Keratocystic odontogenic tumor (KZOT) (ICD-10: K09.0 – Developmental odontogenic cysts) has been classified as a head and neck tumor by the World Health Organization (WHO) since 2005. Prior to that, the term keratocyst was used, but it did not do justice to the characteristics of this condition.
Histologically (by fine tissue), KZOT, like ameloblastoma, belongs to the odontogenic epithelial tumors with odontogenic ectomesenchyma with or without hard substance formation. KZOT is most commonly found in the mandible (5-83%), preferentially in males. The most frequent localizations are the bone in the region of the posterior molars and the ascending mandibular branch. Overall, KZOT is the second most common tumor of odontogenic origin after ameloblastoma.
Gender distribution: Males are more frequently affected than females (2:1).
Frequency peaks: age peaks are between the 10th and 40th, and between the 50th and 70th years of age.
Symptoms – Complaints
A keratocystic odontogenic tumor often grows unnoticed, and often KZOT is suspected incidentally during routine radiographic examinations at the dentist.
Usually, due to the lack of symptoms, a large finding is already present at the time of diagnosis. Often, the KZOT is so large that the bone is weakened and thus at risk of fracture.
A KZOT is characterized by aggressive growth and high recurrence rates (recurrence of the tumor).
Pathogenesis (disease development) – etiology (causes)
It is an odontogenic tumor that originates from the tissues of origin of tooth formation. Exactly how the tumor develops is not clear. It is thought to form from rudiments (remnants) of the dental crest. In the context of the so-called Gorlin-Goltz syndrome, multiple keratocystic odontogenic tumors occur, as well as the formation of basaliomas. However, this disease is an exception; in most cases, keratocystic odontogenic tumors occur solitarily.
Consequential diseases
Very rarely, malignant degeneration occurs, which means that KZOT can develop into squamous cell carcinoma.
Diagnostics
The diagnosis is often an incidental finding during a routine radiographic examination by the dentist.
Radiographic findings do not allow differentiation from ameloblastoma. A definitive diagnosis can only be made after histologic examination of the removed tumor or a specimen.
Therapy
Therapy includes complete removal of the KZOT. What makes the tumor so difficult to remove are the so-called daughter or satellite cysts. Small strands of cells grow from the KZOT into the surrounding bone and set metastases (small daughter tumors). These are barely visible to the naked eye and are often not completely resected despite careful tumor removal. As a result, recurrences are common.
In order to remove microcysts as well, the resulting bone cavity is often milled out. The resulting defect in the bone can be filled with bone substitute material or autologous bone. Sometimes the defect is so large that bone continuity must be interrupted by removing the KZOT along with the remaining thin bone. This is the only therapy that does not cause recurrences even after many years.
The continuity of the bone is then restored by means of osteosysthesis plates or by means of bone graft.
Follow-up after removal of a KZOT should initially include annual radiographic examinations. It is recommended that these be performed for at least five years. However, recurrences can still occur significantly later.