CARTILAGENOUS METAPLASIA IN ODONTOGENIC KERATOCYST (OKC): CASE SERIES AND IMMUNOHISTOCHEMICAL ANALYSIS

Abstract

Cartilaginous metaplasia in the wall of an OKC is an established yet rare occurrence. It is important to recognize this feature to avoid misdiagnosis as a chondroid tumor. We describe the largest series of cases with the objective to quantify the clinicopathologic features and to elucidate the nature of the cartilage. Fourteen lesions in 13 patients (1 recurrence) of OKCs exhibiting cartilaginous metaplasia in the wall were identified between 1997 and 2016. Immunohistochemical (IHC) analysis was performed on two cases. Eight of 13 cases occurred in the maxilla with 4 occurring anteriorly and 2 involving the maxillary sinus. Five cases occurred in the mandible, 3 anteriorly, including the recurrence. The average age was 55 with a range of 16 to 86 years old. Ten of 13 cases occurred in males. All 3 female cases occurred in the anterior maxilla. The chondroid areas were frequently identified in zones of inflammation near the OKC lining. The proportion of cartilage to cyst was variable. IHC for p63, GFAP, EMA, CK5/6, and actin were performed on two cases to elucidate the nature of the chondroid material. CK5/6, EMA, and p63 positivity was localized to the epithelial lining. GFAP and actin were negative in the cartilaginous areas. Our findings suggest that compared with conventional OKCs, there is a slight increase in age and predilection for the anterior jaws when cartilaginous metaplasia is observed. GFAP negativity suggests that the chondroid material may not represent actual cartilage. Cartilaginous metaplasia in the walls of OKCs should not be mistaken for a cartilaginous neoplasm.