What causes okc cysts

What is an Odontogenic Keratocyst (OKC)?

An odontogenic keratocyst (OKC), previously known as a keratocystic odontogenic tumor (KCOT), is a cystic lesion of the jaw that originates from the odontogenic epithelium. This means it develops from the tissues that are involved in tooth formation. OKCs are considered developmental cysts, meaning they arise from remnants of the dental lamina, a structure present during embryonic development that gives rise to teeth. While they are cysts, their aggressive behavior, high recurrence rate, and potential for rapid growth have led some to classify them as benign but locally aggressive tumors.

Causes and Development of OKC Cysts

The primary cause of OKC cysts lies in the remnants of the dental lamina. During tooth development, the dental lamina is a band of epithelial tissue that grows from the oral epithelium into the underlying mesenchyme. It is responsible for initiating the formation of tooth buds. After the tooth germ has developed, the dental lamina usually regresses and disappears. However, sometimes, small islands or remnants of this lamina persist within the jawbone.

These persistent rests of the dental lamina can proliferate and undergo cystic changes, leading to the formation of an OKC. The exact triggers for this proliferation and cystic transformation are not fully understood, but factors such as inflammation, trauma, or genetic predispositions may play a role. The lining of the cyst is typically characterized by a thin, parakeratinized stratified squamous epithelium, which is a key histological feature that differentiates it from other types of jaw cysts.

Location and Characteristics

OKCs are most frequently found in the posterior part of the mandible (lower jaw), particularly in the angle and ramus regions. They can also occur in the anterior mandible, maxilla (upper jaw), and even in the soft tissues of the oral cavity, although this is less common. OKCs can grow to considerable sizes, often expanding the bone and causing thinning or perforation of the cortical plates. Despite their potential for significant growth, they are often asymptomatic in their early stages and are typically discovered incidentally during routine dental examinations or radiographic surveys performed for other reasons.

When symptoms do occur, they can include painless swelling, pain, discharge, malocclusion (misalignment of teeth), or the eruption of an associated unerupted tooth. The internal structure of an OKC is often filled with keratinous material, which is a cheesy or waxy substance.

Association with Gorlin-Goltz Syndrome

A significant aspect of OKC cysts is their association with Gorlin-Goltz syndrome, also known as nevoid basal cell carcinoma syndrome (NBCCS). This is a rare genetic disorder that affects multiple systems in the body. Approximately 5-15% of individuals with OKCs have this syndrome, and conversely, about 70-90% of individuals with Gorlin-Goltz syndrome will develop one or more OKC cysts. The syndrome is characterized by a predisposition to various cancers, particularly basal cell carcinomas, and skeletal abnormalities.

The genetic mutation responsible for Gorlin-Goltz syndrome is in the PTCH1 gene, a tumor suppressor gene. The presence of OKCs in a patient, especially multiple OKCs or OKCs occurring at a young age, should prompt consideration for screening for Gorlin-Goltz syndrome.

Recurrence and Management

One of the most challenging aspects of managing OKC cysts is their high rate of recurrence. After surgical removal, OKCs can reappear in 10% to 60% of cases. This high recurrence rate is attributed to several factors, including the cyst's thin, friable lining that can easily fragment during surgery, the presence of satellite cysts within the jawbone, and the potential for the epithelial rests to proliferate again. Complete surgical excision with adequate margins is crucial for reducing recurrence risk. However, even with meticulous surgery, long-term follow-up with regular radiographic examinations is essential to detect any signs of recurrence early.

Treatment typically involves surgical enucleation (complete removal of the cyst) or marsupialization (creating an opening in the cyst to allow it to drain and shrink). In some cases, particularly for larger cysts or those with a high risk of recurrence, more extensive surgery such as a marginal mandibulectomy (removal of a portion of the jawbone) might be considered. Post-operative management and vigilant follow-up are key components of successful treatment to minimize the risk of recurrence and prevent potential complications.

Distinguishing from Other Cysts

OKCs must be distinguished from other types of odontogenic cysts, such as dentigerous cysts (which form around the crown of an unerupted tooth) and radicular cysts (which form at the root apex of a non-vital tooth). Histopathological examination of the cyst lining is the definitive method for diagnosis, with the characteristic parakeratinized epithelium being the hallmark of an OKC.