Benign and malignant odontogenic neoplasms of the jaws show a concordant nondiscriminatory p63/p40 positive immunophenotype.

OBJECTIVES: Antibody p40, which recognizes exclusively ΔNp63 but not TAp63, has shown diagnostic utility in salivary gland and sinonasal tract malignancies. Although p63 immunophenotypic characterization of odontogenic lesions has been reported, p40 expression has not been previously studied. We aimed to study p40 immunoreactivity in odontogenic tumors (OTs) and odontogenic cysts (OCs) and to investigate possible discriminatory properties of the combined p63/p40 immunoprofile in OTs and OCs. STUDY DESIGN: Fourteen ameloblastomas, 7 adenomatoid odontogenic tumors, 6 calcifying epithelial odontogenic tumors, 1 squamous odontogenic tumor, 4 primary intraosseous odontogenic carcinomas, 5 calcifying odontogenic cysts, 4 glandular odontogenic cysts, 3 odontogenic keratocysts, 3 dentigerous cysts, and 1 each radicular and orthokeratinized cysts were stained for p63 (4A4) and p40 (BC28) antibodies. RESULTS: Ameloblastoma, adenomatoid odontogenic tumor, calcifying epithelial odontogenic tumor, squamous odontogenic tumor, and primary intraosseous odontogenic carcinoma demonstrated concordant p63+/p40+ immunophenotype. P40, similar to p63, highlighted almost all lesional cells of OTs and, overall, the full thickness of the epithelial lining of the cystic areas of OCs and ameloblastoma. The keratin layer of OKC and the adluminal ductal and mucous cells of GOC were p63-/p40-. CONCLUSIONS: Both ΔNp63 and TAp63 isoforms are present in neoplastic and developmental odontogenic lesions; and p63/p40 immunophenotype is nondiscriminatory pertaining to benign and malignant OTs and OCs.

Immunoexpression of proteins involved in cytoskeleton remodeling in benign odontogenic lesions.

OBJECTIVE: The present study was designed to analyze the immunolocalization of proteins involved in cytoskeleton remodeling, such as moesin and Rho-A, in benign odontogenic lesions that present with expansive growth and invasive clinical behavior. MATERIALS AND METHODS: Expressions of moesin and Rho-A in odontogenic epithelium were evaluated by immunohistochemical analysis in 45 odontogenic lesions using monoclonal antibodies. RESULTS: Our results demonstrated strong membranous and cytoplasmic expressions of moesin in the epithelial cells in 66.7% and 44.4% of the odontogenic lesions, respectively. Furthermore, Rho-A expression in odontogenic epithelium was strong in the membrane and cytoplasm of 51.1% and 62.2% of the odontogenic lesions, respectively. A statistically significant correlation was found between the membranous and cytoplasmic expressions of moesin (p = 0.000) and those of Rho-A (p = 0.048) in odontogenic epithelial cells, while no statistically significant correlation was found between moesin and Rho-A expressions (p > 0.05). CONCLUSIONS: The present study confirmed the strong expressions of moesin and Rho-A by odontogenic epithelial cells, suggesting their involvement in the development of benign odontogenic lesions. However, this study has failed to detect the connection between the moesin and Rho-A interaction in expansive growth and local invasiveness of these lesions.

Primordial odontogenic tumor: An immunohistochemical profile.

BACKGROUND: Primordial Odontogenic Tumor (POT) is a recently described odontogenic tumor characterized by a variably cellular loose fibrous tissue with areas similar to the dental papilla, covered by cuboidal to columnar epithelium that resembles the internal epithelium of the enamel organ, surrounded at least partly by a delicate fibrous capsule. The purpose of this study was to investigate the possible histogenesis and biological behavior of this rare tumor by means of a wide immunohistochemical analysis of its epithelial and mesenchymal components. MATERIAL AND METHODS: The immunoexpression of twenty-three different antibodies were evaluated in four cases of POT. RESULTS: The epithelial cells that cover the periphery of the tumor showed immunopositivity for Cytokeratins 14 and 19, while Amelogenin, Glut-1, MOC-31, Caveolin-1. Galectin-3, PITX2, p53, Bax, Bcl-2, Survivin and PTEN were variably expressed in focal areas. The mesenchymal component of the tumor was positive for Vimentin, Syndecan-1, PITX2, Endoglin (CD105), CD 34, Cyclin D1, Bax, Bcl-2, Survivin and p53. PTEN and CD 90 showed a moderate positivity. BRAF V600E and Calretinin were negative in all samples. Cell proliferation markers (Ki-67, MCM-7) were expressed in <5% of the tumor cells. CONCLUSIONS: According to these immunohistochemical findings, we may conclude that POT is a benign odontogenic tumor in which there is both epithelial and mesenchymal activity during its histogenesis, as there is expression of certain components in particular zones in both tissues that suggests this tumor develops during the immature (primordial) stage of tooth development, leading to its inclusion within the group of benign mixed epithelial and mesenchymal odontogenic tumours in the current World Health Organization classification of these lesions.

Immunoexpression of tumour necrosis factor-α, interleukin-1α and interleukin-10 on odontogenic cysts and tumours.

AIM: To analyse the immunoreactivity of IL-1α, TNF-α and IL-10 in odontogenic cysts and tumours and to investigate possible associations with established biological behaviours of these different lesions. METHODOLOGY: Immunohistochemical expression of anti-IL-1α, anti-TNF-α and anti-IL-10 antibodies was assessed on epithelium and mesenchyme of 20 radicular cysts (RCs), 20 residual cysts (RECs), 20 dentigerous cysts (DCs), 18 solid ameloblastomas (SAs), 20 keratocystic odontogenic tumours (KCOTs) and 15 dental follicles (DFs). Comparative analysis of data was performed using the nonparametric Wilcoxon signed-rank test and Kruskal-Wallis's test. RESULTS: Significantly greater expression of IL-1α in the epithelium was noted in RC, KCOT and SA (P = 0.01), whilst IL-10 and TNF-α was in the epithelium of RC, DC and KCOT (P < 0.01). In the mesenchyme, significantly greater immunopositivity was observed for IL-1α, IL-10 and TNF-α in KCOT, DC and RC (P < 0.01). In epithelial and mesenchymal tissues, there were a significant number of cases of RC and DC with IL-1α < IL-10 ratio (P < 0.01), whilst SA and KCOT showed IL-1α > IL-10 (P < 0.01). There was a significantly greater percentage of DF, DC and KCOT with TNF-α > IL10 ratio (P < 0.01). CONCLUSION: These results suggest involvement of the proteins in the pathogenesis of odontogenic cysts and tumours, with emphasis on the highest immunoreactivity of osteolysis stimulating factors in tumours with aggressive biological behaviour, such as SA and KCOT.

IMMUNOEXPRESSION OF TWIST IN DIFFERENT MORPHOLOGICAL VARIANTS OF AMELOBLASTOMAS.

BACKGROUND: Ameloblastoma is the most common and a clinically significant odontogenic tumour. The diagnosis and sub classification of ameloblastoma have been traditionally relied on histological assessment, but it is still a subject of debate. The aim of this study was to evaluate the immuno-expression of Twist in various subtypes of ameloblastomas and their corelation with various histological variants. METHODS: This cross-sectional study was conducted in the Department of Pathology, Post Graduate Medical Institute, Lahore between June to December 2013. Thirty cases of various types of Ameloblastomas were included in this study. Histological sub-classification of the tumours was performed based on WHO classification. Twist expression of these tumours was estimated by immunohistochemistry, performed on paraffin sections. RESULTS: Out of these thirty cases, 22 (73%) were newly diagnosed typical solid/multicystic intraosseous ameloblastoma, 2 (7%) cases belonged to recurrent ameloblastoma, and 3 (10%) each were diagnosed as peripheral/extraosseous ameloblastoma and ameloblastic carcinoma. On histopathological sub-classification of the newly diagnosed solid ameloblastoma, 8 cases were diagnosed as follicular ameloblastoma in which 3 cases (37.5%) were negatively stained, 4 cases (50%) were mild positive and 1 case (12.5%) was moderate positive with Twist immunostaining. Out of 5 cases of plexiform ameloblastoma 3 cases (60%) were mild positive. Out of 4 cases of acanthomatous ameloblastoma 2 (50%) were moderate positive and 2 cases (50%) were strong positive. All granular cell ameloblastoma stained positive. The only case of desmoplastic ameloblastoma was moderately positive. Both the cases of recurrent ameloblastoma were strongly positive. All 3 cases of peripheral ameloblastoma stained negatively. All ameloblastic carcinoma were strongly positive. CONCLUSION: Twist immunohistochemical analysis can be used as an adjuvant to H&E histopathological findings for proper categorization and grading of ameloblastoma especially in the clinically aggressive tumours.

Differential expression of TLR3 and TLR4 in keratocystic odontogenic tumor (KCOT): A comparative immunohistochemical study in primary, recurrent, and nevoid basal cell carcinoma syndrome (NBCCS)--associated lesions.

BACKGROUND: Toll-like receptors (TLRs) play an essential role in the activation of innate immunity and they can promote cancer cell survival and tumor progression. It has been claimed that TLRs can somehow predict the clinical behavior in oral squamous cell carcinoma (OSCCs). AIM: To elucidate the molecular basis underlying keratocystic odontogenic tumor (KOCTs) aggressive behavior and recurrence we carried out this immunohistochemical study on TLR3 and TLR4 expression in sporadic primary KCOTs (sp-KCOTs), sporadic recurrent KCOTs (sp-KCOTs), and NBCCS-associated KCOTs (NBCCS-KCOTs). METHOD: 40 cases of KOCTs removed from 23 men and 17 women were the sample. Paraffin-embedded blocks were processed for immunohistochemistry. Sections were incubated with TLR3 and TLR4 antibodies and immunoreactivity evaluated on a semi-quantitative score. RESULTS: Both TLR3 and TLR4 were expressed in KCOTs epithelium, although with a different extent. TLR3 was not expressed in sp-KCOTs and sr-KCOTs, but it showed a faint staining in NBCCS-KCOTs. On the other hand, both cytoplasmic and nuclear staining for TLR4 was detected in all the 3 types of lesions; however being significantly more expressed in sr-KCOT and NBCCS-KCOTs (p < 0.0001). Our results, demonstrated an association between TLR4, but not TLR3 expression to recurrence behavior of KCOTs. In fact, TLR4 was up-regulated in sr-KCOTs and NBCCS-KCOTs but not in sp-KCOTs. CONCLUSIONS: According these findings it seems conceivable to assume that the up-regulation of TLR4 in some KCOTs can be correlated somehow to their tendency recurrence.

FDG-PET/CT in staging of clear cell odontogenic carcinoma.

Clear cell odontogenic carcinoma (CCOC) is a rare neoplasm; only 75 cases have been reported in the English language literature. They have a tendency for recurrence and a capacity to metastasize. There is very little known regarding the metabolic features of this tumour or the utility of fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) scans in the staging and follow-up of these tumours. We present two cases of CCOC with their relevant FDG-PET/CT scan findings. The first patient had primary CCOC of the mandible that was FDG-avid, and the other had recurrence of CCOC of the anterior mandible and superomedial orbit that was not FDG-avid. FDG uptake in CCOC appears to be variable. Although FDG-PET/CT is useful in other head and neck cancers and has benefits compared to other imaging modalities, further studies are needed to investigate the sensitivity of FDG-PET/CT in CCOC.

Does cytokine profiling of aspirate from jaw cysts and tumors have a role in diagnosis?

PURPOSE: The objective of the present study was twofold: first, to assess aspirates for use in cytokine profiling and second, to initiate pilot analyses to determine whether the cytokine profiling can serve as an aid in the diagnosis of jaw lesions. MATERIALS AND METHODS: The aspirates from 12 benign odontogenic cysts and tumors of the jaw were collected and randomized, and a formal incisional biopsy was performed to establish the tissue diagnosis. The biopsies revealed keratocystic odontogenic tumor, ameloblastoma, and dentigerous cyst. The cystic aspirate was analyzed using the Q-Plex Human Cytokine Screen to detect cytokine expression and determine the level of expression for each pathologic entity. An array of 16 cytokines was investigated, including interleukin (IL)-1α, IL-1ß, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12, IL-13, IL-15, IL-17, IL-23, interferon-γ, tumor necrosis factor (TNF)-α, and TNF-ß. Tables were developed to determine the ratio of expression for the candidate cytokine pairs that were differentially expressed among the 3 pathologic entities encountered. One-way analysis of variance was used to search for significant differences in the ratio of expression of the candidate pairs among the 3 entities. RESULTS: Cytokines expressed by the 3 distinct jaw lesions were detected in the aspirate without the need for tissue biopsy. Cytokine profiling of these entities is possible owing to differential expression of the various cytokines studied. The ratio of expression was significant (P < .05) for 15 pairs of cytokines: IL-5/IL-1α, IL-4/IL-2, IL-8/IL-4, TNF-ß/IL-6, IL-23/IL-6, TNF-α/IL-23, TNF-α/TNF-ß, TNF-α/IL-8, TNF-ß/IL-5, TNF-ß/TNF-α, TNF-ß/IL-13, IL-12/IL-23, IL-13/IL-15, IL-15/IL-2, and IL-6/IL-2. A comparison of the mean values indicated a "high/low" expression value for each lesion type for the 15 cytokine pairs. CONCLUSIONS: Cytokines, expressed by the 3 groups of jaw lesions, can be detected in the cystic aspirate, and a comparison of the ratio of the expression of the aspirates demonstrated a differential expression pattern of cytokines among the 3 groups. These ratios could assist in establishing a prompt and accurate diagnosis of lesions that might be difficult to discern clinically and radiographically. The use of a simple, minimally invasive aspiration procedure can help to establish an accurate diagnosis.

Imunolocalização da podoplanina em tumores odontogênicos benignos / Immunolocalization of the podoplanin in benign odontogenic tumours

A podoplanina humana é uma glicoproteína que se expressa em várias células e tecidos normais e neoplásicos, inclusive aqueles de origem odontogênica. O objetivo deste estudo foi identificar a imunolocalização da podoplanina em tumores odontogênicos epiteliais com e sem ectomesênquima incluindo oito ameloblastomas, nove tumores odontogênicos adenomatóides, vinte tumores odontogênicos queratocísticos, cinco cistos odontogênicos ortoqueratinizados, um tumor odontogênico epitelial calcificante, dois fibromas ameloblásticos, quatro fibroodontomas ameloblásticos e cinco tumores odontogênicos císticos calcificantes. Todos os tumores odontogênicos foram submetidos a imuno-histoquímica para o anticorpo anti-podoplanina numa diluição de 1:100 e avaliados, microscopicamente, com base na distribuição tecidual e na intensidade da imunomarcação. Para os tumores odontogênicos queratocísticos e cistos odontogênicos ortoqueratinizados além da podoplanina foi determinado o índice de proliferação celular baseado na positividade nuclear das células do epitélio odontogênico imunomarcadas com o Ki-67 na diluição de 1:200 e comparados estatisticamente pelo coeficiente de correlação de Spearman. Os resultados mostraram uma forte expressão da podoplanina na membrana e no citoplasma do epitélio odontogênico da maioria dos tumores analisados, bem como, em células ectomesênquimais como os odontoblastos e suas extensões dentinárias. A ausência da podoplanina foi identificada nos ameloblastos completamente diferenciados, nas áreas de metaplasia escamosa, nas células fantasmas, nas áreas de calcificação e nos depósitos extracelulares de material eosinofílicos observados nos tumores odontogênicos. No tumor odontogênico queratocístico observou-se uma forte expressão da podoplanina na camada basal e suprabasal do epitélio, enquanto que, nos cistos odontogênicos ortoqueratinizados esta expressão estava ausente ou fracamente distribuída no epitélio. Houve uma correlação estatisticamente...

Human podoplanin is a glycoprotein expressed in various cells and normal and neoplastic tissues, including those of odontogenic origin. The aim of this study was to identify the immunolocalization of podoplanin in epithelial odontogenic tumors with and without ectomesenchyme, including eight ameloblastomas, nine adenomatoid odontogenic tumors, twenty keratocystic odontogenic tumors, five orthokeratinized odontogenic cysts, one calcifying epithelial odontogenic tumor, two ameloblastic fibromas, four ameloblastic fibro-odontomas and five calcifying cystic odontogenic tumors. All odontogenic tumors were submitted to immunohistochemistry using a podoplanin antibody at a dilution of 1:100 and evaluated microscopically, based on the tissue distribution and intensity of immunoreactivity. For keratocystic odontogenic tumors and orthokeratinized odontogenic cysts, in addition to podoplanin, the index of cell proliferation was determined based on the nuclear positivity of odontogenic epithelial cells immunostained with Ki-67 at a dilution of 1:200 and statistically compared by the Spearman correlation coefficient. The results showed strong expression of podoplanin in the membrane and cytoplasm of the odontogenic epithelium of most tumors analyzed, as well as in ectomesenchymal cells as odontoblasts and dentinal projections. Absence of podoplanin was observed in fully differentiated ameloblasts, in areas of squamous metaplasia, in ghost cells, in areas of calcification and extracellular deposits of eosinophilic material observed in odontogenic tumors. The keratocystic odontogenic tumor exhibited strong expression of podoplanin in basal and suprabasal epithelial layers, while in orthokeratinized odontogenic cysts this expression was absent or weakly distributed in the epithelium. There was statistically significant correlation (p=0,006) between the expression of podoplanin and the cellular proliferation index of odontogenic tumors and orthokeratinized odontogenic cysts...

Immunolocalisation of laminin-1 in keratocystic odontogenic tumors.

Keratocystic odontogenic tumors (KOTs) are distinct odontogenic lesions frequently affecting the jawbones. They may be associated with nevoid basal cell carcinoma syndrome (NBCCS), and may exhibit disorders involving the extracellular matrix. The aim of this study was to investigate the immunolocalisation of laminin-1 in 20 cases of KOTs in order to contribute to the characterization of this protein, which is little studied in odontogenic tumors. Our results showed laminin-1 in all 20 KOTs studied; its labelling intensity was weak in three cases (15%), moderate in five (25%) and strong in 12 cases (60%). Laminin-1 immunolocalisation was predominantly continuous in 18 (90%) KOTs, including areas of acanthosis, subepithelial split and epithelial buds. Weak immunolabelling was observed in regions exhibiting an inflammatory process, especially in the case of intense inflammation. These findings suggest that laminin-1 does not participate in biological processes such as cystic epithelium-cystic wall separation or the formation of epithelial islands in KOTs. Furthermore, the discontinuous and weak labelling of this protein in the basement membrane of these tumors is probably a consequence of the inflammatory process in the tumor stroma.

Immunohistochemical features of proliferative marker and basement membrane components of two feline inductive odontogenic tumours.

Feline inductive odontogenic tumour (FIOT) is a rare and interesting odontogenic neoplasm in which the odontogenic epithelium has inductive potential to form aggregated foci of dental pulp-like mesenchymal cells. Two male cats aged 11 and 10 months presented with nasal swelling and a left maxillary mass. Histopathologically, the masses consisted of non-encapsulated invasive neoplasms exhibiting proliferation of epithelial and mesenchymal components with local infiltration into the maxillary bone in both cases. The epithelial component formed islands, anastomosing strands, and solid sheets of polygonal epithelial cells. Occasionally, these cells formed circular aggregates, resembling the cap stage of odontogenesis. Type IV collagen and laminin were constantly positive around the foci of epithelial cells, and Ki-67 positive indices were extremely low; therefore, these findings consistent with the benign clinical presentation of FIOT.

CD34 expressing ameloblastic fibrosarcoma arising in the maxilla: a new finding.

Ameloblastic fibrosarcoma (AFS) is a rare malignant tumor of the jaw. The malignant mesenchymal component of AFS has been described as 'fibroblast-like', although little is known about the immunophenotype, except for vimentin expression. Here, we present a case of AFS in a 62-year-old woman. The mesenchymal component displayed the features of either dermatofibrosarcoma protuberans or fibrosarcoma, and was positive for CD34. This is the first reported case of CD34 expressing AFS in the maxilla.

Expressão imuno-histoquímica das integrinas a2B1, a5B1 em ameloblastoma, tumor odontogênico adenomatoide e germes dentais humanos / Imuno-histochimic expression of the integrinas a2B1, a3B1, and a5B1 ameloblastomatic, adenomatoid odontogenic tumor and human dental embryos

O objetivo deste estudo foi analisar a expressão das integrinas a2B1, a3B1 e a5B1 em ameloblastomas, tumores odontogênicos adenomatóides (TOAs) e germes dentais fetais através da técnica imuno-histoquímica, visando verificar possíveis diferenças na expressão destas integrinas entre as lesões estudadas e entre estas e os germes dentais. Foram selecionados 30 ameloblastomas (20 sólidos e 10 unicísticos), 12 TOAs e 5 germes dentais em diferentes fases da odontogênese. Foram avaliadas a distribuição, localização, padrão e intensidade da expressão imuno-histoquímica. Na análise da intensidade estabeleceu-se escores de 0 a 2, onde 0 corresponde a ausência de marcação, 1 marcação fraca e 2 marcação forte. Comparando-se os ameloblastomas sólidos e os unicísticos não se observou diferença estatisticamente significativa na expressão das integrinas estudadas (teste de Mann-Whitney, p maior que 0,05). Quando os dois tipos clínicos-patológicos de ameloblasotmas foram reunidos em um único grupo, a intensidade de marcação das integrinas diferiu significativamente (Teste de Kruskal-Wallis com pós-teste de Dunn, p menor que 0,05). Para a integrina a2B1 a marcação foi significativamente mais forte em ameloblastomas do que nos TOAs e germes dentais; para a integrina a3B1 a marcação foi significativamente mais forte em ameloblastomas e TOAs quando comparados dois germes dentais e, para a integrina a5B1 a marcação foi mais forte nos ameloblastomas do que nos TOAs. Conclui-se que as variações na expressão imuno-histoquímica das integrinas a2B1, a3B1 e a5B1 nos ameloblastomas, tumores odontogênicos adenomatóides e nos germes dentais estudados, sugerem uma possível influência destas integrinas nos eventos celulares e nas interações célula-matriz nestas neoplasias e na odontogênese

Epidermal growth factor receptor in odontogenic cysts and tumors.

The expression of epidermal growth factor receptor (EGFR) was investigated in 67 cases of odontogenic cysts and 35 cases of odontogenic tumors using monoclonal antibody to EGFR (Biomarker, Israel) to determine the presence and significance of this transmembrane growth factor receptor. The cystic epithelial cells of odontogenic cystic lesions (keratocyst 60%; primordial cyst 75%; radicular cyst 35%; and follicular cyst 47.4%) were positive to EGFR staining. Cytochemical characterization of EGFR in those cystic epithelium was cell membrane positive type as in the normal epithelium. No expression of EGFR was found in the odontogenic tumors. This diversity of EGFR represents no binding activity of EGF, or loss of EGFR in the tumor cell upon EGFR mediated growth in odontogenic tumors was suggested a different tumor cell growth factor status or microenvironment in cell proliferation mechanism at the cellular level in cysts and tumors of odontogenic origin.

Odontogenic tumor with combined characteristics of adenomatoid odontogenic and calcifying epithelial odontogenic tumors.

A very rare odontogenic epithelial tumor with the combined characteristics of an adenomatoid odontogenic tumor (AOT) and calcifying epithelial odontogenic tumor (CEOT) was found in a 27 year old female. The histopathology, immunohistochemistry of keratin, lectin-binding patterns and distribution of carbonic anhydrase were determined. The nature of the calcified bodies was also examined biophysically. The tumor consisted of cuboidal and columnar odontogenic epithelial cells in the cystic wall, and AOT and CEOT in the central cavity. Odontogenic epithelial cells forming the cyst wall in the CEOT were positive for TK- and KL1-keratins, while that detected with PKK1 antibody was absent in the tumorous epithelium. Lectin binding of tumor epithelial cells was examined with Concanavalin A (Con A), peanut agglutinin (PNA), soybean agglutinin (SBA), dolichos biflorus agglutinin (DBA), wheat germ agglutinin (WGA), ricinus communis agglutinin (RCA-I), and ulex europeus agglutinin I (UEA-I) lectins, and the tumor epithelium indicated existence of glucose, mannose, Gal, GalNAc, and GlcNAc residues. The lectin binding patterns of the calcified material showed an increased intensity by enzymatic pretreatments. With an electron probe X-ray microanalyser (EPMA), the calcified lesions gave a high peak for calcium ion and for phosphorus ion and a low one for magnesium ion, as obtained from line and surface analysis.

[Descriptive and immunohistochemical study of ghost cell keratinization in the calcifying odontogenic cyst]. / Etude signalétique et immunohistochimique de la kératinisation des cellules fantômes du kyste odontogène calcifié.

The calcifying odontogenic cyst (COC) or Gorlin cyst is a rare and benign lesion most often intraosseous, although an appreciable number of cases are peripheral. Two histologic entities are described, one being cystic and the other neoplastic. The cystic type may occur as three variants. The occurrence of ghost cells, although shared with calcifying epithelioma of Malherbe, craniopharyngioma and other odontogenic tumors, represents the most conspicuous feature of the COC. Ghost cells are so called because they stain only faintly with common dies, including eosin. Although seldom studied, it is claimed that ghost cells are keratinized. However, this hypothesis is not universally accepted since electron microscopic studies give evidence that ultrastructural features of ghost cells differ from what is observed during the keratinizing process of the epidermis and oral mucosae. The present study, dealing with one case of COC, combines two complementary techniques: one a Rhodamine B keratin specific staining method and the other an immunohistochemical technique based on the use of a primary antiserum directed against high molecular weight keratins. With the Rhodamine B method, ghost cells and orthokeratinized cells of control gingiva are strongly stained while intermediate cells of the COC are less prominent. On the other hand, with the immunohistochemical technique, intermediate mediate cells of the COC are less prominent. On the other hand, with the immunohistochemical technique, intermediate cells of the COC and high level cells of control epithelium react strongly. Ghost cells of the COC are only faintly labelled and orthokeratinized cells of the control gingiva remain unlabelled. In combination with previous histochemical studies, these results confirm the occurrence of a keratinizing process.(ABSTRACT TRUNCATED AT 250 WORDS)