THE EXPRESSION OF P16INK4A IN ODONTOGENIC CYSTS AND TUMORS

P16 is a tumor suppressor protein that retards cell cycle progression from G1 to S phase. Prior studies have evaluated p16 expression in odontogenic keratocyst (OKC) and ameloblastoma (AB), but data regarding other odontogenic cysts and tumors has been sparse. With IRB approval, approximately 5 cases each of the following were identified from archives of the UF Oral Pathology Biopsy Service (2005–2015): benign incidental odontogenic rest (IOR), dentigerous cyst (DC), lateral periodontal cyst (LPC), calcifying odontogenic cyst (COC), glandular odontogenic cyst (GOC), OKC, orthokeratinized odontogenic cyst (OOC), adenomatoid odontogenic tumor (AOT), calcifying epithelial odontogenic tumor (CEOT), and AB. All cases were submitted for p16INK4a immunohistochemically testing. The results were scored and evaluated as follows: nuclear and cytoplasmic staining of <5% cells (score 0), 5%–25% (score 1), 25%–50% (score 2), >50% (score 3). The entities with highest rates of moderate to strong staining (score 2–3) were in decreasing order: GOC (100%), LPC (100%), AB (91%), IOR (75%), COC (60%), OKC (40%), OOC (20%), AOT (20%), DC (20%), and CEOT (0%). No significant difference in p16 staining was noted between odontogenic cysts versus tumors (chi-square, P =.540). When comparing lesions with higher recurrence rates (over 25% as reported in the literature) versus lesions with low recurrence rates (under 25%), higher recurrence correlated to significantly higher p16 positivity (chi-square, P = .002). This study exhibits an association between increased p16 positivity and odontogenic lesions with higher recurrence rates. Further investigation with a larger sample size along with other clinical factors and p16 expression may help explain the clinical behavior of some odontogenic lesions.