Primary Intraosseous Carcinoma (PIOC), NOS: Origin from cyst lining, immunohistochemical profile and review of the literature

Introduction

Primary intraosseous carcinoma, NOS (PIOC) represents a unique subset of central carcinomas of the jaws. They're predominantly found in older males, primarily affect the posterior mandible and are thought to arise from odontogenic cysts and rests of odontogenic epithelium. The diagnosis of PIOC requires exclusion of metastases or extension of gingival, alveolar or antral squamous cell carcinomas into the jaw. In the literature, these carcinomas were associated with cysts and were typically moderately differentiated. We present 10 cases and their immunohistochemical profiles to elucidate potential diagnostic markers.

Materials and Methods

Ten cases of PIOC were identified in the OPL, Inc./NYPQ from 1997-2023. Immunohistochemical staining with CK 14, CK 19, p40, and p53 was performed.

Results

All 10 PIOCs were associated with a cyst. Two arose in keratinizing cysts. All 10 showed diffuse strong cytoplasmic expression for CK14 and nuclear expression for p40 in the cyst and tumor. CK19 was expressed in 7 of 9 cases, frequently confined to the dysplastic cyst lining and less differentiated tumor cells. The 2 cases diagnosed as arising in keratinizing cysts did not express CK19. 9 of 10 cases showed p53 nuclear expression.

Conclusion

This study provides insights into PIOC staining profiles. A correlation between CK19 and p53 positivity and poor prognosis and higher tumor grade has been suggested in oral soft tissue squamous cell carcinomas. Interestingly, CK19 positivity was observed in our non-keratinizing cysts but absent in keratinizing cysts and most obvious in our less differentiated tumors, also suggesting a potential role in the differentiation process of these tumors. In contrast, CK14 was consistently positive in both normal and dysplastic cyst linings, highlighting its broader expression in odontogenic tissues. Further research with larger sample sizes is necessary to validate these findings and explore the implications of CK19 in the prognosis of PIOC.