HPV-associated Squamous Cell Carcinoma of the Oropharynx: Understanding Your Pathology Report

Section Editor: Jason Wasserman MD PhD FRCPC
July 26, 2026

HPV-associated squamous cell carcinoma is a type of cancer that develops in the oropharynx, the part of the throat behind the mouth. The oropharynx includes the tonsils, the base of the tongue (the back third of the tongue), the soft palate, and the back wall of the throat. The cancer starts in squamous cells, the flat cells that line this part of the throat.

“HPV-associated” means the cancer is caused by a lasting infection with a high-risk type of human papillomavirus (HPV), most often HPV type 16. This matters a great deal. HPV-associated cancer of the oropharynx behaves quite differently from cancers caused by tobacco and alcohol. It tends to affect younger people, often those with little or no history of smoking or drinking, and it responds much better to treatment. Because of this, it has its own staging system, separate from the one used for other head and neck cancers, and the outlook is considerably better.

It is worth noting that the oropharynx is not the same as the oral cavity, meaning the mouth itself, which includes the lips, the front two-thirds of the tongue, the gums, and the hard palate. Cancers in these two areas behave differently and are managed separately. If your report describes a cancer of the mouth, the article on squamous cell carcinoma of the oral cavity applies.

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

What causes HPV-associated squamous cell carcinoma of the oropharynx?

HPV-associated squamous cell carcinoma of the oropharynx is caused by a lasting infection with high-risk HPV, most commonly HPV type 16. HPV is a very common virus spread through intimate contact, including oral contact. Most sexually active adults are exposed to it at some point, and in the large majority the immune system clears the infection within a year or two without any lasting effect.

In a small number of people, the virus is not cleared. When it persists, it inserts its genetic material into the DNA of the squamous cells lining the oropharynx and switches off the proteins that normally stop cells from dividing when they should not. With those controls disabled, the cells grow without restraint, and over many years this can lead to cancer.

Two points follow from this. First, because HPV damages cells in a different way from tobacco smoke, these cancers usually develop without a visible precancerous patch beforehand, which is one reason the tumor is often small and hidden when it is found. Second, the HPV vaccine, given before exposure to the virus, is highly effective at preventing the infections that cause these cancers. The vaccine cannot treat an infection you already have, but it may be relevant for family members who have not been vaccinated.

What are the symptoms of HPV-associated squamous cell carcinoma of the oropharynx?

The most common first sign of HPV-associated squamous cell carcinoma of the oropharynx is a painless lump in the neck, which is cancer that has spread to a lymph node. In many cases the original tumor in the throat is very small or hidden deep within the tonsil, so the neck lump is the only thing that can be seen or felt. Other symptoms may include:

A sore throat that does not go away
Pain or difficulty swallowing
Ear pain on one side that is not caused by an ear infection
A feeling of fullness or something stuck in the throat
Voice changes
Unexplained weight loss or tiredness

A painless neck lump that lasts more than a few weeks should always be examined by a doctor, even in someone who has never smoked.

How is the diagnosis made?

The diagnosis of HPV-associated squamous cell carcinoma of the oropharynx is made when a pathologist examines a tissue sample under the microscope. Because the tumor in the throat is often small or hidden in the tonsil, the diagnosis is frequently made first from a biopsy of an enlarged lymph node in the neck, either by fine needle aspiration or by removing the node. Tissue from the tonsil or base of the tongue is usually obtained afterward to confirm where the cancer started.

Under the microscope, the pathologist looks for squamous cells that have broken through the epithelium, the surface lining, and grown into the tissue beneath. This cancer typically has a nonkeratinizing appearance, meaning the cells produce little or no keratin and look relatively uniform. This is quite different from tobacco-related cancers, which usually produce abundant keratin. Testing for HPV, described in the next section, is required to confirm the cancer is HPV-associated. Once the diagnosis is confirmed, imaging such as a CT scan, MRI, or PET-CT shows how far the tumor extends and which lymph nodes are involved.

p16 and HPV testing

Every squamous cell carcinoma of the oropharynx is tested for HPV, because the result determines which staging system is used and what outcome to expect. The testing is done on the tumor tissue, and the results appear on your pathology report as one or more of the following:

p16: positive. p16 is a protein that builds up in large amounts inside cells infected with high-risk HPV, so it is used as a stand-in marker for the virus. It is measured using immunohistochemistry, a test that uses antibodies to detect specific proteins in tissue. A positive result means strong staining in at least 70% of the tumor cells. Your report may word this as “p16 positive” or “strong and diffuse p16 expression.” This is the expected result for this diagnosis, and for tumors of the oropharynx it is usually all that is needed.
HPV in situ hybridization: positive. This test finds the virus’s genetic material directly inside the tumor cells. It is more specific than p16 and may be added when the p16 result is borderline.
HPV PCR: positive. Another test that detects the virus directly and can identify the specific type, most often HPV 16.

Not every case needs all three. A positive p16 result together with invasive squamous cell carcinoma under the microscope is generally enough to establish the diagnosis, so a report showing only p16 is not incomplete. If your report shows a negative p16 result, the HPV-independent squamous cell carcinoma article applies to you.

Is HPV-associated squamous cell carcinoma given a histologic grade?

No. Unlike most other cancers, HPV-associated squamous cell carcinoma of the oropharynx is not assigned a histologic grade. If you are looking for a grade on your report and cannot find one, nothing has been left out.

The reason is that grading works by measuring how far tumor cells have drifted from normal, and in this cancer nearly all tumors look similar under the microscope and behave similarly regardless. Grade therefore does not add useful information here, unlike in tobacco-related squamous cell carcinoma where it does. Your report may simply describe the tumor as nonkeratinizing, or state that grading is not applicable.

Tumor extension into nearby structures

Your report will describe whether the tumor has grown beyond where it started into anything nearby. HPV-associated squamous cell carcinoma usually begins in the lining of the tonsil or the base of the tongue, within the small pits called crypts where HPV infects the cells. As it grows, it can extend into the walls of the throat or the soft tissue of the neck, and larger tumors may reach the larynx (voice box), the deep muscles of the tongue, the hard palate, or the mandible (lower jaw). Growth into these structures raises the tumor stage and is one of the findings the treatment team weighs when planning care.

Perineural invasion

Perineural invasion means cancer cells are growing along or around a nerve. Nerves provide a path that cancer cells can follow beyond the visible edge of the tumor. Your report will state whether perineural invasion is present or absent. When present, it is associated with a higher chance of the cancer returning, and it is one of the findings that may lead the treatment team to consider radiation after surgery.

Lymphovascular invasion

Lymphovascular invasion means cancer cells have entered a small blood vessel or lymphatic channel near the tumor. These vessels can carry cancer cells to the lymph nodes or, less often, to distant organs. Your report will state whether it is present or absent, and when present it is considered an adverse finding that may influence the treatment options discussed with you.

Surgical margins

Margins are the cut edges of the tissue removed during surgery. The pathologist inks these edges and examines how close the tumor comes to each one.

Negative (clear) margin. No cancer cells at the inked edge. This suggests the tumor was removed completely.
Close margin. Cancer cells come within a few millimeters of the edge without reaching it. This may influence whether radiation is discussed after surgery.
Positive (involved) margin. Cancer reaches the inked edge, meaning some may remain. This often leads to a discussion about further surgery or radiation.

Lymph nodes

Lymph nodes are small immune organs that filter fluid draining from the tissues. HPV-associated squamous cell carcinoma of the oropharynx spreads to the lymph nodes in the neck early and often, so a neck dissection to remove a group of these nodes is usually part of treatment. 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 30. For this cancer, the number of involved nodes is what determines the nodal stage.
The size of the largest deposit of cancer. Measured in millimeters.
Extranodal extension. This means cancer cells have broken through the outer capsule of a lymph node into the surrounding tissue.

Two points here often surprise patients, and both are reassuring. First, cancer in the lymph nodes is very common in this disease, present in most people at the time of diagnosis, and because of the favorable way this cancer behaves, involved nodes do not carry the same weight they would in a tobacco-related cancer. Second, extranodal extension is reported when it is found, but unlike in other head and neck cancers it does not change the pathologic stage of an HPV-associated oropharyngeal cancer. It may still be taken into account when planning treatment, so it is worth discussing with your doctor if it appears on your report.

PD-L1

PD-L1 is a protein that some cancer cells display on their surface to avoid being attacked by the immune system. Immunotherapy drugs called checkpoint inhibitors, such as pembrolizumab (Keytruda) and nivolumab (Opdivo), block this signal so the immune system can recognize and attack the cancer.

PD-L1 testing is not needed to make the diagnosis. It is generally performed when the cancer cannot be removed by surgery, has returned after treatment, or has spread to distant parts of the body. The result is reported as a Combined Positive Score, or CPS, a number that 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. You can read more in the article on PD-L1 testing in cancer.

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.

HPV-associated oropharyngeal cancer has its own staging system, separate from the one used for all other head and neck cancers. This exists because the disease responds so much better to treatment that applying the usual system would place most patients at a stage far more serious than their actual outlook. Under this system most people with this cancer are stage I or stage II, even when several lymph nodes contain cancer.

Tumor stage (pT)

pT0. No tumor was found in the throat, even though cancer was confirmed in a lymph node. This happens in this disease because the original tumor can be very small, and it does not mean anything was missed.
pT1. Tumor 2 cm or smaller.
pT2. Tumor larger than 2 cm but not more than 4 cm.
pT3. Tumor larger than 4 cm, or extending to the surface of the epiglottis.
pT4. Tumor has grown into nearby structures such as the larynx, the deep muscles of the tongue, the hard palate, or the jawbone. Unlike other head and neck cancers, this category is not divided further, because doing so does not change the expected outcome.

Nodal stage (pN)

The nodal stage for this cancer is based only on the number of lymph nodes containing cancer. The size of the nodes, which side of the neck they are on, and whether extranodal extension is present are all left out, because none of them changes the outlook enough to affect the stage.

pN0. No cancer found in any lymph node.
pN1. Cancer found in 4 or fewer lymph nodes.
pN2. Cancer found in more than 4 lymph nodes.

There is no pN3 category in the pathologic staging of this cancer. 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 HPV-associated squamous cell carcinoma of the oropharynx?

Prognosis means the likely course and outcome of a disease. For HPV-associated squamous cell carcinoma of the oropharynx, the outlook is considerably better than for head and neck cancers not caused by HPV at a comparable stage. This favorable behavior is the single most important feature of this diagnosis and the reason it has a separate staging system.

Reported five-year survival is often above 80% for cancer that has not spread to distant parts of the body. Many people are cured, and long-term survival is common even when several lymph nodes contain cancer. These figures are averages drawn from large groups of patients and describe general patterns rather than predicting what will happen for any one person.

Because the outlook is so favorable, researchers are actively studying whether treatment can be safely reduced for some patients, using lower doses of radiation or less extensive surgery, without lowering the chance of cure. This approach is called de-escalation, and clinical trials of it are ongoing. Whether it is appropriate for you is a reasonable question for your treatment team.

Within this generally favorable picture, the findings associated with a somewhat higher risk of the cancer returning are extranodal extension, positive or close surgical margins, perineural invasion, and tumor growth beyond the oropharynx. Tobacco use also worsens the outlook even in HPV-associated disease, and people who have never smoked, or smoked very little, tend to do best. Stopping tobacco is a step worth taking at any point.

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.

For many people the main treatments are surgery, radiation, or a combination. Early tumors may be removed through the mouth without an external incision, using transoral robotic surgery or transoral laser microsurgery, or treated with radiation alone. For larger tumors or when lymph nodes are involved, radiation combined with chemotherapy may be discussed. For cancer that has returned or spread, options include chemotherapy, the targeted drug cetuximab, and immunotherapy.

Supportive care runs alongside treatment and includes a dental assessment before radiation, nutrition support, and therapy for swallowing and speech. Follow-up involves regular examination and imaging, most intensively in the first two to three years, when recurrence is most likely.

Questions to ask your doctor

Was my cancer confirmed as HPV-associated, and what did the p16 test show?
Where in my oropharynx did the cancer start?
What was the size of the tumor, and did it grow into any nearby structures?
My report has no grade. Is that expected for this cancer?
How many lymph nodes contained cancer?
Was extranodal extension present, and does it affect my treatment even though it does not change my stage?
What are my pT and pN categories, and what is my overall stage?
Were the surgical margins clear?
Was perineural or lymphovascular invasion found?
Was PD-L1 testing done, and what was the CPS result?
Am I a candidate for a reduced-intensity (de-escalation) treatment approach, or a clinical trial?
How will my swallowing, speech, and dental health be supported during and after treatment?
How often will I be followed, and for how long?
Is HPV vaccination relevant for anyone in my family?