Orthokeratinized odontogenic cysts are developmental cysts that occur in the jaw that account for approximately 7%–17% of all cysts in the jaws. Studies have shown that malignant transformation of odontogenic cysts most often occurs in inflammatory cysts, such as periapical cysts, but malignant transformation of orthokeratinized odontogenic cysts has also been reported. In this report, we present an uncommon case of squamous cell carcinoma arising from an orthokeratinized odontogenic cyst.

A rare case of primary intraosseous squamous cell carcinoma(PISCC) arising from lining epithelium of a dentigerous cyst is described. The case occurred at the left mandibular 3rd molar region in a 56-year-old Japanese woman. Clinical observation revealed cyst formation with an impacted 3rd molar, a common finding in dentigerous cyst, in the left mandible. Histopathologically, the lining epithelium of the cyst demonstrated transition from epithelial dysplasia to invasive squamous cell carcinoma(SCC). This case was diagnosed as PISCC arising from lining epithelium of a dentigerous cyst.

The dentigerous cyst(DC) and giant cell granuloma(GCG) in the jaws are well known entities that have been extensively reviewed. However, a search of the literature failed to reveal simulataneous occurrence of these two lesions. We describe a case of DC displaying foci of GCG-like lesion of a 11-year-old Korean girl. The lesion exhibited the characteristic histologic features of DC, which included a lining epithelium with underlying fibromyxoid stroma. The most intersting aspect of this lesion, however, was the presence of a prominant histologic component that resembled GCG. The most probable diagnosis was GCG-like lesion in association with a DC.