English

Abstract

Primary intraosseous carcinoma (PIOC) previously named as primary intraosseous squamous cell carcinoma (PIOSCC), derived from an odontogenic keratocyst (OKC) is a locally aggressive rare malignant neoplasm of the jaws with poor prognosis. The incidence of carcinomas arising from odontogenic cysts was reported to be approximately 1 – 2 / 1000. The knowledge of the histopathological features of PIOC allows accurate and early diagnosis of the lesion so that an early and appropriate treatment can be instituted for better prognosis. Primary intraosseous squamous cell carcinoma (PIOSCC) is a carcinoma arising from the central bone without any initial connection to various epithelia.1 In 2017, according to WHO classification of tumours, it was renamed as primary intraosseous carcinoma (PIOC).2 According to the current WHO classification, PIOC is a central jaw carcinoma that cannot be classified as any other condition and presumably has developed from odontogenic cysts or other benign precursors. The most common odontogenic cysts having a significant probability of malignant transformation are dentigerous cysts, residual periapical cysts, and odontogenic keratocysts (OKCs).3,4 The transition from this benign cystic lining to squamous cell carcinoma may remain clinically undetected, and the delay in diagnosis has a significant influence on treatment and prognosis.5 Therefore, the initial radiographic features of PIOC arising from an OKC (PIOC ex - OKC) are similar to those of benign odontogenic tumours or cysts, including conventional OKCs.4 Hence, it is mandatory to further investigate it histopathologically for final diagnosis and proper treatment plan. Malignant changes in OKCs have been rarely reported. To the best of our knowledge, very few cases of PIOC ex - OKC have been described in the literature. The purpose of this article is to report a case of PIOC that originated from an OKC and to shed light on the process of malignant transformation of this rare lesion. Here, is the case report describing an extremely rare case of PIOC of the maxilla derived from an OKC in a 45 - year - old female patient.