Ghost cell odontogenic carcinoma arising in dentinogenic ghost cell tumor, peripheral: A case report.

Ghost cell odontogenic carcinoma (GCOC) is an extremely rare intraosseous malignant odontogenic tumor with prominent ghost cell keratinization and dentinoid formation. Here, we present the first case of GCOC arising in dentinogenic ghost cell tumor (DGCT), peripheral. The patient was a man in his 60s with an exophytic mass in the anterior part of lower gingiva. The resected tumor measured 4.5 cm in maximum diameter. Histologically, the nonencapsulated tumor proliferated in the gingiva without bone invasion. It was predominantly composed of ameloblastoma-like nests and islands of basaloid cells with ghost cells and dentinoid in the mature connective tissue, suggesting DGCT, peripheral. As minor components, sheets of atypical basaloid cells and ameloblastic carcinoma-like nests with pleomorphism and high proliferative activity (Ki-67 labeling index up to 40%) consistent with malignancy were identified. CTNNB1 mutation and ß-catenin nuclear translocation were observed in both benign and malignant components. Final diagnosis was GCOC arising in DGCT, peripheral. GCOC shows similar histological features to DGCT. In this unique case without invasion, the cytological atypia and high proliferative activity supports the diagnosis of malignant transformation from DGCT.

Rapid detection of the Streptococcus mutans cnm gene by loop-mediated isothermal amplification.

This study investigated a method using loop-mediated isothermal amplification (LAMP) for the rapid detection of cnm-positive Streptococcus mutans (S. mutans) associated with cerebral microhemorrhage. LAMP amplified the cnm gene plasmid vector, but not human or microbial genomic DNA. The cnm DNA of the cnm-positive S. mutans strain was detected in saliva without DNA extraction after 1 day of culture. This method resulted in a cnm-positive rate of 26.4% in 102 samples, which was higher than that obtained with conventional PCR. In conclusion, LAMP may be used for the detection of cnm-positive S. mutans in a large number of samples.

Detection of MAPK/ERK pathway proteins and KRAS mutations in adenomatoid odontogenic tumors.

OBJECTIVE: This study aimed to assess the frequency of KRAS mutation and its association with the presence of the MAPK/ERK signaling pathway proteins in adenomatoid odontogenic tumors. STUDY DESIGN: Paraffin-embedded tissue samples from nine cases of adenomatoid odontogenic tumor were used. Genomic DNA was extracted from each sample; in one case, genetic mutations in 50 cancer-associated genes were examined by next-generation sequencing. Hotspot mutations in the RAS family were analyzed by Luminex assay using the remaining eight cases. Subsequently, immunohistochemistry for KRAS, CRAF, BRAF, EGFR, ERK, MEK, and BRAFV600E was performed. RESULTS: A KRAS G12D missense mutation was detected in the DNA sequence of the tumor cells, but it was not detected in the stromal tissue. KRAS G12V and KRAS G12R mutations were detected in two and four cases, respectively. For immunohistochemistry, all the cases were EGFR, KRAS, BRAF, CRAF positive, one case was ERK negative,and one case was MEK and ERK negative, all the other remaining cases were MEK and ERK positive. CONCLUSION: KRAS mutation at codon 12 and the presence of MAPK/ERK pathway proteins were detected suggesting their association with tumorigenesis of adenomatoid odontogenic tumors.

Central mucoepidermoid carcinoma arising from glandular odontogenic cyst confirmed by analysis of MAML2 rearrangement: A case report.

Central mucoepidermoid carcinoma (MEC) poses a diagnostic challenge because of its rarity and histological overlap with glandular odontogenic cyst (GOC). In MEC of both salivary glands and jaws, MAML2 arrangement has been well known as the specific gene alteration. We report a case of central MEC arising from GOC diagnosed by MAML2 fusion gene. A 57-year-old male presented a multilocular cystic lesion in left molar region of the mandible. Histopathologically, multiple cysts lined by thin cuboidal or non-keratinized squamous epithelium with small duct-like structures, mucous cells and ciliated cells were present. It was diagnosed as GOC. The recurrent lesion after nine years showed the proliferation of many cystic and solid nests composed of epidermoid, mucous and intermediated cells. Nested PCR revealed CRTC3-MAML2 fusion gene in the recurrent lesion, but not in the primary one. Similarly, MAML-2 rearrangement by FISH analysis was positive in the recurrent lesion, while negative for the primary one, thus confirming the diagnosis of central MEC arising from GOC. Analysis of MAML2 rearrangement can be used as a supportive evidence to distinguish central MEC from GOC.

Pathogenesis of primordial odontogenic tumour based on tumourigenesis and odontogenesis.

OBJECTIVE: Primordial odontogenic tumour (POT) is a rare benign mixed epithelial and mesenchymal odontogenic tumour. POT is composed of dental papilla-like tissue covered with cuboidal to columnar epithelium that resembles to inner and outer enamel epithelium of the enamel organ without dental hard tissue formation. The aim of this study was to examine pathogenesis of POT based on tumourigenesis and odontogenesis. SUBJECTS AND METHODS: Six cases of POT were submitted for study. DNA analysis and transcriptome analysis were performed by next-generation sequencing. Expression of amelogenin, ameloblastin and dentin sialophosphoprotein (DSPP) was examined by immunohistochemistry. RESULTS: There were no gene mutations detected in any of analysed 151 cancer- and 42 odontogenesis-associated genes. Enamel protein-coding genes of Amelx, Ambn and Enam, and dentin protein-coding genes of Col1a1, Dspp, Nes and Dmp1 were expressed, whereas expression of dentinogenesis-associated genes of Bglap, Ibsp and Nfic was negative or very weak suggesting inhibition of dentin formation in POT after odontoblast differentiation. Immunoreactivity of amelogenin, ameloblastin and DSPP was detected in POT. CONCLUSIONS: Pathogenesis of POT is considered to be genetically different from other odontogenic tumours. It is suggested that inhibition of enamel and dentin formation in POT is due to defects in dentin formation process.

A case of primordial odontogenic tumor: A new entity in the latest WHO classification (2017).

Primordial odontogenic tumor (POT) is a rare lesion in the jaw which has been included as a new entity of benign mixed epithelial and mesenchymal odontogenic tumour in the latest World Health Organization (WHO) classification (2017). Only seven cases have been reported. It typically occurs in the posterior mandible. We report an additional case of POT in the maxilla of an 8-year-old girl presenting with an asymptomatic buccal enlargement. A well-defined, unilocular, radiolucent lesion was observed radiographically. Histologically, the tumor was mostly composed of loose fibrous connective tissue resembling dental papilla and a single layer of columnar epithelium covering the periphery of the tumor. In part, cords or nests of epithelium were present in the mesenchyme close to the periphery. Nestin, a marker of odontogenic ectomesenchyme, was positive in the mesenchymal tumor cells. We finally diagnosed the lesion as POT considering the possibility of other odontogenic tumors like ameloblastic fibroma or developing odontoma as a differential diagnosis. The patient shows no recurrence after 16 months. This case is the first report from Japan using this novel diagnosis POT after it was recognized and defined in the latest WHO classification.

Human odontogenic epithelial cells derived from epithelial rests of Malassez possess stem cell properties.

Epithelial cell rests of Malassez (ERM) are quiescent epithelial remnants of the Hertwig's epithelial root sheath (HERS) that are involved in the formation of tooth roots. ERM cells are unique epithelial cells that remain in periodontal tissues throughout adult life. They have a functional role in the repair/regeneration of cement or enamel. Here, we isolated odontogenic epithelial cells from ERM in the periodontal ligament, and the cells were spontaneously immortalized. Immortalized odontogenic epithelial (iOdE) cells had the ability to form spheroids and expressed stem cell-related genes. Interestingly, iOdE cells underwent osteogenic differentiation, as demonstrated by the mineralization activity in vitro in mineralization-inducing media and formation of calcification foci in iOdE cells transplanted into immunocompromised mice. These findings suggest that a cell population with features similar to stem cells exists in ERM and that this cell population has a differentiation capacity for producing calcifications in a particular microenvironment. In summary, iOdE cells will provide a convenient cell source for tissue engineering and experimental models to investigate tooth growth, differentiation, and tumorigenesis.

Ameloblastic carcinoma, secondary type, of the mandible: a case report.

Ameloblastic carcinoma is a rare, odontogenic, malignant tumor that has features of ameloblastoma in addition to cytologic atypia with or without metastasis. It is classified as primary type; secondary type, intraosseous; and secondary type, peripheral according to the World Health Organization classification of 2005. Ameloblastic carcinoma, secondary type, is extremely rare, and few cases have been reported in the English-language literature. The authors report a case of ameloblastic carcinoma, secondary type, arising at the mandible in a 17-year-old Japanese boy.

Two Cases of Temporomandibular Synovial Chondromatosis Associated with Gli1 Gene Mutation.

Synovial chondromatosis (SC) is a rare benign disease involving multifocal generation of ectopic cartilage in the synovial tissue. Herein, we report two cases of SC in the temporomandibular joint: a 38-year-old woman (patient 1) and 39-year-old woman (patient 2). Both patients had trismus, jaw joint noises, and jaw-opening pain in the temporomandibular joint. Cone-beam computed tomography (CT) and magnetic resonance imaging (MRI) in patient 1 showed multiple calcified loose bodies around the right mandibular condyle. In addition, CT and MRI in patient 2 showed multiple calcified loose bodies around the left mandibular condyle and temporal bone perforation. Following establishing a diagnosis of SC, both patients underwent tumor resection via open surgery. In immunohistochemical examinations of the resected tissues, tumor cells showed intense nuclear staining with labeled anti-Gli1 antibody. Gene sequencing revealed that both patients had a homozygous mutation in the Gli1 gene (rs2228226 G>C). In conclusion, we suggest that the Gli1 gene (rs2228226 G>C) may be involved in the etiology of SC.

Sclerosing odontogenic carcinoma with benign fibro-osseous lesion of the mandible: an extremely rare case report.

A case of sclerosing odontogenic carcinoma (SOC) admixed with a benign fibro-osseous lesion (BFOL) is reported herein. A 67-year-old male had paresthesia in the mental region. Computed tomography detected an intragnathic mass that was focally expansile with disappearance of cortical bone, and contained admixed radiolucency and radio-opacity. Under the pathological diagnosis as benign fibro-osseous lesion, it was surgically removed by curettage. Microscopic analysis showed that a few parts of the resected materials contained dispersed thin cords and small nests of epithelial cells accompanied by fibrous stroma. Cellular atypia and mitotic figures were not evident. The diagnosis of BFOL with hyperplastic and metaplastic odontogenic epithelia was ultimately made. Eight months after the operation, the lesion recurred and segmental mandibulectomy was carried out. Histologically, the lesion was predominantly occupied by the fibro-osseous component with irregular-shaped foci of epithelial component. The epithelial component exhibited mostly thin cord or small nest patterns and showed definite perineural infiltration. Immunohistochemically, the epithelial cells were positive for p63, cytokeratin (CK) 6 and CK19, and focally positive for CK7 but negative for vimentin. MIB-1 positive nuclei were inconspicuous. To the best of our knowledge, this report is the first case of SOC with BFOL.

Ghost cell odontogenic carcinoma arising in calcifying odontogenic cyst.

A case of exceptionally rare odontogenic malignant tumor, called ghost cell odontogenic carcinoma, is described. The tumor was considered to be derived from calcifying odontogenic cyst, which had been resected 5 years before. In the present resected specimen, cellular atypia, mitotic activity, Ki-67 labeling index, and p53 positivity were all increased in comparison with the initially resected specimen. This is a valuable case in which malignant transformation from calcifying odontogenic cyst to ghost cell odontogenic carcinoma was proven by the histopathologic and immunohistochemical findings. Pathologists should be aware of this rare entity.

Current status of dental metal allergy in Japan.

PURPOSE: To assess the current status of patients with dental metal allergies in Japan. METHODS: This study analyzed dental metal allergy in 1225 patients (1:3 male to female ratio; average age 53.0 ±16.5 years), including 300 who were scheduled to undergo dental implant surgery, between 2006 and 2016. For diagnosis of metal allergy, patch tests using metal allergens were performed. Additionally, when necessary, metal element analysis of dental alloys was performed in the mouths of some patients using an X-ray fluorescence analyzer for those who exhibited positive reactions. RESULTS: Among 925 patients (i.e., excluding those scheduled to undergo dental implant surgery [n=300]), nearly one-half (44.0%) exhibited a positive response to any metal element in the patch test. The positivity rates were as follows: nickel (22.5%); palladium (14.8%); and zinc (11.5%). Almost one-half (42.3%) of the patients had diseases associated with metal allergy. Among patients who exhibited a positive reaction to any metal element in the patch test, more than two-thirds (67.9%) had dental alloys containing the positive metal element(s). One-half (55.6%) of the patients who underwent treatment to remove the metal experienced improvement in symptoms. In patients who underwent patch testing as an implant preoperative examination, several (2.7%) exhibited a positive reaction to titanium. CONCLUSIONS: Dental metals, including nickel, palladium and zinc, which are indispensable to dental treatment in Japan, had high positivity rates in patch testing, and one-half of the patients improved following removal of the metal. Additionally, there were several patients with allergy to titanium.

Immortalization and characterization of human dental pulp cells with odontoblastic differentiation.

OBJECTIVE: To immortalize human dental pulp (HDP) cell showing stable growth and high mineralization activities in vitro. DESIGN: HDP cells were obtained from a healthy third molar and immortalized by transfection with human telomerase transcriptase (hTERT) gene. To examine the characters of hTERT transfected HDP (HDP-hTERT) cells, we examined expression of mRNA for dentin sialophosphoprotein (DSSP), type I collagen (COLI), alkaline phosphatase (ALP) and bone sialoprotein (BSP) by RT-PCR. In addition, we examined ALP activity by biochemical method and nodule formation by alizarin red S (ALZ) staining. RESULTS: HDP-hTERT was obtained by transfection with hTERT gene. These cells bypassed the senescence and grew over 120 population doublings (PDLs) without significant growth retardation. High expression of hTERT was confirmed in HDP-hTERT by RT-PCR and showed remarkable telomerase activity. Both HDP-original (HDP-ori) and HDP-hTERT expressed DSSP, COLI, ALP and BSP mRNA and showed ALP activity and ALZ staining at the same levels. CONCLUSIONS: We were able to establish a cell line of immortalized human dental pulp cells with odontoblastic differentiation which will be a useful cell model for studying the mechanism of proliferation and differentiation of odontoblasts.

Overexpression of Aurora-A potentiates HRAS-mediated oncogenic transformation and is implicated in oral carcinogenesis.

Aurora kinases are known to play a key role in maintaining mitotic fidelity, and overexpression of aurora kinases has been noted in various tumors. Overexpression of aurora kinase activity is thought to promote cancer development through a loss of centrosome or chromosome number integrity. Here we observed augmentation of G12V-mutated HRAS-induced neoplastic transformation in BALB/c 3T3 A31-1-1 cells transfected with Aurora-A. Aurora-A-short hairpin RNA (shRNA) experiments showed that the expression level of Aurora-A determines susceptibility to transformation. Aurora-A gene amplification was noted in human patients with tongue or gingival squamous carcinoma (4/11). Amplification was observed even in pathologically normal epithelial tissue taken at sites distant from the tumors in two patients with tongue cancer. However, overexpression of Aurora-A mRNA was observed only within the tumors of all patients examined (11/11). Our data indicate that Aurora-A gene amplification and overexpression play a role in human carcinogenesis, largely due to the effect of Aurora-A on oncogenic cell growth, rather than a loss of maintenance of centrosomal or chromosomal integrity.

Invasion and metastasis of oral cancer cells require methylation of E-cadherin and/or degradation of membranous beta-catenin.

The extent of lymph node metastasis is a major determinant in the prognosis of oral squamous cell carcinoma (OSCC). Abnormalities of cell adhesion molecules are known to play an important role in invasion and metastasis of cancer cells through the loss of cell-to-cell adhesion. In this study, we isolated highly invasive clones from an OSCC cell line established from a lymph node metastasis by using an in vitro invasion assay method and compared the abnormalities of cell adhesion molecule E-cadherin and beta-catenin in these cells. The isolated, highly invasive clones showed significant invasive capacity and reduction of E-cadherin and membranous beta-catenin protein in comparison with parent cells. We found that reduced expression of E-cadherin was due to methylation of its promoter region. In fact, most invasive and metastatic area of OSCCs showed reduced expression and methylation of E-cadherin. Moreover, we found that reduced expression of membranous beta-catenin was due to its protein degradation. Reduced expression of membranous beta-catenin was also found frequently in invasive and metastatic areas of OSCCs. In summary, invasion and metastasis of OSCC cells require methylation of E-cadherin and/or degradation of membranous beta-catenin. In addition, we suggest that the method of isolation of highly invasive clones may be useful for studies aimed at discovering novel genes involved in invasion and metastasis.

Peripheral ameloblastoma with histologically low-grade malignant features of the buccal mucosa: a case report with immunohistochemical study and genetic analysis.

Peripheral ameloblastoma (PA), a rare and unusual variant of odontogenic tumors, comprises about 1% of all ameloblastomas. PA is an exophytic growth localized to the soft tissues overlying the tooth-bearing areas of the jaws, and the initial diagnosis is often fibrous epulis. PA with histologically low-grade malignant features is extremely rare. We report a case of peripheral ameloblastoma with histologically low-grade malignant features in a 69-year-old woman that presented with a hemorrhage from a tumor on the right buccal mucosa. The tumor was surgically removed by blunt dissection, with no evidence of recurrence after two years and six months. After the case presentation, microscopic and genetic findings are discussed.

Establishment of an oral squamous cell carcinoma cell line with high invasive and p27 degradation activities from a lymph node metastasis.

The extent of lymph node metastasis is a major determinant in the prognosis of oral squamous cell carcinoma (OSCC). We present here a new OSCC cell line, MSCC-1, established from a lymph node metastasis of a patient with OSCC of gingiva. First, we examined the expression of p27, p53 and Ki-67 in non-neoplastic mucosa, primary and metastatic cancer lesions by immunohistochemistry. Metastatic cancer cells in the lymph node showed the reduced expression of p27 in comparison with cancer cells in the primary lesion. Cancer celLs both in the primary and metastatic lesions showed overexpression of p53 and Ki-67. Overexpression of p53 and reduced expression of p27 in MSCC-1 cells were also determined by western blot analysis. To characterize MSCC-1 cells, furthermore, we examined the invasive activity and cell proliferation of MSCC-1, comparing with those of other OSCC cell lines, HSC-2 and HSC-3 cells. The invasive capacity of MSCC-1 cells was significant higher than HSC-2 and HSC-3 cells, but cell growth of MSCC-1 cells was slower than HSC-2 and HSC-3 cells. Moreover, we examined the p27 degradation activity by in vitro degradation assay. Interestingly, MSCC-1 cells have the strongest p27 degradation activity among the OSCC cell lines examined. In the present study, we newly established MSCC-1 cells with strong invasiveness and p27 degradation activity from a metastatic lesion. These findings suggest that high activity of p27 degradation may concern with invasiveness of OSCC cells and that MSCC-1 cells can be a useful cell model for studying the detailed mechanism of p27 degradation, invasion and metastasis of OSCC.

Atypical carcinoid (neuroendocrine carcinoma) of the gingiva: counterpart of a laryngeal tumor.

Intraoral localization of neuroendocrine carcinoma, usually called Merkel cell carcinoma, is extremely rare. A case of neuroendocrine carcinoma that was a counterpart of laryngeal neuroendocrine carcinoma but was not a Merkel cell carcinoma, occurring at the mandibular gingiva in a 69-year-old Japanese man, is described. The tumor formed a cauliflower-like mass, measuring 20 x 20 mm, with a small area of necrosis. A computed tomography image showed metastasis in the right submandibular lymph node. Histopathologically, the tumor was composed of immature, small round cells that formed anastomosing trabecular nests. Few mitotic and no necrotic features were observed in the nests. Immunohistochemical studies showed positive staining for chromogranin, synaptophysin and neuron-specific enolase in the tumor nests. We diagnosed it as an atypical carcinoid (neuroendocrine carcinoma), a counterpart to the same type of tumor occurring in the larynx. The present case is an extremely rare case of neuroendocrine carcinoma without the feature of Merkel cell carcinoma arising from the gingiva.

Odontogenic carcinoma with dentinoid: a new odontogenic carcinoma.

Dentinoid is an integral part of some odontogenic tumors. This article describes the clinico-pathological features of three cases of odontogenic carcinomas with dentinoid (OCD). A comparison of these with previously reported cases of dentinoid-producing epithelial odontogenic tumors allowed us to identify another six cases that may be considered as examples of OCD. Six cases occurred in the mandible and three in the maxilla, all developing behind the canines. There was no sex predilection (five men and four women; age range 14-61 years, mean 38.1). Pain or discomfort was mentioned in five cases, four of which showed tooth resorption. All cases appeared initially as well-defined radiolucencies, five of which showed variable amounts of calcified material. Recurrences were recorded in three instances, but no evidence of metastasis has been found. Seven cases were composed predominantly or entirely of clear cells, usually with minimal cellular atypia and variable mitotic activity; however, in all cases there was evidence of tumor infiltration into adjacent tissues, including the presence of perineural invasion in two tumors. Those cases in which no reference was made to the presence of clear cells exhibited evident mitotic activity and cellular pleomorphism. The epithelium in OCD does not produce buds or enamel organ-like structures such as those found in ameloblastic fibro-dentinoma and this tumor does not contain a mesenchyme-like connective tissue resembling dental papilla as observed in several mixed odontogenic tumors. Based on the existing data and the present series of cases, OCD appears to represent a distinct entity.