Developmental Odontogenic Lesions Associated with the Crown of an Impacted Tooth: A Guide to the Distinct Histologic Features Required for Classification

Odontogenic cysts are categorized as inflammatory and developmental. Of the developmental odontogenic cysts, the dentigerous cyst is the most common and by definition is attached to the cervical region of an unerupted tooth. The cyst envelops the crown forming a sac. However, there are other developmental cysts, and rarely, odontogenic tumors, that can have a similar clinical and radiographic presentation as dentigerous cyst, including odontogenic keratocyst, orthokeratinized odontogenic cyst and ameloblastoma, unicystic type. Understanding the key histologic differences of these cysts will aid the pathologist to correctly diagnose these lesions, ensuring appropriate clinical management.     

Evidence of loss of heterozygosity of the PTCH gene in orthokeratinized odontogenic cyst

J Oral Pathol Med (2011) 40 : 277–280 The orthokeratinized odontogenic cyst (OOC) is an odontogenic cyst of unknown etiology. Clinical, histological, and biological differences are reported between keratocystic odontogenic tumor (KOT) and OOC. PTCH is a tumor suppressor gene related to sonic hedgehog (SHH) pathway important in embryological development. Considering that alterations in this pathway have been described in sporadic and nevoid basal cell syndrome‐associated KOT, we tested the hypothesis that OOC is also associated with loss of heterozygosity (LOH) of the PTCH gene. Seven samples of OOC and seven of KOT were included in the study. D9S287, D9S196, and D9S127 microsatellite markers located in the region of PTCH gene, at chromosome 9q, were investigated for LOH. There was loss in at least one locus in 5/7 KOT and in 4/7 OOC samples. The present finding demonstrates that, despite the existence of clinical, morphological, immunohistochemical, and biological behavior differences between OOC and KOT, both harbor similar genetic alterations at 9q.     

Tooth in a cyst — Is it always a dentigerous cyst?

We present the case report of an 18-year-old female patient who presented with unilateral nasal obstruction. Computed tomography scanning revealed an unerupted molar in the posterior wall of the right maxillary sinus with a cystic swelling in the sinus. The preoperative diagnosis was a dentigerous cyst. The patient underwent endoscopic removal of the cyst and tooth. The operative findings and histopathology showed that it was an odontogenic keratocyst. This paper stresses the importance of diagnosing this condition and that a tooth in a cyst is not always dentigerous.     

Discrimination of parakeratinised odontogenic keratocysts from other odontogenic and non-odontogenic cyst types by expression of a 38kd cell-surface glycoprotein

We have identified strong expression of a 38-kD cell surface glycoprotein (gp38), a marker of basal cell carcinomas (BCCs), in basal and suprabasal epithelial cell membranes of parakeratinised odontogenic keratocysts. In contrast, orthokeratinised cysts and most other odontogenic cyst types, ameloblastomas, normal stratified oral epithelium, cell rests of Malassez and glands of Serres, all proved negative. To our knowledge this is the first histochemical marker to distinguish between these major cyst types. It has obvious uses in the diagnosis of inflamed keratocysts and the separation of ameloblastomas from BCCs and may find a role in studies of the developmental biology of other odontogenic structures.     

Human odontogenic keratocyst transplants in nude mice

Abstract – Specimens from human odontogenic keratocysts were subcutaneously transplanted to nude mice. The transplants were harvested after 14–66 d with a rate of successful recovery of 87%. The histologic epithelial features in the original odontogenic keratocyst and their transplants were essentially similar. This included a well-defined basal cell layer composed of columnar and cuboidal cells, the number of cell layers and die keratinization pattern. Epithelial outgrowths from the transplants were found in 19 of 26 cases. The outgrowths over murine connective tissue in the majority of cases were keratinized, but the phenotypic expression differed with respect to the shape of basal cells and number of cell layers.     

A comparative study of epithelial cell proliferation between the odontogenic keratocyst, orthokeratinized odontogenic cyst, dentigerous cyst, and ameloblastoma

OBJECTIVES: The aim of the present study was to compare the proliferation index of the epithelial cells between odontogenic keratocysts (OKC), orthokeratinized odontogenic cysts (OOC), dentigerous cysts (DC), and ameloblastomas. MATERIALS AND METHODS: The proliferation index, employing a novel cell proliferation marker IPO-38, was studied by the immunohistochemical technique in 10 OKC, seven OOC, eight DC and 10 ameloblastomas. RESULTS: The ameloblastoma had no higher labeling index (LI) of IPO-38 than the OKC (P = 0.910) but had higher LI than the OOC (P = 0.001) and DC (P = 0.000); the OKC had higher LI than the OOC (P = 0.002) and DC (P = 0.000); and the OOC had higher LI than the DC (P = 0.011). IPO-38-positive cells in the OKC and OOC were located principally in the suprabasal cell layers while the ameloblastoma were found in the peripheral portion in particularly, the follicular and plexiform types. CONCLUSION: These findings support previous studies that the proliferation indices are useful in predicting the different biological behavior of the odontogenic lesions and the OKC should be regarded as a benign tumor rather than simply an odontogenic cyst.     

牙源性角化囊肿的诊断和治疗

牙源性角化囊肿(OKCs)是一种好发于下颌角及升支部的发育性囊肿。与其他牙源性囊肿相比,OKCs中上皮细胞增殖活性较高、基因片断PTCH突变率高、有丝分裂计数升高,CK16、CK17、CK19等肿瘤标志物高表达。故而,认为OKCs是一良性囊性肿瘤。OKCs的诊断主要依靠影像学、病理学的检查。OKCs的治疗推荐外科的摘除术、周围骨切除术等侵袭性方法,但青年患者OKC病变涉及颌骨及牙的发育时,为了避免侵袭性方法的不良反应,袋形缝合术、减压或冲洗疗法等保守疗法在治疗OKCs中有诸多优点。     

核因子kB受体活化剂配体在牙源性角化囊肿中的表达和意义

目的：明确RANKL在牙源性角化囊肿中的表达和分布,了解牙源性角化囊肿骨破坏的机制。方法：经病理诊断的牙源性角化囊肿组织切片,用免疫组化法检测RANKL的表达及分布,用TRAP的免疫组化和降钙素受体的原位杂交明确RANKL阳性细胞的性质。结果：所有标本均显示RANKL阳性,阳性细胞位于牙源性角化囊肿的上皮层;均显示TRAP阳性,阳性细胞位于牙源性角化囊肿的上皮层,两种指标的阳性细胞定位类似;均显示CTR阳性,阳性细胞位于囊肿的上皮层,与RANKL和TRAP的阳性细胞定位类似。结论：RANKL在牙源性角化囊肿引起的颌骨破坏中起作用。