Gene mutation analysis and immunohistochemical study of beta-catenin in odontogenic tumors

In the present study the significance of nuclear/cytoplasmic expression of beta-catenin (CTNNB1) and mutation of the CTNNB1 gene (CTNNB1) in odontogenic tumors was examined. Six ameloblastomas (five follicular ameloblastomas and one plexiform ameloblastoma) and three malignant odontogenic tumors (one metastasizing ameloblastoma, one ameloblastic carcinoma, and one primary intraosseous odontogenic carcinoma) were investigated for CTNNB1 expression and CTNNB1 mutation. Immunohistochemically, all follicular ameloblastomas and one primary intraosseous odontogenic carcinoma exhibited focal and moderate nuclear/cytoplasmic expression of CTNNB1, whereas the plexiform ameloblastoma and the remaining two malignant odontogenic tumors had entirely membranous expression. CTNNB1 mutation at codon 40 of exon 3 was found in one of the six follicular ameloblastomas. The other five follicular ameloblastomas, the plexiform ameloblastoma, and the three malignant odontogenic tumors did not show mutation in exon 3 of CTNNB1. These findings further confirmed that CTNNB1 mutation is not frequent in ameloblastoma and malignant odontogenic tumors, although the abnormality of Wnt signaling may be associated with some of these tumors.     

A clinicopathological study of malignant odontogenic tumours

Chaisuparat R, Sawangarun W & Scheper M A
(2012) Histopathology  61, 107–112 A clinicopathological study of malignant odontogenic tumours Aims: Malignant odontogenic tumours (MOTs) are rare neoplasms occurring primarily within the jaw. The objective of this study was to determine the incidence, demographics and clinicopathological features of the MOTs from two institutions. Methods and results: The records of the Department of Oral Pathology, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand and the Department of Oncology and Diagnostic Sciences, Dental School, University of Maryland, Baltimore, USA were searched from 1991 to 2010; we identified 17 cases of previously diagnosed MOTs. All cases were reviewed independently of the previous diagnosis by two blinded oral pathologists and reclassified based on the 2005 World Health Organization classification of head and neck tumours. In this study we describe in detail these 17 cases which presented with an average age of 50.29 years and a male to female ratio of 2.4:1. These cases included five ameloblastic carcinomas, four atypical ameloblastomas, three primary intraosseous squamous cell carcinomas, three intraosseous mucoepidermoid carcinomas and two clear cell odontogenic carcinomas. All cases were treated by surgical resection and one patient with ameloblastic carcinoma received postoperative radiotherapy. Conclusions: Malignant odontogenic tumours are considered rare central odontogenic lesions. Awareness of their existence, rapid diagnosis and successful treatment using surgery, radiation and/or chemotherapy is critical to patient survival.     

Allelic loss of tumor suppressor genes in ameloblastic tumors.

Ameloblastoma is an odontogenic tumor with a variety of histologic appearances and an unpredictable biologic behavior. Little is known about allelic losses of tumor suppressor genes in ameloblastomas. This study surveyed DNA damage in ameloblastomas and correlated this with histologic sub-type and clinical outcome. There were 12 ameloblastomas (two peripheral, eight solid, and two unicystic) and three ameloblastic carcinoma studied for loss of heterozygosity of tumor suppressor genes on chromosomes 1p, 3p, 9p,10q, and 17p (L-myc, hOGG1, p16, pten, and p53). The frequency of allelic loss and the intratumoral heterogeneity were calculated. L-myc (71% frequency of allelic loss) and pten (62% frequency of allelic loss) had the most frequent allelic losses. Overall frequency of allelic loss and intratumoral heterogeneity were higher in mandibular and in unicystic tumors and lower in tumors that recurred/metastasized. The rate of allelic loss in the three carcinomas was similar to that seen in benign tumors. The frequency of allelic loss and intratumoral heterogeneity did not correlate with age, gender, histologic subtype, or prognosis. Since tumors that behaved aggressively did not harbor more allelic losses, it is likely that DNA damage in ameloblastomas and ameloblastic carcinomas is sporadic and cumulative. We conclude that other genetic or epigenetic mechanisms may be responsible for malignant behavior in ameloblastic carcinomas.     

Immunoexpression of integrins in ameloblastoma, adenomatoid odontogenic tumor, and human tooth germs

The expression of integrins alpha2beta1, alpha3beta1, and alpha5beta1 in 30 ameloblastomas (20 solid and 10 unicystic tumors), 12 adenomatoid odontogenic tumors (AOTs), and 5 human tooth germs in different stages of odontogenesis was analyzed. The distribution, location, pattern, and intensity of immunohistochemical expression were evaluated. Intensity was analyzed using scores (0 = absence, 1 = weak staining, and 2 = strong staining). No difference in the immunoexpression of the integrins was observed between solid and unicystic ameloblastomas. When these two ameloblastoma types were pooled into a single group, the following significant differences were found: immunoexpression of integrin alpha2beta1 was stronger in ameloblastomas than in AOTs and tooth germs, and the expression of integrin alpha5beta1 was stronger in ameloblastomas than in AOTs. The lack of detection of integrin alpha3beta1 in tooth germs and its detection in the odontogenic tumors studied suggest that this integrin might be used as a marker of neoplastic transformation in odontogenic tissues.     

Immunohistochemical demonstration of an enamel sheath protein, sheathlin, in odontogenic tumors

Enamel proteins can be useful markers for assessment of the functional differentiation of neoplastic epithelium and the nature of extracellular matrices in odontogenic tumors. In the present study, we examined immunohistochemical localization of sheathlin, a recently cloned enamel sheath protein, in various odontogenic tumors to evaluate functional differentiation of tumor cells and the nature of hyalinous or calcified matrices in odontogenic neoplasms. Distinct immunolocalization of sheathlin was observed in the immature enamel of the tooth germ at the late bell stage. Secretory ameloblasts facing the enamel matrix also showed positive staining in their cytoplasm. Definite localization of sheathlin was demonstrated in the enamel matrix in odontogenic tumors with inductive dental hard tissue formation such as ameloblastic fibroodontomas and odontomas. Immunoexpression of sheathlin was, furthermore, demonstrated in eosinophilic droplets in solid nests of adenomatoid odontogenic tumor (AOT) and ghost cells in the epithelial lining of calcifying odontogenic cyst (COC). In AOT, cells facing the eosinophilic droplets also expressed the protein in their cytoplasm. There was neither intracellular staining for sheathlin in the tumor cells nor extracellular staining in the matrix of ameloblastomas and calcifying epithelial odontogenic tumors. Dentin, dysplastic dentin-like hyaline material and cementum in the tumors examined were negative for sheathlin. These results show that immunodetection of sheathlin is a useful marker for functional differentiation of secretory ameloblasts and enamel matrix, which is often hard to differentiate from other hard tissues in odontogenic tumors. Our findings from the view point of sheathlin expression support that the tumor cells of ameloblastomas do not attain full differentiation into functional ameloblasts. It is very interesting that epithelial cells in odontogenic tumors can differentiate into functional ameloblasts without induction by odontogenic mesenchyme, as shown by immunoexpression of sheathlin in eosinophilic droplets within solid epithelial sheets in AOT and ghost cells in the epithelial lining of COC where inductive participation of mesenchymal cells was most unlikely. Received: 19 May 1999 / Accepted: 27 September 1999     

CD56 (NCAM) expression in ameloblastomas and other odontogenic lesions

Cairns L, Naidu A, Robinson C M, Sloan P, Wright J M & Hunter K D
(2010) Histopathology 57, 544–548
CD56 (NCAM) expression in ameloblastomas and other odontogenic lesions Aims: Ameloblastomas recapitulate certain elements of tooth formation. CD56 is expressed by a variety of cells and is used in tumour diagnosis, but is also expressed in the enamel organ during tooth development. The aim of this study was to describe the expression of CD56 in odontogenic lesions with particular reference to the differential diagnosis of ameloblastoma and odontogenic keratocyst. Methods: Cases were selected from the pathology archives at Glasgow Royal Infirmary, Glasgow, Royal Victoria Infirmary, Newcastle and Department of Diagnostic Sciences, Texas A&M Health Science Center Baylor College of Dentistry, Dallas. The study population included 38 ameloblastomas, 19 odontogenic keratocysts and a number of other odontogenic lesions, including nine compound odontomes. All sections were examined for CD56 immunoreactivity and the extent of staining was recorded. Results: Thirty‐seven of 38 (97%) ameloblastomas expressed CD56 on the cell membrane of peripheral cells in tumour nests (16 extensively, 21 focally). Immunoreactivity was lost in areas of inflammation, acanthomatous differentiation, in areas of cystic change and upon fusion with overlying surface epithelium. One odontogenic keratocyst expressed CD56 (5%, P < 0.0001). CD56 was expressed very focally in two odontomes, exclusively in stratum intermedium‐like cells. Conclusions: CD56 expression in odontogenic epithelium is highly suggestive of ameloblastoma and can help in differentiating this from odontogenic keratocyst.     

Ameloblastoma and adenomatoid odontogenic tumor: the role of alpha2beta1, alpha3beta1, and alpha5beta1 integrins in local invasiveness and architectural characteristics

Ameloblastoma is an odontogenic neoplasm characterized by local invasiveness and a tendency toward recurrence, whereas adenomatoid odontogenic tumor (AOT) is an indolent neoplasm. The objective of the present study was to immunohistochemically analyze the role of alpha2beta1, alpha3beta1, and alpha5beta1 integrins in the cellular events and cell-matrix interactions that occur in these tumors and their consequent repercussions on the architectural arrangement and biologic behavior of these lesions. Paraffin-embedded specimens from 30 ameloblastomas (20 solid and 10 unicystic tumors) and 12 AOTs were submitted to immunohistochemistry using the catalyzed signal amplification system. A difference in the pattern of integrin expression was observed between the various histologic types of ameloblastoma. No significant difference in labeling intensity was observed between unicystic and solid ameloblastomas, but comparison between ameloblastomas and AOT showed a significantly stronger expression of alpha5beta1 integrin in the former (P < .05). Our findings suggest an important role of the integrins studied in the architectural characteristics of ameloblastomas and AOTs and a possible participation of alpha5beta1 integrin in the mechanism of local invasion of ameloblastomas.     

Use of calretinin in the differential diagnosis of unicystic ameloblastomas

AIMS: Calretinin, a 29-kDa calcium-binding protein is expressed widely in normal human tissues and tumours including both unicystic and solid and multicystic ameloblastomas. The histological distinction between unicystic ameloblastomas and certain non-neoplastic odontogenic cysts can be problematic. The objective of this study was to determine whether calretinin was expressed in the lining epithelium of odontogenic keratocysts, residual and dentigerous cysts and to determine whether this calcium-binding protein could be used to distinguish these cysts from the unicystic ameloblastoma. METHODS AND RESULTS: The lining epithelium in 22 cases of odontogenic keratocyst, 26 cases of residual cyst and 20 cases of dentigerous cyst were examined for the expression of calretinin. No positive epithelial staining was observed in any of these cystic lesions. In comparison, however, 81.5% of cases of unicystic ameloblastoma showed a coarse dark brown staining of the more superficial epithelial cell layers. Scattered positive stromal and epithelial cells were present; these were interpreted as mast cells. CONCLUSIONS: Calretinin appears to be a specific immunohistochemical marker for neoplastic ameloblastic epithelium and we suggest that it may be an important diagnostic aid in the differential diagnosis of cystic odontogenic lesions and ameloblastic tumours.     

Immunohistochemical localization of large chondroitin sulfate proteoglycan in odontogenic tumor

The present study investigated the localization of versican in odontogenic tumors by immunohistochemistry, using paraffin-embedded sections obtained from 27 patients with odontogenic tumors (17 ameloblastomas, 1 adenomatoid odontogenic tumor, 4 odontogenic keratocysts, 1 calcifying odontogenic cyst, 2 ameloblastic fibromas, and 2 malignant ameloblastomas). Deparaffinized sections were immersed in a buffered 1 : 1000 solution of an antibody, 5D5 (raised against a large chondroitin sulfate proteoglycan from bovine sclera), which mainly recognizes versican. All samples showed a positive reaction for versican in connective tissues, whereas positive staining of epithelial nests was observed in only some samples. The positive staining in epithelial nests was in areas showing stellate reticulum-like, cuboidal, columnar cells at the periphery, and tear-drop structures. These results indicated that versican might be involved in, at least in part, the morphogenesis of neoplastic epithelium and mesenchymal tissues in odontogenic tumors.     

Expression of p21RAS in odontogenic tumors.

Using an immunohistochemical assay 10 benign odontogenic tumors were evaluated for expression of the HRAS- and KRAS-encoded gene products p21RAS. Overexpression of p21RAS was found in ameloblastomas, ameloblastic fibromas and odontogenic myxomas compared with normal human developing teeth. The highest expression was noted in a recurrent plexiform ameloblastoma in which almost 100% of the tumor cells were brightly reactive. In general, p21RAS was preferentially expressed in ectodermal cells of odontogenic tumors, consistent with the findings in the tooth germs. The significance of p21RAS expression is considered in relation to the biological behavior of ameloblastomas.     

Ameloblastic fibroma: A fine-needle aspiration case report

Fine-needle aspiration biopsy of an ameloblastic fibroma, an unusual odontogenic tumor related to ameloblastoma, was performed on a 38-yr-old man with a slowly enlarging left facial mass. Aspiration of the tumor yielded a cellular sample composed of a mixture of mesenchymal and epithelial cells, arranged, respectively, in thick mats and complex solid structures outlined by columnar cells with central regions reminiscent of stellate reticulum. A diagnosis of odontogenic tumor was conferred, and the lesion was surgically biopsied and then resected. The key cytologic feature distinguishing this lesion from other odontogenic tumors was fragments of hypercellular stroma. The differential diagnosis includes ameloblastoma, ameloblastic fibrosarcoma, other odontogenic tumors, intraosseous adenoid cystic carcinoma, trabecular adenoma, and basal-cell carcinoma. Diagn. Cytopathol. 1997; 17:280–286. © 1997 Wiley-Liss, Inc.     

Comparative expression of calretinin in selected odontogenic tumours: a possible relationship to histogenesis

Aims:  Calretinin, a calcium-binding protein, is expressed primarily in certain subtypes of neurons. It has also been reported to be present in mesotheliomas and other tumours. The aim was to determine the expression of calretinin in selected odontogenic neoplasms.
Methods and results:  Immunohistochemistry for calretinin was performed on 55 odontogenic tumours consisting of 20 solid ameloblastomas, five calcifying epithelial odontogenic tumours, 10 adenomatoid odontogenic tumours, 10 ameloblastic fibromas and 10 odontogenic myxomas. The distribution, intensity, pattern and localization of immunoreactive cells were determined by conventional light microscopy. χ² test was used for statistical analysis and P  < 0.05 was considered to be significant. All 20 ameloblastomas showed intense immunopositivity with a diffuse distribution pattern. None of the other neoplasms was reactive with calretinin. Differences in the proportion of calretinin expression between groups were statistically significant at P  < 0.001.
Conclusions:  Considering that ameloblastomas, in contrast to the other studied tumours, were consistently reactive for calretinin, this protein may have a role in the pathogenesis of this aggressive neoplasm.     

Cytopathologic features of secondary peripheral ameloblastic carcinoma: A case report

Peripheral ameloblastic carcinoma is an extremely rare odontogenic tumor derived from the remnants of dental lamina and/or mucosal epithelium of the oral mucosa. We present a case of secondary peripheral ameloblastic carcinoma of the mandibular gingiva. The patient was a 71‐year‐old man with gingival swelling and persistent bleeding. Exfoliative cytology revealed cohesive clusters composed of basaloid cells with nuclear atypia and various forms of keratinized cells of dysplastic squamous appearance. Some cell groups had a peripheral palisade. Histology of the biopsy and surgically removed specimens revealed characteristic features resembling squamous cell carcinoma, basal cell carcinoma, and benign follicles of ameloblastoma. These neoplastic structures, as well as proliferation and elongation of the mucosal epithelium, comprised an extensive network. The varied cytopathologic findings may be related to proliferation and transformation of basal cells of the mucosal epithelium toward ameloblastic carcinoma and variable squamous differentiation. Diagn. Cytopathol. 2011;39:354–358. © 2010 Wiley‐Liss, Inc.     

Aspiration cytology of ameloblastic fibroma: a diagnostic challenge

Ameloblastic fibroma of the jaw is a rare, benign mixed odontogenic tumor, having little tendency for local invasion and a low recurrence rate. Cytologic distinction from ameloblastoma, ameloblastic fibrosarcoma, and intraosseous adenoid cystic carcinoma is necessary, in view of the different biologic behavior. A painful, slow-growing swelling of the jaw in a 5-yr-old child clinicoradiologically considered as a benign cystic lesion was aspirated. Sheets of small monomorphic epithelial cells with peripheral palisading by columnar cells were seen on cytology smears. The striking feature was central hyaline globules in some tubules. A cytologic possibility of adenomatoid odontogenic tumor was suggested. Histopathology, however, confirmed it to be an ameloblastic fibroma.     

Comprehensive keratin profiling reveals different histopathogenesis of keratocystic odontogenic tumor and orthokeratinized odontogenic cyst

Keratocystic odontogenic tumor is a cystic lesion that behaves more aggressively than other jaw cysts. One of its characteristic histologic features is a parakeratinized uniform layer of lining epithelium. A jaw cyst lined with orthokeratinized epithelium is called an orthokeratinized odontogenic cyst. These keratinized jaw cysts are thought to be separate entities, although their histopathogenesis has not been fully assessed. To better understand these lesions, we performed comprehensive immunohistochemical profiling of the keratin expression of each. Orthokeratinized odontogenic cysts expressed keratin 1, keratin 2, keratin 10, and loricrin, suggesting differentiation toward normal epidermis. Keratocystic odontogenic tumors expressed keratin 4, keratin 13, keratin 17, and keratin 19, which is a unique expression pattern reminiscent of a mucosal squamous epithelium and an epithelial appendage. In neonatal rat tooth germ, cells strongly positive for keratin 17 and keratin 19 were observed, specifically in the dental lamina, implying the origin of keratocystic odontogenic tumor. GLI2, a downstream effector of hedgehog signaling, was significantly expressed in keratocystic odontogenic tumor and basal cell carcinoma, accompanied with robust expression of keratin 17, mammalian target of rapamycin, and BCL2. The expression of these GLI2- or keratin 17-related factors was not significantly observed in orthokeratinized odontogenic cysts. These findings provide evidence to support the viewpoint that keratocystic odontogenic tumor and orthokeratinized odontogenic cyst are separate entities, and furthermore suggest their characteristic histology, pathogenesis, and biological behaviors.     

Midkine expression correlating with growth activity and tooth morphogenesis in odontogenic tumors

Midkine (MK; a low molecular weight heparin-binding growth factor) is a multifunctional cytokine. MK plays a role in morphogenesis of many organs including teeth through epithelial-mesenchymal interactions. We immunohistochemically examined MK expression in various human odontogenic tumors. There was no difference in positive rate and intensity of MK between benign odontogenic tumors and their malignant counterparts. Ameloblastoma showed MK localization in the peripheral columnar cells in budding processes from the parenchyma, which frequently expressed proliferating cell nuclear antigen. MK was also preferentially expressed in keratinized cells in acanthomatous ameloblastoma and keratocystic odontogenic tumor. In odontogenic mixed tumors except for odontoma, intense immunoreactivity to MK was found in epithelial follicles, the surrounding odontogenic ectomesenchymal tissue, and the basement membrane between them. Intensity in the odontogenic ectomesenchyme decreased in relation to distance from the epithelial follicles. No expression was found in tumor cells associated with production of dental hard tissues in odontogenic mixed tumors including odontoma. These findings suggested that MK is involved in the reciprocal interaction between odontogenic epithelium and odontogenic ectomesenchymal tissue in areas without dental hard tissue formation in odontogenic mixed tumors. Coexpression of MK and proliferating cell nuclear antigen was also observed in epithelial follicles and highly cellular nodules in the ectomesenchyme of odontogenic mixed tumors. MK is considered to mediate growth activity of odontogenic tumors and cell differentiation of odontogenic mixed tumors through molecular mechanisms similar to those involved in morphogenesis of the tooth.     

Comparative expression of syndecan-1 and Ki-67 in peripheral and desmoplastic ameloblastomas and ameloblastic carcinoma

The aims of the present study were to examine whether the pattern of syndecan-1 expression correlates with cellular proliferation index in desmoplastic ameloblastomas (DA), peripheral ameloblastomas (PA) and ameloblastic carcinomas (AC), and to compare with that previously reported for solid (SA) and unicystic (UA) variants of ameloblastoma. Immunohistochemistry was performed for syndecan-1 and Ki-67 in seven ameloblastomas (four DA and three PA) and three AC. Expression of syndecan-1 was related to the histological subtype of tumors and, in the case of malignancy, to lower expression levels observed in AC (22.5%) than in PA (47.5%) or DA (77.5%) ( P < 0.05). Syndecan-1 expression correlated inversely with Ki-67 proliferative index: the expression was lower in both types of ameloblastomas (1.5% in DA and 6.4% in PA) than in AC (41.2%; P < 0.05). The present results suggest that the decrease in syndecan-1 expression and increase in the Ki-67 index observed in AC is in accordance with its higher aggressiveness as compared to the rare DA and PA. Interestingly, DA had a lower proliferation index as well as the highest levels of syndecan-1 expression. These data suggest that DA differ from the other types of intraosseous ameloblastomas but more studies are necessary to better understand the role of this protein as a marker in the biological behavior of the epithelial odontogenic neoplasms.     

牙源性钙化囊性瘤临床病理研究

目的探讨牙源性钙化囊性瘤(calcifying cystic odontogenic tumor,CCOT)的临床病理分型对治疗预后的影响。方法对39例CCOT的临床表现、X线影象、病理特征及治疗随访资料等进行回顾性分析。结果 39例中男性26例,女性13例,平均年龄29.6岁;病变位于下颌骨21例,上颌骨18例;临床多以颜面部肿胀就诊。X线主要表现为颌骨内界限清楚的放射透光区,单房或多房,其中伴有钙化斑点或团块。镜下均可见到特征性的影细胞,可分为4种类型:单纯囊肿型(17例)、CCOT伴牙瘤型(12例)、CCOT伴成釉细胞瘤增生型(7例)、CCOT伴其他良性牙源性肿瘤型(3例:伴成釉细胞纤维瘤2例,伴成釉细胞纤维牙瘤1例)。治疗均采用囊肿摘除术或刮治术,获得随访33例,复发6例,其中3例复发者均为CCOT伴成釉细胞瘤增生型且有囊壁内浸润(1例复发为牙源性影细胞瘤,1例20年后复发恶变为牙源性影细胞癌)。结论 CCOT伴成釉细胞瘤增生且有囊壁内浸润型行单纯囊肿摘除术或刮治术容易复发,可形成牙源性影细胞瘤或恶变成牙源性影细胞癌,此型肿瘤的手术范围应适当扩大并进行长期随访。