Ghost cells in complex odontoma: a light microscopic and SEM study

A spontaneous compound odontoma in an adult Sprague Dawley rat (Rattus norvegicus)

Reports of compound odontomas in rats are very rare. A 14-month-old adult male Sprague Dawley rat was found to have a hard mass associated with the caudal aspect of the left mandible. After 2 weeks of observation, the rat was euthanized due to the mass growing significantly in size and the rat losing >20% of its body weight. Grossly, the mass was well-circumscribed, 3.7 × 3 × 1.2 cm, hard and heterogeneously coloured white, tan and red. The mass was restricted to the mandibular bone and did not involve surrounding subcutaneous tissue. On cut surface, the mass was a similar colour and brittle. Histologically, there were numerous proto-teeth embedded in ossified stroma. Each proto-tooth had a central mesenchyme pulp surrounded by columnar odontoblasts and dentine matrix. The dentine was often bordered by enamel matrix, which was occasionally bounded by ameloblasts. These histological findings were consistent with a compound odontoma. This is the first report of a spontaneous compound odontoma in the caudal mandible of a rat.

Ghost cells unveiled: A comprehensive review

BACKGROUND

Ghost cells (GCs) are cells with distinct intracytoplasmic keratinization, which leads to the preservation of the cellular outline with a clear area corresponding to the previous nucleus location. GCs may show various patterns, such as degeneration, tissue granulation, and calcification. Their true nature and the mechanism regulating the conversion of odontogenic epithelial cells into GCs remain unclear. GC keratinization is different from normal keratinization as they are larger than keratotic squames, are frequently vacuolated, and have prominent nuclear membrane remnants. Few cystic lesions, odontogenic tumors, and non-odontogenic tumors, such as calcifying odontogenic cyst, craniopharyngioma, pilomatrixoma, odontoma, dentinogenic ghost cell tumor, and ghost cell odontogenic carcinoma, exhibit GCs as a typical feature. The Wnt and Notch signaling pathways play a role in the histogenesis of the neoplasms.

HIGHLIGHT

The review clarifies the various proposed hypotheses of the histogenesis of GCs, including molecular pathogenesis. Diagnostic workup for the identification of GCs, including special staining and immunohistochemistry, has been extensively discussed. A stepwise algorithm for identifying odontogenic and non-odontogenic lesions containing GCs has been proposed. Additionally, the prognostic role of GCs in the lesions has been elucidated.

CONCLUSION

Among the various hypotheses of the origin of GCs, we suggest that aberrant keratinization is the most accepted based on various immunohistochemical studies and special staining characteristics. GCs are a distinct characteristic entity of many odontogenic and non-odontogenic lesions; however, it remains controversial whether their presence has any pathognomonic role in the biological nature of these lesions.

A Contemporary Approach to Classify Ghost Cells Comprising Oral Lesions

Ghost cells are swollen eosinophilic epithelial cells that have lost their nuclei but retain the cellular and nuclear outline. Pathologic ghost cell formation could be the process of aberrant keratinization or the result of coagulative necrosis. Ghost cells have been described in several odontogenic lesions, which include calcifying epithelial odontogenic cysts or tumours like odontomas, ameloblastic fibro-odontomas, and ameloblastomas. This article present a view on the formation of ghost cells with proposal/introduction of a classification for ghost cell lesions of the oral cavity in an attempt to organize these lesions for the better understanding and academic purpose.

Ghost cell lesions

Ghost cells have been a controversy for a long time. Ghost cell is a swollen/enlarged epithelial cell with eosnophilic cytoplasm, but without a nucleus. In routine H and E staining these cells give a shadowy appearance. Hence these cells are also called as shadow cells or translucent cells. The appearance of these cells varies from lesion to lesion involving odontogenic and nonodontogenic lesions. This article review about the origin, nature and significance of ghost cells in different neoplasms.

Ghost cells in pilomatrixoma, craniopharyngioma, and calcifying cystic odontogenic tumor: histological, immunohistochemical, and ultrastructural study

BACKGROUND

Pilomatrixoma, craniopharyngioma, and calcifying cystic odontogenic tumor are the main entities presenting ghost cells as an important histological feature, in spite their quite different clinical presentation; it seems that they share a common pathway in the formation of these cells. The aim of this study is to examine and compare the characteristics of ghost and other cells that form these lesions.

METHODS

Forty-three cases including 21 pilomatrixomas, 14 craniopharyngiomas, and eight calcifying cystic odontogenic tumors were evaluated by immunohistochemistry for cytokeratins, CD138, β-catenin, D2-40, Glut-1, FAS, CD10 and also by scanning electron microscopy.

RESULTS

The CKs, CD138, β-catenin, Glut-1, FAS, and CD10 were more often expressed by transitional cells of craniopharyngioma and calcifying cystic odontogenic tumor, compared with pilomatrixoma. Basaloid cells of pilomatrixoma showed strong positivity for CD138 and CD10. Differences on expression pattern were identified in transitional and basal cells, as ghost cells were negative for most antibodies used, except by low expression for cytokeratins. By scanning electron microscopy, the morphology of ghost cells were similar in their fibrillar cytoplasm, but their pattern varied from sheets in pilomatrixoma to small clusters in craniopharyngioma and calcifying cystic odontogenic tumor.

CONCLUSIONS

Mechanisms involved in formation of ghost cells are unknown, but probably they follow different pathways as protein expression in the basal/transitional cells was not uniform in the three tumors studied.

Notch signaling and ghost cell fate in the calcifying cystic odontogenic tumor

Notch signaling is an evolutionarily conserved mechanism that enables adjacent cells to adopt different fates. Ghost cells (GCs) are anucleate cells with homogeneous pale eosinophilic cytoplasm and very pale to clear central areas (previous nucleus sites). Although GCs are present in a variety of odontogenic lesions notably the calcifying cystic odontogenic tumor (GCOT), their nature and process of formation remains elusive. The aim of this study was to investigate the role of Notch signaling in the cell fate specification of GCs in CCOT. Immunohistochemical staining for four Notch receptors (Notch1, Notch2, Notch3 and Notch4) and three ligands (Jagged1, Jagged2 and Delta1) was performed on archival tissues of five CCOT cases. Level of positivity was quantified as negative (0), mild (+), moderate (2+) and strong (3+). Results revealed that GCs demonstrated overexpression for Notch1 and Jagged1 suggesting that Notch1Jagged1 signaling might serve as the main transduction mechanism in cell fate decision for GCs in CCOT. Protein localizations were largely membranous and/or cytoplasmic. Mineralized GCs also stained positive implicating that the calcification process might be associated with upregulation of these molecules. The other Notch receptors and ligands were weak to absent in GCs and tumoral epithelium. Stromal endothelium and fibroblasts were stained variably positive.

Peripheral dentinogenic ghost cell tumor: report of a case and literature review

Peripheral dentinogenic ghost cell tumor is a rare tumor with only 24 cases previously described in the English literature. The majority of cases have been reported to occur in the anterior part of the jaws. A case occurring in posterior (molar region) of the mandible in a 75-year-old edentulous woman is reported. The patient presented with a nodular swelling in the left mandible that showed erosion (saucerization) of the underlying bone radiographically. On microscopy, the tumor showed mainly solid epithelial islands resembling ameloblastoma in fibrous connective tissue. The islands were associated with ghost cells and dysplastic dentin. This report includes the clinical, radiographic, and microscopic features of the patient, in addition to the review of the English literature on the tumor.

Podoplanin expression in odontomas: clinicopathological study and immunohistochemical analysis of 86 cases

Podoplanin, a sialomucin-like transmembrane glycoprotein, is currently used as a specific marker for lymphatic vessels. However, podoplanin expression has also been linked to tooth development. To investigate the expression of podoplanin in odontomas, 86 tissue samples were classified and then analyzed using immunohistochemical methods. Formalin-fixed, paraffin-embedded specimens were collected and classified, followed by immunohistochemical examination. The majority of the odontomas (66.3%) were the compound type, and the remainder (33.7%) were the complex type. The patients ranged in age from 2 to 89 years (mean, 23.9 years), and 45 (52.3%) of them were male and 41 (47.7%) were female. The most common location for complex odontomas was the molar region of the mandibular bone, and that for compound odontomas was the maxillary incisor region. Immunohistochemistry revealed that developing and mature odontoblasts, Tomes' fibers, and pulp cells near podoplanin-positive odontoblasts were positive for podoplanin. In addition, podoplanin positivity was evident in secretory ameloblasts, but not in mature ameloblasts. The pattern of podoplanin expression in odontomas corresponds to development of the tooth germ, and appears to be influenced by the stage of differentiation of the lesion, suggesting that the protein may participate in the process of differentiation.

Immunoexpression of keratins in the calcifying cystic odontogenic tumor epithelium

Ameloblastomatous epithelium containing clusters of ghost cells is the typical histopathology of calcifying cystic odontogenic tumor (CCOT). This paper aimed to assess keratins AE1-AE3, K7, K10/13, K14, K18, K19, vimentin, laminin, and collagen IV in 08 CCOTs to discuss their histopathogenesis. Similarity to the immunoprofile of the stratified squamous epithelium was seen in the with the basal layer expressing K14 and the upper cells expressing K10/13. When compared to the immunoprofile of the normal odontogenic epithelium, of odontogenic tumor epithelia and of the ghost cells described in the literature, it was possible to suggest that the CCOT epithelium differentiates towards squamous type.

A pigmented calcifying cystic odontogenic tumor associated with compound odontoma: a case report and review of literature

Background

Pigmented intraosseous odontogenic lesions are rare with only 47 reported cases in the English literature. Among them, pigmented calcifying cystic odontogenic tumor, formerly known as calcifying odontogenic cyst, is the most common lesion with 20 reported cases.

Methods

A case of pigmented calcifying cystic odontogenic tumor associated with odontoma occurring at the mandibular canine-premolar region of a young Japanese boy is presented with radiographic, and histological findings. Special staining, electron microscopic study and immunohistochemical staining were also done to characterize the pigmentation.

Results

The pigments in the lesion were confirmed to be melanin by Masson-Fontana staining and by transmission electron microscopy. The presence of dendritic melanocytes within the lesion was also demonstrated by S-100 immunostaining.

Conclusion

The present case report of pigmented calcifying cystic odontogenic tumor associated with odontoma features a comprehensive study on melanin and melanocytes, including histochemical, immunohistochemical and transmission electron microscopic findings.

Ghost cells in calcifying odontogenic cyst express enamel-related proteins

The so-called ghost cell is a unique cell type occurring in a variety of odontogenic and non-odontogenic lesions. However, the true nature of ghost cells has not been determined. In the present study, we examined the immunoreactivity of ghost cells in calcifying odontogenic cysts and dermal calcifying epitheliomas, with antibodies against amelogenin, enamelin, sheath protein (sheathlin) and enamelysin, in an attempt to clarify the nature of this unique cell. The cytoplasm of ghost cells in calcifying odontogenic cysts demonstrated distinct immunolocalization of the enamel-related proteins, while similar in the calcifying epitheliomas of the skin showed a negative reaction. The results indicate that the ghost cells in calcifying odontogenic cysts, as opposed to ghost cells in dermal calcifying epitheliomas, contain enamel-related proteins in their cytoplasm accumulated during the process of pathological transformation.

Gingival compound odontoma

Peripheral odontomas arising in gingival tissue are very rare; only three have been reported to date. The case of a peripheral odontoma arising in the gingiva of a 3-year-old girl is presented.

Calcifying odontogenic cyst. A review of ninety-two cases with reevaluation of their nature as cysts or neoplasms, the nature of ghost cells, and subclassification

Ninety-two cases of calcifying odontogenic cyst (COC) were reviewed with special consideration of their nature as cysts or neoplasms, the nature of ghost cells, and classification on the basis of clinicopathologic features. The cases were divided into 79 (85.9%) cysts and 13 (14.1%) neoplasms. The cysts occurred as four variants: (1) nonproliferative COC (35 cases), characterized by a simple unicystic structure; (2) proliferative COC (17 cases), characterized by a cystic structure with multiple daughter cysts, extensive ghost cell formations, and marked tendency for calcification; (3) ameloblastomatous COC (11 cases), characterized by ameloblastoma-like, cyst-lining epithelium with ghost cells and calcifications; and (4) COC associated with odontoma (16 cases), which combined features of COC and odontoma. The neoplasms occurred as three variants: (1) ameloblastoma ex COC (two cases), which showed unifocal and multifocal intraluminal and intramural ameloblastoma proliferating from the COC-lining epithelium; (2) peripheral epithelial odontogenic ghost cell tumor (eight cases), which occurred in the gingiva and resembled peripheral ameloblastoma except for clustered ghost cells in the central portion of epithelial islands and the presence of juxtaepithelial dentinoid; and (3) central epithelial odontogenic ghost cell tumor (three cases). The latter showed ameloblastomatous or adenomatoid odontogenic tumor-like epithelial clusters with ghost cell formation and juxtaepithelial dentinoid. The clinical features of cystic and neoplastic variants were tabulated and described. On the basis of histopathologic features and their immunohistochemical reaction to polyclonal antikeratin antibody, it is suggested that ghost cells might be the result of coagulative necrosis.

Calcifying odontogenic cyst immunohistochemical detection of keratin and involucrin in cyst wall

Calcifying odontogenic cysts (COC) were immunohistochemically described using different keratin proteins and involucrin as well as histopathology. The cystic lining epithelium was composed of calcifying, keratinizing, squamous, and columnar epithelial cells, and included calcified masses of irregular shape and various size as well as ghost cells. Calcifying epithelium gave negative or only trace staining for keratins detected with low molecular keratin (PKK1), but were regularly positive with high molecular keratin (KL1) and polyclonal antibody for keratin (TK). They were occasionally positive for involucrin. The cells located in the periphery of the calcified masses had a particular abundance of high molecular weight and total keratins (KL1 and TK). Calcified bodies and ghost cells were devoid of any immunoreactivity. Squamous epithelium was relatively similar to that of normal squamous cell epithelium in the oral mucosa. It were most commonly found in columnar cystic epithelial cells which displayed intense staining with all immunoreagents. It is postulated that such epithelial cells may have a strong potentiality to transform into ghost cells or to undergo metaplasia. They may develop altered synthesis of homogenous acellular materials and finally become transformed into calcifying epithelium containing dystrophic calcified masses.