Early Malignant Transformation of Radicular Cyst: Two Cases and Literature Review of the Recent Decade 

(Pages: 57-64)

Satoshi Murakami1, Katsumitsu Shimada1, Rita Rani Roy2 and Hiromasa Hasegawa2

1Department of Oral Pathology, Matsumoto Dental University, Shiojiri, Japan; 2Hard Tissue Pathology Unit, Graduate School of Oral Medicine, Matsumoto Dental University, Shiojiri, Japan

DOI: https://doi.org/10.30576/2414-2050.2020.06.10



Abstract: Primary intraosseous carcinoma, NOS (PIOC) rarely occur de novo or secondary from odontogenic cysts including radicular cyst (RC). Although some PIOCs arisen from RC have been reported, many cases are hardly able to ascertain the origins because cyst walls were completely destructed. In order to confirm the risk of carcinogenesis in RC, we reviewed our archived cases of RC and retrieved reported cases published during the recent decade using PubMed Mesh. We found 2 cases with atypical-proliferating foci among 900 cases diagnosed as RC from our archives. Case 1 showed atypical cell proliferation with marked cytological atypia including multipolar mitosis, increased Ki67 positivity and p53 overexpression. Case 2 showed irregular projections and invaginations of thickened, keratinized and bland squamous cells with a pushing border, and overexpression of cytokeratin 17 and GLUT-1. Cyst walls of both cases were partially lined by intact non-keratinized epithelium supported by markedly inflamed connective tissue. Consequently, we diagnosed these atypical lesions as malignant transformation in the pre-existing lining epithelium. Our literature review during the recent decade revealed that PIOCs arisen from RC including residual cyst accounted for 9 % of PIOCs arisen from odontogenic cyst, in contrast to 60 % between 1938 and 2010. Although the risk of malignant change of RC is very low as 0.2% in our study, we have to pay careful attention to it.

Keywords: Primary intraosseous carcinoma NOS, malignant transformation, radicular cyst, in situ carcinoma, immunohistochemistry.