible [14]. The two most common soft-tissue flaps, from the forearm (radial forearm) and the thigh (anterolateral thigh), have similar success and function [15]. When part of the jaw must be removed, it is usually rebuilt with bone from the lower leg (fibula free flap).

Swallowing and speech

Swallowing and speech depend mostly on how much of the tongue and floor of mouth is removed and whether radiation is added. Function is usually at its worst in the first weeks to months and improves over the following year. Speech and swallowing therapists work with patients before and after surgery, and exercises, dental prostheses and, when needed, a temporary feeding tube help maintain nutrition [3] (see swallowing and feeding tube placement).

Survival

Survival depends mainly on stage. In a national SEER analysis of oral cancer from 1973 to 2014, survival improved over time, and three-year survival for early-stage disease reached about 90% in the most recent period, while advanced-stage disease remained lower [16]. Spread to the neck lymph nodes, particularly with extranodal extension, is one of the strongest predictors of outcome [2]. These figures describe large groups and cannot predict an individual result.

Additional links

• Link to American Head and Neck Society site with short answers to frequently asked questions about cancer of the mouth.

• Link to the American Cancer Society website with information on oral cavity and oropharynx cancers.

Summary

Most oral cavity cancers are squamous cell carcinomas caused by tobacco, alcohol or betel quid; few are HPV-related [1].
Evaluation includes a biopsy, CT and/or MRI, PET-CT for advanced disease, and a dental evaluation before treatment [3].
Depth of invasion is part of staging and predicts the risk of hidden lymph node spread [5, 6].
Surgery with clear margins is the main treatment. Treating the neck at the first operation improves survival in early cancer, and sentinel node biopsy is an alternative in selected patients [4, 8].
Radiation, or chemoradiation for extranodal extension or positive margins, is added after surgery for higher-risk cancers [7].
Free flap reconstruction and speech and swallowing therapy help restore function [13].

References

Bouvard V, Nethan ST, Singh D, et al. IARC Perspective on Oral Cancer Prevention. N Engl J Med. 2022;387(21):1999-2005. doi:10.1056/NEJMsr2210097 PubMed 36378601
Chow LQM. Head and Neck Cancer. N Engl J Med. 2020;382(1):60-72. doi:10.1056/NEJMra1715715 PubMed 31893516
National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Head and Neck Cancers. Version 2.2026. nccn.org
D'Cruz AK, Vaish R, Kapre N, et al. Elective versus Therapeutic Neck Dissection in Node-Negative Oral Cancer. N Engl J Med. 2015;373(6):521-9. doi:10.1056/NEJMoa1506007 PubMed 26027881
Lydiatt WM, Patel SG, O'Sullivan B, et al. Head and Neck cancers-major changes in the American Joint Committee on cancer eighth edition cancer staging manual. CA Cancer J Clin. 2017;67(2):122-137. doi:10.3322/caac.21389 PubMed 28128848
Ebrahimi A, Gil Z, Amit M, et al. Primary tumor staging for oral cancer and a proposed modification incorporating depth of invasion: an international multicenter retrospective study. JAMA Otolaryngol Head Neck Surg. 2014;140(12):1138-48. doi:10.1001/jamaoto.2014.1548 PubMed 25075712
Bernier J, Cooper JS, Pajak TF, et al. Defining risk levels in locally advanced head and neck cancers: a comparative analysis of concurrent postoperative radiation plus chemotherapy trials of the EORTC (#22931) and RTOG (# 9501). Head Neck. 2005;27(10):843-50. doi:10.1002/hed.20279 PubMed 16161069
Hasegawa Y, Tsukahara K, Yoshimoto S, et al. Neck Dissections Based on Sentinel Lymph Node Navigation Versus Elective Neck Dissections in Early Oral Cancers: A Randomized, Multicenter, and Noninferiority Trial. J Clin Oncol. 2021;39(18):2025-2036. doi:10.1200/JCO.20.03637 PubMed 33877855
Garrel R, Poissonnet G, Moyà Plana A, et al. Equivalence Randomized Trial to Compare Treatment on the Basis of Sentinel Node Biopsy Versus Neck Node Dissection in Operable T1-T2N0 Oral and Oropharyngeal Cancer. J Clin Oncol. 2020;38(34):4010-4018. doi:10.1200/JCO.20.01661 PubMed 33052754
Bernier J, Domenge C, Ozsahin M, et al. Postoperative irradiation with or without concomitant chemotherapy for locally advanced head and neck cancer. N Engl J Med. 2004;350(19):1945-52. doi:10.1056/NEJMoa032641 PubMed 15128894
Cooper JS, Pajak TF, Forastiere AA, et al. Postoperative concurrent radiotherapy and chemotherapy for high-risk squamous-cell carcinoma of the head and neck. N Engl J Med. 2004;350(19):1937-44. doi:10.1056/NEJMoa032646 PubMed 15128893
Cooper JS, Zhang Q, Pajak TF, et al. Long-term follow-up of the RTOG 9501/intergroup phase III trial: postoperative concurrent radiation therapy and chemotherapy in high-risk squamous cell carcinoma of the head and neck. Int J Radiat Oncol Biol Phys. 2012;84(5):1198-205. doi:10.1016/j.ijrobp.2012.05.008 PubMed 22749632
Galviz Tabares B, Ruiz Geithner CM, Pierpoline J, et al. Long-Term Functional Outcomes of Free Flaps Versus Locoregional Flaps in Soft Tissue Reconstruction for Oral Cavity Cancer: A Systematic Review. J Craniofac Surg. 2025;36(4):1278-1285. doi:10.1097/SCS.0000000000011158 PubMed 40067267
Liao CT, Wen YW, Lee SR, et al. Clinical Outcomes of Taiwanese Patients with Resected Oral Cavity Squamous Cell Carcinoma Who Underwent Reconstruction with Free Versus Local Flaps. Ann Surg Oncol. 2022;29(2):1130-1140. doi:10.1245/s10434-021-10524-x PubMed 34668119
Ranganath K, Jalisi SM, Naples JG, et al. Comparing outcomes of radial forearm free flaps and anterolateral thigh free flaps in oral cavity reconstruction: A systematic review and meta-analysis. Oral Oncol. 2022;135:106214. doi:10.1016/j.oraloncology.2022.106214 PubMed 36302325
Cheraghlou S, Schettino A, Zogg CK, et al. Changing prognosis of oral cancer: An analysis of survival and treatment between 1973 and 2014. Laryngoscope. 2018;128(12):2762-2769. doi:10.1002/lary.27315 PubMed 30194691

Learning Center Main Index: