Squamous Cell Carcinoma of the Oral Cavity: Understanding Your Pathology Report

Section Editor: Jason Wasserman MD PhD FRCPC
July 24, 2026

Squamous cell carcinoma is the most common type of cancer that starts in the oral cavity, the medical name for the mouth. It begins in squamous cells, the thin, flat cells that form the inner lining of the mouth. It can develop anywhere in the oral cavity, including the front two-thirds of the tongue, the floor of the mouth, the inner cheeks, the gums, the hard palate (the bony roof of the mouth), and the moist inner surface of the lips. Cancers that start on the dry, outer surface of the lip are classified as skin cancers of the lip rather than oral cavity cancers, so if your report describes a lip tumor, it is worth asking your doctor which type you have.

This article explains the findings you are likely to see on a pathology report for squamous cell carcinoma of the oral cavity, what each one means, and why it matters for your care.

What causes squamous cell carcinoma of the oral cavity?

Squamous cell carcinoma of the oral cavity develops when the squamous cells lining the mouth are damaged repeatedly over many years. Each time the cells are damaged and repaired, a small number of errors build up in their genetic material. Over time, enough errors accumulate that the cells begin to grow in an uncontrolled way and turn into cancer. Most of this damage comes from things that irritate the lining of the mouth over a long period.

The most common risk factors are:

Tobacco. Every form raises risk, including cigarettes, cigars, pipes, and smokeless products such as chewing tobacco and snuff. Tobacco contains chemicals that damage the cells lining the mouth.
Alcohol. Heavy alcohol use raises risk on its own, and it makes the lining of the mouth more able to absorb the harmful chemicals in tobacco. Using tobacco and alcohol together raises risk much more than either one alone.
Betel quid and areca nut. Chewing betel quid or areca nut, common in parts of South and Southeast Asia and the Pacific, damages the lining of the mouth and is a major cause of oral cancer worldwide.
Previous precancerous changes. Conditions such as oral epithelial dysplasia, a white patch (leukoplakia), or a red patch (erythroplakia) can develop into cancer over time.
A weakened immune system. This includes long-term immune suppression after an organ transplant.

Unlike cancers of the oropharynx (the area at the back of the mouth that includes the tonsils and the base of the tongue), squamous cell carcinoma of the oral cavity is usually not caused by human papillomavirus (HPV). For this reason, HPV testing is not routinely performed on these tumors, and you should not expect to see an HPV result on your report.

One more idea helps explain why long-term follow-up matters. When the whole lining of the mouth has been exposed to tobacco, alcohol, or betel quid for years, the entire surface carries damage, not just the spot where the tumor grew. This is sometimes called field change. It is the reason a second, separate cancer can develop elsewhere in the mouth or throat later on, even after the first tumor has been removed successfully.

What are the symptoms of squamous cell carcinoma of the oral cavity?

Early squamous cell carcinoma of the oral cavity may cause no symptoms and is sometimes found during a routine dental exam. As the tumor grows, most people notice a change in the mouth that does not heal. Common symptoms include:

A sore or ulcer in the mouth that does not heal within two to three weeks
A red patch, a white patch, or a mixed red and white patch that will not rub off
A lump, thickening, or rough area in the mouth
Pain, bleeding, or numbness in one area of the mouth
Loose teeth with no dental cause, or dentures that stop fitting
Difficulty chewing, swallowing, speaking, or moving the tongue or jaw
Ongoing ear pain on one side with a normal ear exam
A lump in the neck, which may mean the cancer has spread to a lymph node

Because these changes can look like ordinary mouth irritation, any sore, patch, or lump that lasts longer than two to three weeks should be examined by a dentist or doctor.

How is the diagnosis made?

The diagnosis of squamous cell carcinoma of the oral cavity is made when a pathologist examines a sample of the tumor under the microscope. The sample is obtained by biopsy, usually a small piece taken from the edge of the abnormal area. Looking at the tumor in the mouth or on an imaging scan is not enough to make this diagnosis.

Under the microscope, the pathologist looks for squamous cells that have broken through the epithelium, the surface lining of the mouth, and grown into the tissue underneath. This downward growth is called invasion, and it is what separates an invasive cancer from a precancerous change such as dysplasia, where the abnormal cells stay on the surface. In most cases, the diagnosis is clear from the appearance of the cells. Occasionally, when a tumor is difficult to identify, the pathologist uses a test called immunohistochemistry to confirm the tumor type.

The first biopsy confirms the diagnosis, but it samples only part of the tumor. Details such as how deeply the tumor has grown, whether it reaches the surgical edges, and whether it involves bone can only be measured accurately after the whole tumor is removed. For this reason, the report on the surgically removed tumor (the resection) contains much more information than the biopsy report. Once cancer is confirmed, imaging such as a CT scan or MRI is used to see how far it extends and whether it has reached the lymph nodes in the neck.

Types of squamous cell carcinoma of the oral cavity

Most squamous cell carcinomas of the oral cavity are described simply as conventional or keratinizing squamous cell carcinoma, and no special type is named. Some reports name a less common type, based on how the tumor looks under the microscope. If your report names one of these, it means the pathologist saw a particular growth pattern. The types you are most likely to see named are:

Verrucous carcinoma. A slow-growing type with a thick, warty surface that rarely spreads to lymph nodes and is usually treated with surgery alone.
Basaloid squamous cell carcinoma. A type that tends to grow quickly and is more often found at an advanced stage.
Spindle cell (sarcomatoid) squamous cell carcinoma. A type in which the tumor cells become long and thin. Immunohistochemistry is often used to confirm the diagnosis.

Histologic grade

The grade describes how much the cancer cells still look like normal squamous cells. The pathologist assigns it by looking at the tumor under the microscope, and it appears on almost every report. Your report will use one of these terms:

Well differentiated (low grade). The cells look very similar to normal squamous cells. These tumors tend to grow more slowly.
Moderately differentiated. The cells look more abnormal. This is the grade reported most often.
Poorly differentiated (high grade). The cells look very different from normal squamous cells and tend to grow more quickly.

Grade is one of the findings your treatment team considers, but on its own it is a weaker predictor than the stage of the cancer, how deeply it has grown, and whether it has reached the lymph nodes. A well differentiated tumor that has grown deeply is a more serious finding than a poorly differentiated tumor that is small and shallow, so grade is best read together with the rest of the report.

Depth of invasion

Depth of invasion measures how far the tumor has grown beneath the surface of the mouth, in millimeters. The pathologist measures from the level of the normal surface lining down to the deepest tumor cell. It is one of the most useful measurements on the report, because tumors that grow more deeply are more likely to have spread to the lymph nodes in the neck. Depth of invasion is combined with the size of the tumor to help determine the stage, described later in this article.

Tumor size

Tumor size is the greatest dimension of the tumor, measured by the pathologist after it has been removed. It is combined with the depth of invasion to determine the tumor stage. The size on the pathology report may be slightly smaller than the size measured on imaging or during surgery, because tissue shrinks after it is removed. This is expected, and your treatment team takes it into account.

Tumor extension into nearby structures

The oral cavity is surrounded by bone, muscle, and other structures, so your report will describe whether the tumor has grown beyond the lining of the mouth into anything nearby. Growth into the jawbone (the mandible or maxilla), into the skin of the face, or into the maxillary sinus (the air space in the cheekbone) raises the stage of the cancer and usually means a larger operation. Growth into these structures is described in the staging section below.

Perineural invasion

Perineural invasion means that cancer cells are growing along or around a nerve. Nerves run throughout the mouth, and they provide a path that cancer cells can follow, sometimes reaching beyond the visible edge of the tumor. Your report will say whether perineural invasion is present or absent. When present, it is linked to a higher chance of the cancer returning at the original site, and it is one of the findings the treatment team considers when deciding whether radiation is needed after surgery.

Lymphovascular invasion

Lymphovascular invasion means that cancer cells have entered a small blood vessel or lymphatic channel near the tumor. These vessels can carry cancer cells away from where the cancer started. Your report will say whether lymphovascular invasion is present or absent. When present, it points to a higher chance that cancer cells have reached the lymph nodes, and it is one of the findings weighed when deciding whether more treatment is needed after surgery.

Surgical margins

Margins are the cut edges of the tissue removed during surgery. The goal of surgery is to remove the tumor along with a rim of normal tissue around it, so that no cancer is left behind. The pathologist coats the edges of the removed tissue with ink and measures how close the tumor comes to each edge.

Negative (clear) margin. No cancer cells at the inked edge, with normal tissue separating the tumor from the edge. This suggests the tumor was removed completely.
Close margin. Cancer cells come near the edge without reaching it. A close margin raises the chance of the cancer returning at the same site.
Positive (involved) margin. Cancer reaches the inked edge, meaning some cancer may remain. This is one of the strongest reasons for further treatment, such as more surgery or radiation.

During surgery, the surgeon may send small pieces of tissue to be examined right away, called frozen sections, so that more tissue can be removed if needed. These results are preliminary. The final margin result in your report is based on the complete removed tissue and is occasionally different from what was reported during surgery.

Lymph nodes

Lymph nodes are small immune organs found throughout the body. Squamous cell carcinoma of the oral cavity usually spreads first to the lymph nodes in the neck, so the surgeon often removes a group of these nodes at the same time as the tumor, in an operation called a neck dissection. The pathologist examines each node and reports:

How many lymph nodes were examined and how many contained cancer. Usually written as a ratio, such as 2 of 34.
Extranodal extension. This means cancer cells have broken through the outer wall of a lymph node into the surrounding tissue. It is an important finding that often leads the treatment team to add chemotherapy to radiation after surgery.

If no cancer is found in any lymph node, your report will say so. This is a favorable finding.

Biomarker and molecular testing

Biomarkers are features of a cancer, such as a protein on the surface of the tumor cells, that help predict how the cancer may respond to a particular treatment. This testing is not needed to make the diagnosis and is not performed on every tumor. It becomes relevant mainly when drug treatment is being considered, such as for cancers that are advanced, have come back, or have spread. If your report does not mention these tests, it usually means they were not needed for your situation.

The biomarker most often tested in squamous cell carcinoma of the oral cavity is PD-L1. PD-L1 is a protein that some tumors use to avoid being attacked by the immune system. A group of drugs called immunotherapy can release this brake so the immune system can attack the cancer. PD-L1 is measured on a sample of the tumor and reported as a number called the Combined Positive Score, or CPS, which can range from 0 to 100. The score reflects how many cells in and around the tumor show PD-L1. A CPS of less than 1 is considered negative. A CPS of 1 or higher is considered positive and means immunotherapy may be an option, and a higher score suggests the cancer is more likely to respond. Your report will give the specific number, and the result helps the treatment team decide whether immunotherapy is a good option. You can read more in the article on PD-L1 testing in cancer.

Depending on your situation, other tests may sometimes be performed, including mismatch repair (MMR) or microsatellite instability (MSI) testing and tumor mutational burden (TMB). Like PD-L1, these can help identify people who may benefit from immunotherapy. If any of these were done, they will be listed on your report or in a separate molecular report. More information is available in the Biomarkers and Molecular Testing section.

Pathologic stage (pTNM)

The pathologic stage describes how far the cancer has spread, based on the tissue examined under the microscope. It uses the TNM system, which has three parts: T for the size and extent of the primary tumor, N for spread to the lymph nodes in the neck, and M for spread (metastasis) to more distant parts of the body. The letter “p” in front, as in pT and pN, means the stage was determined by examining tissue rather than by imaging alone. For oral cavity cancer, the T category combines tumor size with invasion depth, so a small tumor that has grown deeply can fall into a higher category than its size alone would suggest.

Tumor stage (pT)

pTis. Carcinoma in situ. Abnormal cells are confined to the surface lining and have not invaded.
pT1. Tumor 2 cm or smaller, with a depth of invasion of 5 mm or less.
pT2. Tumor 2 cm or smaller with deeper invasion, or larger than 2 cm but not more than 4 cm with limited invasion.
pT3. Tumor larger than 4 cm, or a tumor with deep invasion greater than 10 mm.
pT4a. Tumor has grown into nearby structures such as the jawbone, the maxillary sinus, or the skin of the face.
pT4b. Tumor has grown into deeper structures and usually cannot be removed completely by surgery.

Nodal stage (pN)

pN0. No cancer found in any lymph node.
pN1. Cancer in a single lymph node on the same side as the tumor, 3 cm or smaller, without extranodal extension.
pN2. Cancer in a larger node, in more than one node, or in nodes on both sides of the neck, in ways set out by the staging system.
pN3. Cancer in a node larger than 6 cm, or a node with extranodal extension.

Your report may not include the M category, because spread to distant parts of the body is usually determined by imaging rather than by the pathologist. Your treatment team combines the pathology findings with your scans to arrive at the overall stage. You can read more in the article on TNM staging.

What is the prognosis for squamous cell carcinoma of the oral cavity?

Prognosis means the likely course and outcome of a disease. For squamous cell carcinoma of the oral cavity, prognosis depends most on the stage of the cancer, and in particular on how deeply the tumor has grown, whether the margins are clear, how many lymph nodes contain cancer, and whether extranodal extension is present. Tumors found early, while small and without lymph node spread, are often cured with surgery. Once cancer has reached the lymph nodes, the chance of cure is lower.

The findings on your report that are linked to a higher chance of the cancer returning include a positive or close margin, extranodal extension, cancer in more than one lymph node, deep invasion, and perineural or lymphovascular invasion. These are averages drawn from large groups of patients. They describe general patterns and cannot predict what will happen for any one person.

Two longer-term points are worth knowing. First, because of field change, there is an ongoing risk of a second, separate cancer developing elsewhere in the mouth or throat, and this risk is reduced by stopping tobacco and limiting alcohol. Second, recovery of speech, swallowing, chewing, and dental health is an important part of the outcome and often involves speech therapists, dietitians, and dental specialists.

What happens after the diagnosis?

After the diagnosis is confirmed, your pathology report is reviewed together with your imaging and overall health, usually by a team that includes head and neck surgeons, radiation oncologists, medical oncologists, and pathologists. The report does not decide treatment on its own, but several of its findings shape the options the team will discuss with you.

Surgery to remove the tumor, sometimes with removal of neck lymph nodes, is the main treatment for most oral cavity cancers that can be completely removed. After surgery, findings such as positive or close margins, extranodal extension, involved lymph nodes, perineural invasion, and more advanced tumor stage may lead the team to recommend radiation, sometimes combined with chemotherapy. For cancer that cannot be removed, has returned, or has spread, treatment may include radiation, chemotherapy, and immunotherapy.

Supportive care is part of treatment throughout. This includes a dental assessment before radiation, nutrition support, speech and swallowing therapy, and help with stopping tobacco and alcohol. Follow-up involves regular examination of the mouth and neck, most closely in the first two to three years, and continues long term because of the ongoing risk of a new cancer.

Questions to ask your doctor

Where in my mouth did the cancer start, and what type of squamous cell carcinoma was it?
What was the size of the tumor, and how deeply had it grown?
What is the grade, and how much does it matter in my case?
Was perineural or lymphovascular invasion found?
Did the tumor grow into bone, the sinus, or the skin?
Were all of the surgical margins clear?
How many lymph nodes were removed, and how many contained cancer?
Was extranodal extension present?
What are my pT and pN categories, and what is my overall stage?
Was PD-L1 testing done, and what did it show?
Is radiation or chemotherapy being considered after surgery?
How will my speech, swallowing, and dental health be supported?
How often will I be followed, given the risk of a new cancer developing?