Radicular Cyst of the Jaw: Understanding Your Pathology Report

by Jason Wasserman MD PhD FRCPC
May 3, 2026

A radicular cyst — also called a periapical cyst or apical periodontal cyst — is a noncancerous, fluid-filled growth that develops at the tip of a tooth’s root. It is the most common type of odontogenic cyst (a cyst arising from tooth-related tissues) and is almost always caused by long-standing infection or injury inside the tooth. The cyst itself is harmless, but it indicates that the affected tooth is no longer alive and that the surrounding bone is being slowly damaged by chronic inflammation.

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

What causes a radicular cyst?

Every tooth contains a soft inner core called the pulp, which holds the nerve and blood vessels that keep the tooth alive. When the pulp is damaged — most often by deep dental decay, but also by trauma to the tooth, a cracked tooth, or previous dental work — the nerve can die. Bacteria from the mouth then travel through the dead pulp and out the tip of the root, where they trigger a long-lasting immune reaction in the surrounding bone. This chronic inflammation eventually awakens small clusters of cells called the rests of Malassez — leftover cells from the original development of the tooth root that normally sit quietly in the surrounding tissue. As these cells multiply in response to the inflammation, they form a hollow, fluid-filled cavity lined by squamous (skin-like) cells: a radicular cyst.

The most common underlying causes are:

Dental caries (tooth decay) — Deep decay that reaches the pulp and kills the nerve. By far the most common cause.
Dental trauma — A blow to a tooth that disrupts the blood supply to the pulp. The nerve may die slowly over months or years.
Cracked tooth — A fracture that allows bacteria to reach the pulp.
Previous dental work — A failed root canal or a deep restoration that placed stress on the pulp.

What are the symptoms of a radicular cyst?

Many radicular cysts cause no symptoms and are discovered by chance on a routine dental X-ray. When symptoms do occur, they tend to develop slowly:

Swelling — A firm bump along the gum or jawline near the affected tooth.
Discomfort or pain — Often mild and intermittent. Pain is usually only severe if the cyst becomes infected.
Tooth sensitivity — The affected tooth and sometimes neighboring teeth may feel tender to pressure or biting.
Tooth discoloration — A tooth with a dead nerve may turn gray or yellow over time.
Tooth displacement — Larger cysts can push nearby teeth out of position.
Drainage — A small opening (sinus tract) may form on the gum, occasionally releasing pus or fluid into the mouth.

Very large or long-standing cysts can thin the surrounding bone and, rarely, weaken the jaw enough to be visible as a swelling on the outside of the face.

How is the diagnosis made?

The diagnosis is made after a tissue sample is examined under the microscope by a pathologist. A radicular cyst is usually first suspected on a dental X-ray, which shows a well-defined dark (radiolucent) area at the tip of a tooth root. The dentist or endodontist may perform additional tests — including tapping on the tooth, applying cold to test the nerve, and measuring the depth of any gum pockets — to confirm that the tooth is no longer alive. The cyst itself is removed during one of two procedures: a tooth extraction, in which the cyst is sometimes pulled out attached to the root tip, or an apicoectomy (also called a root-end resection), a small surgery in which the tip of the root is removed along with the surrounding cyst tissue while the rest of the tooth is preserved. The removed tissue is then sent to the laboratory for examination.

Under the microscope, the pathologist looks for an open space (the cyst cavity) lined by stratified squamous epithelium of variable thickness. Below the lining, the wall of the cyst is made of fibrous (scar-like) connective tissue containing a heavy mix of inflammatory cells, especially lymphocytes and plasma cells. Cholesterol clefts — slit-like spaces left behind by cholesterol crystals that have leaked from broken-down cells — are commonly seen in the cyst wall and are a helpful clue to the diagnosis. The combination of these microscopic features, the X-ray appearance, and the clinical history of a non-vital tooth confirms the diagnosis.

Periapical granuloma versus radicular cyst

Two conditions sit at opposite ends of the same disease process: periapical granuloma and radicular cyst. Both develop at the tip of a non-vital tooth root and look almost identical on a dental X-ray. The difference is microscopic. A periapical granuloma is a collection of inflammation and scar tissue without a true cyst cavity. A radicular cyst is the same lesion at a more advanced stage — chronic inflammation has triggered the rests of Malassez to form a hollow, epithelium-lined cavity. Because the X-ray appearances overlap, the only way to tell the two apart with certainty is to examine the tissue under the microscope. Treatment is similar for both, and both usually heal completely once the underlying tooth problem is addressed.

Residual cyst

If a radicular cyst is not fully removed when the affected tooth is extracted, the cyst can persist in the bone. This is called a residual cyst. It often comes to attention years later when a dark area is noticed on a routine dental X-ray, sometimes long after the patient has forgotten that a tooth was ever removed from that location. Under the microscope, a residual cyst looks identical to a radicular cyst. Treatment is straightforward removal.

What is the prognosis?

The outlook for a radicular cyst is excellent. It is benign and does not develop into cancer. Once the underlying tooth problem is treated and the cyst is removed, the bone almost always fills in completely over the following 6 to 12 months, and the area returns to normal on follow-up X-rays. Recurrence is uncommon when the cyst has been completely removed. Long-term complications are rare.

What happens after the diagnosis?

Treatment of a radicular cyst is led by a dentist, endodontist (a dentist who specializes in root canals), or oral and maxillofacial surgeon, depending on the size and location of the cyst and the condition of the affected tooth. The goal is twofold: remove the cyst itself and address the underlying problem in the tooth so that the inflammation does not return.

Root canal therapy — When the affected tooth can be saved, the dentist or endodontist removes the dead pulp, cleans and shapes the root canal system, and seals it. For small cysts, this alone is often enough — the inflammation resolves and the bone heals on its own over several months.
Apicoectomy (root-end surgery) — A small surgical procedure in which the tip of the root and the cyst are removed through the gum while the rest of the tooth is preserved. Used when a previous root canal has failed or when the cyst is large.
Tooth extraction with curettage — When the tooth cannot be saved, it is removed, and the cyst is scraped out (curetted) at the same operation. The empty socket usually heals well, and the missing tooth can later be replaced with an implant or bridge.
Marsupialization — Rarely used for very large cysts that involve important structures (such as the sinus or a major nerve). The cyst is opened and allowed to slowly shrink before complete removal.

Follow-up X-rays are typically obtained at 6 and 12 months to confirm bone healing. No further treatment is needed once the area has filled in.

Questions to ask your doctor

Which tooth is the cyst associated with, and is it still alive?
Was the cyst completely removed during my procedure?
Do I need a root canal, an apicoectomy, or an extraction?
If the tooth needs to be removed, what are my options for replacing it?
How will we know that the bone is healing properly, and what is the timeline for follow-up X-rays?
What is the chance the cyst could come back?
Were there any unusual features in the pathology report that change the recommended treatment?
Are there any other teeth at risk that I should be watching?
Is there anything I can do to prevent another cyst from forming?