Odontogenic Keratocyst: Understanding Your Pathology Report

by Jason Wasserman MD PhD FRCPC
May 3, 2026

An odontogenic keratocyst (OKC) is a noncancerous, fluid-filled growth that develops within the bones of the jaw. It is called “odontogenic” because it arises from cells left behind during tooth formation (“odonto” means tooth, “genic” means producing). Although OKC is benign, it differs from most simple cysts in two important ways: it tends to grow along the length of the jawbone rather than expanding outward, and it is more likely to recur after surgery if not completely removed. For these reasons, OKC is treated more aggressively than most other jaw cysts.

This article will help you understand the findings in your pathology report — what each term means and why it matters for your care.

A note on the name

The name of this entity has changed over the years, and you may encounter different terms in older reports or articles:

Odontogenic keratocyst (OKC) — The current World Health Organization (WHO) name and the name most commonly used today.
Keratocystic odontogenic tumor (KCOT) — A name introduced in 2005 to reflect the aggressive behavior of these lesions and the discovery of mutations driving their growth. The WHO reverted to the older name “odontogenic keratocyst” in 2017 because most lesions behave more like a cyst than a true tumor. You may still see “KCOT” in reports written between 2005 and 2017.
Primordial cyst — A historical term, no longer in use.

All of these names refer to the same lesion.

What causes an odontogenic keratocyst?

OKCs arise from small clusters of cells that remained in the jaw after the teeth finished forming. Why these cells start to grow into a cyst is not fully understood, but the underlying genetic change that drives most OKCs has been identified. Almost all OKCs carry a mutation in a gene called PTCH1, which normally acts as a brake on the Hedgehog signaling pathway — a chemical messaging system inside cells that controls growth and tissue patterning. When PTCH1 is damaged, the brake is released, and the pathway runs continuously, telling the cyst cells to keep dividing.

In most patients, this PTCH1 mutation occurs only in the cyst itself and is not present in the rest of the body’s cells. These patients typically have a single OKC and no related health problems. In a smaller group of patients, however, the PTCH1 mutation is inherited and is present in every cell. These patients have a genetic condition called nevoid basal cell carcinoma syndrome, which is described in detail in its own section below.

Where does an odontogenic keratocyst start?

Most OKCs arise in the mandible (the lower jaw), and most of those occur near the back of the jaw, in the area of the third molars (wisdom teeth) and the rising part of the bone behind them called the ramus. Roughly 25% of OKCs occur in the maxilla (the upper jaw), most often near the back. OKCs in the front of either jaw are uncommon.

What are the symptoms of an odontogenic keratocyst?

Many OKCs cause no symptoms at all and are discovered by chance on a dental X-ray taken for another reason — often during routine dental care or before the removal of wisdom teeth. When symptoms do occur, they tend to develop slowly because the cyst grows along the bone rather than ballooning outward. Reported symptoms include:

Swelling — A firm, painless bulge along the jaw, usually toward the back.
Pain or discomfort — Often mild and intermittent, and often only present when the cyst becomes infected or presses against a nerve.
Tooth displacement — Nearby teeth may be pushed out of position, causing changes in the bite.
Loose teeth — Larger cysts can erode the bone supporting the roots of nearby teeth.
Numbness — Cysts that press on the nerve running through the lower jaw can cause numbness or tingling of the lower lip and chin.
Drainage or bad taste — Occurs if the cyst becomes infected or ruptures into the mouth.

How is the diagnosis made?

The diagnosis of an OKC is made after a tissue sample is examined under the microscope by a pathologist. Most patients first undergo an imaging study — usually a panoramic dental X-ray, often followed by a CT scan or cone-beam CT — that shows a well-defined dark space within the jawbone. The space may be a single round area or may have several connected compartments. Imaging alone cannot make the diagnosis because several other jaw lesions, including ameloblastoma and other types of odontogenic cysts, can look very similar. To confirm the diagnosis, an oral and maxillofacial surgeon performs a biopsy in which a sample of the cyst lining is removed and sent to the laboratory. In many cases, the entire cyst is removed in one operation, and the diagnosis is made on the resection specimen rather than on a separate biopsy.

Under the microscope, the pathologist looks for several specific features that together make the diagnosis. The cyst is lined by a thin, even layer of epithelium made up of squamous cells, typically only six to eight cells thick. The cells at the bottom of the lining (the basal cells) are small, dark, and lined up side-by-side in a regimented row — a pattern called palisading. The surface of the lining is covered by a thin, wavy layer of keratin (a tough protective protein) that is usually parakeratotic, meaning the surface cells still contain visible nuclei. The keratin surface often has a corrugated, washboard-like appearance. Below the lining, the cyst wall is composed of connective tissue that may show fibrosis or chronic inflammation, especially if the cyst has previously ruptured or become infected. Once the diagnosis is confirmed, imaging is used to map the cyst’s full extent and plan the operation to remove it.

Orthokeratinized odontogenic cyst — a different diagnosis

An important distinction your pathologist must make is between an OKC and a separate, less common entity called the orthokeratinized odontogenic cyst. Although the two look broadly similar, the orthokeratinized version has a thick layer of mature keratin on its surface in which the surface cells have lost their nuclei (this is called orthokeratin, the same kind of keratin found on the skin). This distinction matters because the orthokeratinized odontogenic cyst behaves much less aggressively, has a much lower recurrence rate, and is not associated with nevoid basal cell carcinoma syndrome. If your pathology report uses the term “orthokeratinized odontogenic cyst,” you have a different — and considerably less worrisome — diagnosis than OKC.

Nevoid basal cell carcinoma syndrome (Gorlin syndrome)

Nevoid basal cell carcinoma syndrome (NBCCS), also called Gorlin syndrome, is a rare inherited condition caused by a germline mutation in the PTCH1 gene — the same gene that is mutated within sporadic OKCs. “Germline” means the mutation is present in every cell of the body and can be passed from a parent to a child. Patients with NBCCS develop multiple OKCs over their lifetime, often starting in their teens, and may have several other features:

Multiple basal cell carcinomas of the skin — Often appearing earlier in life than typical sun-related basal cell carcinomas, and often in skin areas that are not heavily sun-exposed.
Palmar and plantar pits — Small pinpoint depressions on the palms of the hands and soles of the feet.
Calcification of the falx cerebri — A sheet of tissue inside the skull that becomes visible on X-ray or CT because of calcium deposits.
Skeletal abnormalities — Including bifid (split) ribs, vertebral anomalies, and a characteristic broad facial appearance.
Increased risk of medulloblastoma — A type of brain tumor that occurs more often in children with NBCCS than in the general population.

Because most patients with NBCCS are diagnosed during their teens or twenties, the appearance of an OKC at a young age, the discovery of more than one OKC, or any family history of unusual jaw cysts or early skin cancers should prompt referral to a medical geneticist or genetic counselor. Confirming the diagnosis allows the patient to be screened for other features of the syndrome, allows family members to be tested, and changes long-term follow-up. A single OKC in an older adult with no other features and no family history is unlikely to be syndrome-related.

Surgical margins

A margin is the edge of the tissue that the surgeon cuts when removing a cyst or tumor. The pathologist examines these edges under the microscope to determine whether any cyst lining reaches the cut surface. Margin status is reported in pathology reports for OKC because residual cyst lining is one of the main reasons OKCs come back.

Negative margin — No cyst lining is seen at the cut edge. This suggests the cyst was completely removed.
Positive margin — Cyst lining is seen at the cut edge of the tissue. This means small fragments of the cyst were almost certainly left behind in the bone, which raises the risk of recurrence and may prompt the surgeon to recommend additional treatment of the surgical site.

Because the cyst lining of an OKC is very thin and can be fragile, it sometimes fragments during removal — even when the surgery itself is technically complete. Margin assessment in OKC is therefore not as straightforward as in solid tumors, and the surgeon’s intraoperative findings are also taken into account when planning follow-up.

What is the prognosis?

OKC is benign and does not turn into cancer. The principal long-term concern is recurrence — the cyst growing back in the same area after surgery. Reported recurrence rates depend heavily on the type of operation performed:

Simple enucleation alone — Recurrence rates of 25–60% have been reported. This is the highest recurrence rate among the common jaw cysts.
Enucleation with adjunctive treatment — Adding a chemical treatment (such as Carnoy’s solution) or mechanical treatment (such as peripheral ostectomy, in which a thin layer of surrounding bone is also removed) reduces the recurrence rate substantially, typically to under 10–15%.
Marsupialization or decompression — Creating an opening in a large cyst to allow it to slowly shrink before complete removal. Useful for very large lesions, but may need to be combined with later definitive surgery.
Resection — Removing the affected portion of the jawbone with a margin of normal bone. Has the lowest recurrence rate (close to zero) but is rarely needed and is reserved for very large, recurrent, or aggressive cysts.

Patients with nevoid basal cell carcinoma syndrome have a higher recurrence rate than patients without the syndrome and may also develop new OKCs at other sites in the jaw. Most recurrences occur within the first 5 years after surgery, but late recurrences — even more than 10 years out — are well documented. This is why long-term imaging follow-up is recommended for all patients with an OKC.

What happens after the diagnosis?

Treatment for OKC is led by an oral and maxillofacial surgeon, often working with a dentist or prosthodontist for any later dental rehabilitation, and (when the syndrome is suspected) with a medical geneticist and dermatologist.

The mainstay of treatment is surgery, and the choice of operation depends on the size and location of the cyst, whether the patient has had a previous OKC, whether nevoid basal cell carcinoma syndrome is known or suspected, and the patient’s preferences. Options include enucleation alone, enucleation combined with peripheral ostectomy or a chemical agent, marsupialization or decompression for very large cysts, and rarely, segmental resection of the jawbone.

After surgery, regular clinical examinations and panoramic X-rays or CT scans are performed for many years to watch for recurrence — typically annually for the first several years and then less frequently after that. Patients with NBCCS may need lifelong dental imaging surveillance because new cysts can continue to develop. Dental rehabilitation, including replacement of teeth lost during surgery, is often a long-term part of recovery, especially when a large portion of the jaw was involved.

Targeted drug therapy is not currently a standard treatment for OKC, but Hedgehog-pathway inhibitors (such as vismodegib) — drugs already approved for advanced basal cell carcinoma — have been studied in patients with NBCCS who develop multiple OKCs and have shown promising results in shrinking these cysts. The use of these drugs is still considered experimental in this setting.

Questions to ask your doctor

Where exactly in my jaw is the cyst, and how large is it?
Did the pathology report confirm odontogenic keratocyst, or is it the orthokeratinized odontogenic cyst variant?
What type of operation was (or will be) performed, and why was that approach chosen?
Were the surgical margins negative, or was any cyst lining present at the cut edge?
If a margin was positive, do I need additional treatment?
What is my estimated risk of the cyst coming back?
Should I be tested for nevoid basal cell carcinoma syndrome (Gorlin syndrome)?
If I have the syndrome, what other screening do I need, and what does it mean for my children?
What is the schedule for follow-up imaging, and how long will it continue?
Will any of my teeth need to be removed, and what are my options for replacing them?
Will I have lasting numbness in my lip or chin from the surgery or the cyst itself?
Are there clinical trials I should consider, particularly if I have the syndrome and have had multiple cysts?