A keratocystic odontogenic tumor (KCOT) is a benign growth that develops within the jawbones, originating from tissue remnants involved in tooth formation. While not cancerous, it is known for its locally aggressive behavior, expanding within the bone and affecting nearby structures. This growth is classified as a developmental cyst, though its characteristics resemble those of a tumor.
These growths are most frequently found in the lower jaw, particularly near the wisdom teeth. Historically, its classification has shifted between being a cyst (odontogenic keratocyst, or OKC) and a tumor, reflecting ongoing study into its nature. Despite the name changes, its clinical behavior and management are well understood.
Symptoms and Diagnosis
Many keratocystic odontogenic tumors do not produce noticeable symptoms and are often discovered during routine dental X-rays. The tumor expands along the jawbone’s internal cavity rather than causing significant outward swelling, which is why it can become large before being detected.
When symptoms arise, they may include a painless swelling of the jaw, a change in tooth alignment, or discharge if the lesion becomes infected. Pain or numbness in the lip or chin is less common but can occur if the cyst compresses a nerve.
The diagnostic process begins with imaging. On an X-ray, a KCOT appears as a well-defined, dark area with a distinct border. A computed tomography (CT) scan provides a more detailed view of the lesion’s size and its relationship to structures like teeth and nerves.
While imaging provides strong evidence, a definitive diagnosis requires a biopsy. This involves removing a small piece of the cyst’s wall for a pathologist to examine and confirm the diagnosis.
Underlying Causes and Associated Conditions
The development of most KCOTs is linked to mutations in the PTCH1 gene. This gene functions as a tumor suppressor, and when it is inactivated by a mutation, it can lead to the uncontrolled cell proliferation that forms the cyst.
This genetic link connects KCOTs to an inherited condition known as Nevoid Basal Cell Carcinoma Syndrome (NBCCS), also called Gorlin-Goltz syndrome. The presence of multiple KCOTs, or the diagnosis of a single KCOT at a young age, is a diagnostic criterion for NBCCS. A KCOT diagnosis can be the first indication that a person has Gorlin-Goltz syndrome.
Other features of this syndrome include the development of numerous basal cell carcinomas (a type of skin cancer), skeletal anomalies of the ribs or spine, and calcification of certain brain tissues.
When a KCOT is confirmed by a pathologist, especially in a younger patient or if more than one is found, further evaluation for NBCCS is recommended. This may involve a full-body skin examination and additional imaging to check for other signs of the syndrome.
Treatment Approaches
The primary treatment for a KCOT is complete surgical removal. The specific surgical technique depends on the tumor’s size, location, and whether it is a first-time occurrence or a recurrence, with the goal of eliminating the entire lining to prevent regrowth.
A common surgical method is enucleation and curettage. The surgeon carefully separates and scoops out the entire cyst lining from the bony cavity (enucleation). Following this, the surgeon uses a curette to scrape the bone walls of the cavity to remove any microscopic remnants.
For very large KCOTs, a surgeon might first perform marsupialization. This involves creating a small surgical window into the cyst, allowing its contents to drain. This decompresses the lesion, causing it to shrink over several months, which makes its eventual removal through enucleation a safer and less invasive procedure.
In cases of very large, complex, or recurrent tumors, resection may be required. This involves removing the KCOT along with a margin of the surrounding jawbone. To reduce the likelihood of the tumor returning, surgeons may use adjuvant therapies like applying a chemical agent or using cryotherapy (freezing) to destroy residual cells.
Recurrence and Long-Term Management
A defining feature of the keratocystic odontogenic tumor is its tendency to recur after treatment. The rate of recurrence is notably higher than that of other common jaw cysts.
The main reason for recurrence is the cyst’s lining, which is exceptionally thin and friable. This delicate structure can tear during surgical removal, making it difficult to eliminate every fragment. The tumor wall can also contain microscopic satellite cysts that can be left behind and grow into a new tumor.
Due to this high potential for regrowth, long-term follow-up is part of management. After treatment, patients undergo regular monitoring with an oral and maxillofacial surgeon, which includes clinical exams and periodic imaging to watch for any signs of the tumor returning.
This surveillance period lasts for at least five years and can extend for ten or more, as recurrences can happen many years after the initial surgery. This monitoring ensures that if the KCOT returns, it is detected early when it is smaller and easier to manage.