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.

Orthokeratienized odontogenic cyst (OOC) is a comparatively unusual developmental odontogenic cyst arising from odontogenic epithelium. Recurrence has rarely been noted, and has been reported in less than 2% of cases. Epidermoid cyst (EDC) is a benign cystic lesion, which is lined by stratified squamous epithelium and includes keratin debris. They can present anywhere in the body but are rare in the head and neck areas. In this report, we present an uncommon case of simultaneous occurrence of OOC in mandible and EDC around the areas of both ears in a patient who has no history of genetic syndrome.

Primary intraosseous odontogenic carcinoma (PIOC) is a carcinoma arising within the jaws, putatively developing from remnants of odontogenic epithelium. We describe a case of PIOC arising from odontogenic cyst affecting the left posterior mandible of 72-year-old Korean man. Clinical examination showed a symptom-free hard mass. There was no evidence of ulceration, and there was no pain or bleeding. The overlying mucosa was intact and no regional lymph nodes were palpable. Clinical and radiological studies for other distant primary sites were negative. Radiographically, the tumor showed multilocular radiolucency with a noncorticated, ill defined border surrounding an impacted third molar tooth. Histology exhibited sheets or islands of nonkeratinizing malignant epithelial cells with minimal clear cell component in continuity with begin or dysplastic cyst lining epithelium. Immunostaining for PCNA and p53 protein showed a higher percentage of positive cells and more intense staining in the carcinomatous tissues than in the benign and dysplastic lesions.

The aim of this study was to present the clinical, radiological, and histopathological findings of 20 new Korean GOC cases with a brief literature review. The mean age of 20 GOC patients was 43.5 years (range, 29-73 years) with a strong predilection for male (male-to-female ratio, 4:1). Nine cases were located in the maxilla and 11 cases in the mandible. Eight cases involved the anterior areas of the jaws and 12 cases were located in the posterior area. Most of the cases (16/20, 80.0%) showed a well-defined unilocular radiolucency and some showed cortical perforation (55.6%) and bony expansion (72.2%) in computed tomography. The most common histopathological feature was eosinophilic cuboidal cells (100%), followed by clear cells (95.0%), mucous cells (85.0%), variations in thickness (85.0%), and intraepithelial microcysts (80.0%). All cases were surgically treated by enucleation and no recurrences were found in routine follow-up.

Odontogenic cyst and odontogenic tumor shares developmental source. However, they have different histopathologic features, and they are classified respectively. Odontogenic cyst and tumor can share same physical region. It is called a hybrid lesion, a lesion showing the combined histopathological characteristics of two or more previously recognized odontogenic tumor and/or cysts of different categories. In this study, a hybrid lesion was researched. 61-year old man was referred to our department with a multilocular radiolucency in right mandibular angle. Incisional biopsy was carried out, and the patient was diagnosed with ameloblastoma. Odontogenic keratocyst was found with the tumor, and it was thought to be evolved via neoplastic transformation from lining epithelium of the keratocyst. After reviewing studies reporting hybrid lesions from odontogenic cyst and tumor, formation of a hybrid lesion was most frequent from a dentigerous cyst and an adenomatoid odontogenic tumor. A hybrid lesion commonly lead to misdiagnosis, and the prognosis is not always transparent. The close relationship between the odontogenic cyst and tumor has to be kept in mind in the diagnosis and treatment of the lesions in maxillofacial area.

Although the mechanism of the abnormal calcification in the calcifying odontogenic cyst (COC) was not elucidated so far, it has been known that the ghost cells are closely related to the calcification, producing dystrophic globular cementum-like materials, comparable to pilomatricoma in epithelium1). Here, we presented a case of COC occurred in left maxillary canine area of 23 years old female, exhibiting a collection of aberrant ossification admixed with basophilic ghost cells in comparison with seven cases of COC. In the polarizing microscope observation with Masson trichrome stain the present case clearly disclosed the typical birefringence of bony tissue, stained red in von Gieson stain, indicating the collagenous backbone. Some ghost cells showed the features of interdigitating epithelial attachments, empty spaces of nuclei, and reticular basophilic cytoplasms, which were similar to the basophilic ghost cells of philomatricoma. The present case demonstrated the aberrant ossification by basophilic ghost cells in COC similar to the ossification of pilomatricoma

A dentigerous cyst (DC) and an odontogenc fibroma (OF) in the jaws are well known entities, which have been reviewed extensively. However, the presence of OF components in the wall of dentigerous cyst is a very rare event. A case of DC in the left mandible displaying the foci of an OF-like lesion is described. It is unclear whether the two lesions were just coincidental or were actually related to each other. However, OF-like proliferation may be arised from secondary epithelial and mesenchymal interactions in a pre-existing DC, although the initiating stimulus could not be identified.

A 17-year-old male patient was referred for the extraction of impacted mesiodens and canine (#23) before orthodontic treatment. In the radiologic examination, an ovoid-shape radiolucent lesion was found with well-defined hyperostotic rim involved the teeth in left maxillary area. After biopsy examination the lesion was diagnosed as glandular odontogenic cyst (GOC) differentially from non-odontogrnic cysts, i.e., nasopalatine duct cyst. In the immunohistochemistry the cyst epithelium was freguently positive for PCNA, clearly positive for amtloblastin, slightly positive for β-catenin, but rarely positive for amelogenin and cytokeratin 7. Mucin and PRP were positive in the secretory cells of the cyst epithelium. On the other hand, TNFα was strongly positive in the macropahges infiltrated into the mucin-filled cyst lumen, and CD68 and CD31 were positive in the mucin-filled macropahges. These findings may indicate that the glandular elements are derived from hamartomatous secretory organ and that this odontogenic cyst is arisen from the embryonal rests of enamel epithelium, which has a potential to be differentiated into not only the enamel organ but also the secretory gland. Taken together, we assumed that the present case of GOC was originated from the odontogenic epithelium of impacted teeth, but showed the cytodifferentiation of glandular cells.

This report describes a case of odontogenic cyst with keratinization and dysplastic change of lining epithelium, which showed the manifestation of inflammatory radicular cyst, clinically. A 28-year-old man complained of dull pain in the right mandibular molar region. Radiographically a well-defined oval cystic lesion with non-vital teeth, a common finding in radicular cyst, was observed. Microscopically, the lining epithelium of the cyst demonstrated both keratinization and severe epithelial dysplasia. Atypical findings such as hyperchromatic nuclei, increase of N/C ratio and drop shaped rege ridge were observed in the lining epithelium. However, definite invasion into fibrous connective tissue was not found. Immunohistochemically, the dysplastic lining epithelium was highly positive for proliferative marker, Ki-67. Based on the dysplastic changes of lining epithelium, this periapical lesion would be considered to be signs of malignant change. From this case, we conclude that definitive diagnosis by microscopical examination should be made, even if the periapical lesion would be clinically considered as inflammatory radicular cyst.

A case was reponed in which an odontogenic cyst that appeared to be a dentigerous cyst associated with an impacted mandibular third molar was found histologically to demonstrate characteIistics of glanclu lar odontogenic cyst with para- and orthokeratinization. 까1ese histologic cliversities were interpreted as a reflection of the pluripotentiality of the epithelial remnants of the mandibular thircl molars or clentigerous cyst epithelium. It was conceivable that it would have the capacity of inclucing the fonnation of cysts with both squamous and glandular epithelium.