Clear cell odontogenic tumor: histochemical and ultrastructural features

Exuberant clear cell odontogenic carcinoma of the mandible harboring EWSR1 rearrangement: Report of a rare case and a literature review

Clear cell odontogenic carcinoma (CCOC) is a rare malignant odontogenic tumour (MOT) that mainly affects the mandible, with a slight female predominance in adult patients. In this study, we described an exuberant CCOC in mandible of a 22-year-female patient. On radiographic examination, a radiolucent lesion in the region of tooth 36 to 44 with tooth displacement and alveolar cortical resorption was observed. Histopathological study revealed a malignant neoplasm of the odontogenic epithelium, composed of PAS-positive clear cells and immunoreactivity for CK5, CK7, CK19, p63. The Ki-67 index was low (<10 %). Fluorescent in situ hybridization revealed EWSR1 gene rearrangement. The diagnosis of CCOC was established and the patient was referred for surgical treatment.

Clear cell odontogenic carcinoma: Case report of a deceptive pathology

Clear cells are associated with numerous physiological and pathological conditions. Odontogenic cysts and tumors can arise from physiological clear cells like rests of dental lamina. One such clear cell neoplasm is clear cell odontogenic carcinoma (CCOC) that is associated with aggressive clinical behavior, metastasis and low survival rate. With <80 cases reported so far, it is a rare entity. Initially described as a clear cell odontogenic tumor considering it as a benign but invasive neoplasm, it was later termed as CCOC owing to its infiltrative nature with a marked tendency for local recurrence, regional nodal spread and possible distant, mainly pulmonary, metastasis. Reported here is a case of CCOC affecting mandible of a 55-year-old female along with its immunohistochemical workup.

Misdiagnosis of ameloblastoma in a patient with clear cell odontogenic carcinoma: a case report

Clear cell odontogenic carcinoma (CCOC), a rare tumor in the head and neck region, displays comparable properties with other tumors clinically and pathologically. In consequence, an incorrect diagnosis may be established. A 51-year-old male patient who was admitted to the Department of Oral and Maxillofacial Surgery at Pusan National University Dental Hospital was initially diagnosed with ameloblastoma via incisional biopsy. However, the excised mass of the patient was observed to manifest histopathological characteristics of ameloblastic carcinoma. The lesion was ultimately diagnosed as clear cell odontogenic carcinoma by the Department of Oral Pathology of Pusan National Dental University. Therefore, segmental mandibulectomy and bilateral neck dissection were performed, followed by reconstruction with fibula free flap and reconstruction plate. Concomitant chemotherapy radiotherapy was not necessary. The patient has been followed up, and no recurrence has occurred 6 months after surgery.

Immunohistochemical Expression of GLUT-1 and HIF-1α in Tooth Germ, Ameloblastoma, and Ameloblastic Carcinoma

Hypoxia-inducible factor-1α (HIF-1α) promotes proteins that enable cell survival during hypoxia, such as glucose transporter 1 (GLUT-1). Their coexpression has been associated with aggressiveness in malignancies and has not been studied in odontogenic tumors. Immunohistochemical expression of HIF-1α and GLUT-1 was analyzed in 13 tooth germs (TGs), 55 ameloblastomas (AMs), and 3 ameloblastic carcinomas (ACs). HIF-1α was negative in all TGs, and just 1 case of AM and 1 of AC had nuclear positivity. GLUT-1 expressed in ameloblastic cells of all TGs, AMs, and ACs, with an increasing intensity, respectively, and was significantly higher in solid AM than in unicystic AM (P = .041). Absence of nuclear HIF-1α in TGs and most AMs suggest that GLUT-1 may be induced by alternative pathways to hypoxia. However, in ACs, HIF-1α may be activated; however, to confirm this, additional cases are needed. GLUT-1 overexpression could be related to aggressiveness in AMs and ACs and must represent a normal metabolite in TGs.

Calcifying ghost cell odontogenic tumor (CGCOT) with predominance of clear cells: a case report with important diagnostic considerations

An 18-year-old female reported painful swelling in the left maxillary region 4 months after the extraction of tooth #15. Because incisional biopsy suggested ameloblastoma with clear-cell changes, segmental resection was performed. The microscopic examination of the excised tissue revealed histomorphologic diversity, with features of typical calcifying ghost cell odontogenic tumor (CGCOT) and a significant clear-cell component constituting more than 50% of the tumor mass without any features of malignancy. Clear cells were periodic acid-Schiff (PAS) positive and mucicarmine negative. CK19 was strongly positive in the solid tumor islands and variably positive in clear cells. A definitive diagnosis of CGCOT with predominance of clear cells was confirmed. Because both squamous metaplasia and clear-cell components were present in the ameloblastic follicles independent of each other, the presence of abundant calcifications favored the diagnosis of CGCOT with a clear-cell component over that of an ameloblastoma with clear-cell changes. The importance of identifying the histomorphologic features of the 2 entities, ameloblastoma and CGCOT, is highlighted. This appears to be the second case reported in the literature, to the best of our knowledge.

Clear cell odontogenic carcinoma: report of 7 new cases and systematic review of the current knowledge

OBJECTIVE

The goal of this study is to describe 7 cases of clear cell odontogenic carcinoma among a Brazilian population and compare these data with a systematic review of the English-language literature.

STUDY DESIGN

Descriptive statististics were used to compare the clinicopathologic data gathered retrospectively with those compiled from a review. Tumor sections were immunostained for Ki-67, p16, p53, and cytokeratins (CKs) 7, 8, 14, 18, and 19. Log-rank tests were performed for survival analysis.

RESULTS

Most cases occurred in the posterior mandible (5/7, 71.4%), and recurrence was diagnosed in all treated patients. Metastatic disease occurred in 2 patients (28.6%). Tumors were focally positive for CKs 7, 8, 14, and 18 and diffusely positive for CK19, p53, and p16. The mean number of Ki-67-positive cells was 35.2 cells/high-power field. Our systematic review provided evidence that tumor size (P = .046), histologic pattern (P = .034), regional metastasis (P = .001), distant metastasis (P = .001), and local recurrence (P = .05) were of significant prognostic value.

CONCLUSIONS

This study has contributed to improved characterization of clear cell odontogenic carcinoma, which is an aggressive odontogenic malignant neoplasm diagnosed mainly in the posterior mandible of middle-aged women and typically at an advanced stage. Radical surgical procedures remain the gold standard treatment.

Cytomorphology and immunohistochemistry of a recurrent clear cell odontogenic carcinoma with molecular analysis: A case report with review of literature

Clear cell odontogenic carcinoma (CCOC) is a rare, odontogenic tumor of the jaws with mandibular involvement usually present in sixth decade of life with female preponderance. It is classified as a malignant tumor of odontogenic origin in 2005 by the World Health Organization because of its aggressive and destructive growth capacity and potential to metastasize. It needs to be distinguished from other primary and metastatic clear cell tumors of the oral and maxillofacial region. Recently, CCOCs have been noted to harbor a Ewing sarcoma breakpoint region 1 gene RNA-binding protein 1 (EWSR1) and activating transcription factor (ATF) gene translocation. To date, cytologic features of only one case have been reported in the literature. We report an additional case of 55-year-old woman with enlarging mass in the left mandible. This report describes cytologic and immunohistochemical features of CCOC with positive EWSR1 gene rearrangements by fluorescence in situ hybridization (FISH). As diagnosis of CCOC is challenging on fine-needle aspiration, immunohistochemistry and FISH analysis are very useful diagnostic tool in clear cell lesions of mandible.

Clear cell odontogenic carcinomas show EWSR1 rearrangements: a novel finding and a biological link to salivary clear cell carcinomas

Clear cell odontogenic carcinomas (CCOCs) are a rare tumor of the jaws, which have considerable morphologic and immunophenotypic overlap with (hyalinizing) clear cell carcinomas (CCCs) of salivary origin. Fluorescence in situ hybridization for EWSR1 was performed on 12 CCOCs, 14 CCCs, and a control set of other miscellaneous clear cell tumors of the head and neck region. EWSR1 was rearranged in 12/13 (92.3%) CCCs and 5/8 (62.5%) CCOCs. EWSR1 testing failed in 1 CCC and 4 CCOCs. Two cases initially diagnosed as CCOCs that were negative for the EWSR1 translocation, were reclassified as clear cell calcifying epithelial odontogenic tumors. ATF1 involvement was confirmed by fluorescence in situ hybridization analysis in 1 CCOC. In this study, we demonstrate for the first time the EWSR1-ATF1 translocation in a CCOC and demonstrate a concrete link between CCCs and at least a subset of CCOCs.

Intraosseous carcinoma of the jaws: a clinicopathologic review. Part II: Odontogenic carcinomas

This is the second of a 3-part review of the clinicopathologic features of intraosseous carcinoma of the jaws (IOCJ). This part deals with odontogenic carcinomas, rare entities that are difficult to evaluate because of changes in classification/nomenclature, lack of standardized diagnostic criteria, and variable consistency of the existing literature. Endorsing a critical approach, problems are addressed and areas of uncertainty are highlighted. As in part I, we emphasize histopathologic features from a diagnostic point of view and also question the existence of some "distinct" entities.

Clear cell carcinoma and clear cell odontogenic carcinoma: a comparative clinicopathologic and immunohistochemical study

Clear cell carcinoma or hyalinizing clear cell carcinoma (CCC) and clear cell odontogenic carcinoma (CCOC) are rare, low-grade and typically indolent malignancies that can be diagnostically challenging. In this study the clinicopathologic, histologic, and immunohistochemical features of 17 CCCs and 12 CCOCs are examined. The differential diagnosis of clear cell malignancies in the head and neck is discussed. The relationship of CCCs and CCOCs to other clear cell tumors on the basis of their immunohistochemical staining patterns is postulated.

Msx and dlx homeogene expression in epithelial odontogenic tumors

Epithelial odontogenic tumors are rare jaw pathologies that raise clinical diagnosis and prognosis dilemmas notably between ameloblastomas and clear cell odontogenic carcinomas (CCOCs). In line with previous studies, the molecular determinants of tooth development-amelogenin, Msx1, Msx2, Dlx2, Dlx3, Bmp2, and Bmp4-were analyzed by RT-PCR, ISH, and immunolabeling in 12 recurrent ameloblastomas and in one case of CCOC. Although Msx1 expression imitates normal cell differentiation in these tumors, other genes showed a distinct pattern depending on the type of tumor and the tissue involved. In benign ameloblastomas, ISH localized Dlx3 transcripts and inconstantly detected Msx2 transcripts in epithelial cells. In the CCOC, ISH established a lack of both Dlx3 and Msx2 transcripts but allowed identification of the antisense transcript of Msx1, which imitates the same scheme of distribution between mesenchyme and epithelium as in the cup stage of tooth development. Furthermore, while exploring the expression pattern of signal molecules by RT-PCR, Bmp2 was shown to be completely inactivated in the CCOC and irregularly noticeable in ameloblastomas. Bmp4 was always expressed in all the tumors. Based on the established roles of Msx and Dlx transcription factors in dental cell fates, these data suggest that their altered expression is a proposed trail to explain the genesis and/or the progression of odontogenic tumors.

Clear cell odontogenic carcinoma: case report with immunohistochemical findings adding support to the challenging diagnosis

Clear cell odontogenic carcinoma (CCOC) is a rare odontogenic tumor associated with aggressive clinical behavior, metastasis, and low survival. We report a case of CCOC affecting the mandible of a 39-year-old man. The tumor presented a biphasic pattern composed of clear cell nests intermingled with eosinophilic cells and separated by collagenous stroma. Immunoreactivity to cytokeratin (CK), specifically AE1/AE3 and CK 8, 14, 18, and 19 was found, as well as to epithelial membrane antigen (EMA). The tumor cells were negative for S100 protein, CK 13, vimentin, smooth muscle actin, laminin and type IV collagen. Low labeling indices for the proliferation markers Ki-67 and proliferating cell nuclear antigen and to p53 protein might predict a favorable prognosis for the lesion. A surgical resection was performed, followed by adjuvant radiotherapy. A 2-year follow-up has shown no signs of recurrence. The significance of histochemical and immunohistochemical resources in the correct diagnosis of CCOC is analyzed.

Clear cell odontogenic carcinoma of the maxilla: a case report and literature review

BACKGROUND

Clear cell odontogenic carcinoma (CCOC) is a rare tumor of odontogenic origin. It was first described as a clinicopathological entity in 1985, and since then, several case reports have been published.

METHODS

We present a patient with CCOC treated at the University of Florida and review the pertinent literature.

RESULTS

We treated a 52-year-old woman with CCOC of the maxilla. She received a maxillectomy and postoperative radiotherapy (RT). She developed pulmonary metastases 2 years after treatment. She remains alive and asymptomatic 7 years after completing treatment and has not required additional therapy. The literature search yielded 48 other case reports. The median age at presentation was 53 years (mean, 55 years), the female-to-male ratio was 2:1, and the most common site of presentation was the mandible. Three patients presented with submandibular lymphadenopathy. Most patients had a surgical resection (35 patients, 71%); the remainder underwent curettage. Six (12%) patients received postoperative RT. Eighty percent of patients who were initially treated with curettage developed a local recurrence. Local and/or regional recurrences occurred in 34% of patients who underwent surgical resection. Six patients developed distant metastatic disease; the most common site of the metastases was the lung. Seven patients died from or with the disease, and 3 are alive with the disease.

CONCLUSIONS

Clear cell odontogenic carcinoma is a rare tumor of the mandible and maxilla that has the propensity for local destruction and the potential for lymphatic and hematogenous metastases. We recommend radical excision as the primary treatment and that adjuvant RT be added for those who have close or positive margins as well as those with lymph node metastases.

Clear cell odontogenic carcinoma: a comprehensive analysis of treatment strategies

BACKGROUND

Odontogenic neoplasms of predominately clear cells are unusual. They represent a diagnostic dilemma, and as a result, treatment strategies are diverse. Our goal is to present two new cases, summarize reported cases of clear cell odontogenic carcinoma (CCOC), assess potential risk factors for recurrence, and propose definitive surgical and therapeutic strategies.

METHODS

A literature search and analysis was performed. Regression models were used to predict risk factors for recurrence.

RESULTS

Forty-three cases of CCOC were reviewed, including two reported here. The overall rate of recurrent disease was 55%. Local recurrence rates were higher for curettage (80%) than for resection alone (43%). Age (p = .20), sex (p = .28), and tumor site (p = .50) did not predict risk for recurrence.

CONCLUSIONS

CCOC is a potentially aggressive tumor with a tendency for recurrence. Treatment strategies should be directed toward wide surgical resection with confirmation of tumor-free margins. Lymph node dissection and adjuvant radiation therapy should be considered in selected cases.

Metastasising clear cell odontogenic carcinoma: a case report and review of the literature

Primary odontogenic carcinomas are rare and examples which have metastasised are even more uncommon. We describe the first reported case of a clear cell odontogenic carcinoma which metastasised to distant bones, namely the 5th lumbar vertebra and hip, 3 years after initial diagnosis. The initial incisional biopsy was thought to represent a calcifying epithelial odontogenic tumour, but in the subsequent resection the tumour showed a prominent clear cell component admixed with squamous cells showing peripheral palisading, widespread infiltration and necrosis indicating a malignant neoplasm. Radiologically guided biopsy revealed a metastatic lesion in L5 vertebrae and left hip, confirmed by immunohistochemistry. The metastatic lesion had similar appearances to the first biopsy, and diagnosis was confirmed by comparison of histological features, immunohistochemistry and exclusion of a second primary lesion by clinical examination and imaging. The diagnosis of clear cell odontogenic carcinoma is a difficult one to make. The behaviour of these tumours is unpredictable. This case confirms that clear cell odontogenic carcinomas have the potential for distant metastasis and require long-term follow up.

Clear cell odontogenic carcinoma

Clear cell tumours, in the head and neck region, are usually derived from salivary or odontogenic tissues, or may be metastatic. A few clear cells may be present in odontogenic cysts, while, odontogenic neoplasms composed predominantly of clear cells are quite rare. They include calcifying epithelial odontogenic tumours (CEOT), ameloblastoma and odontogenic carcinoma. Clear cell odontogenic tumour (CCOT) has been classified in the last WHO classification as a benign tumour, but it is now recognized as a more sinister lesion and current opinion is that CCOT should be designated as a carcinoma. These tumours are characterized by aggressive growth, recurrences, and metastatic disease. A recent review of the literature has yielded 30 cases of tumours with similar characteristics. These tumours have a peak incidence in the 5th-7th decades, with a female predilection. The anterior portions of the jaws, especially the mandible, are most frequently affected. The aggressive potential of these neoplasms is well documented by the extensive invasion of adjacent tissues, multiple recurrences and regional or distant metastases.

Malignant ameloblastoma: classification, diagnostic, and therapeutic challenges

Ameloblastoma is a benign odontogenic neoplasm of the mandible and maxilla that rarely exhibits malignant behavior. We report the case of an aggressive malignant ameloblastoma of the mandible that presented with an unusual multiphasic, histologic pattern. Initial fine needle aspiration and radiographic findings showed features consistent with a benign, fibro-osseous lesion. However, aggressive growth and the association of enlarged submandibular lymph nodes suggested a more malignant potential. Treatment consisted of an angle-to-angle composite mandibular resection, right modified neck dissection, left functional supraomohyoid neck dissection, and anterior chin skin resection with iliac crest osteocutaneous free flap reconstruction. Microscopic evaluation showed primarily malignant ameloblastoma without cellular atypia and extensive fields of fibro-osseous tissue with smaller fields of clear cell odontogenic tumor. This multiphasic, histologic arrangement may explain the perplexing preoperative microscopic diagnosis, suggesting a benign fibro-osseous lesion. Of the lymph nodes analyzed, one from the right submandibular triangle exhibited metastatic, benign-appearing ameloblastoma without fibro-osseous or clear cell features. The absence of cellular features of malignancy in the tumor mass and lymph node metastasis suggest that the lesion should be classified as malignant ameloblastoma rather than ameloblastic carcinoma or odontogenic carcinoma. A malignant ameloblastoma with all 3 of the aforementioned microscopic features has not been previously reported. We review the classification of epithelial odontogenic malignancies. Lesions showing multiphasic patterns can create diagnostic dilemmas and may require extensive surgical sampling and/or removal to establish an accurate diagnosis.

Clear cell odontogenic carcinoma. Report of two cases and review of the literature

This study reviews the literature and reports on the morphologic and immunophenotypic features of 2 clear cell odontogenic carcinomas occurring in the mandible of elderly women, showing extensive infiltration into adjacent tissues. The tumor cells were large, with clear cytoplasm, and arranged in irregular sheets. Some of the latter demonstrated a peripheral rim of cells with eosinophilic cytoplasm or included duct-like structures. There was no evidence of ameloblastic differentiation. Most cells contained glycogen granules and were immunoreactive for cytokeratins and epithelial membrane antigen. In the differential diagnosis other clear cell odontogenic, salivary gland, and metastatic tumors should be considered. Both cases were treated with surgical excision, and the patients are free of disease after 3 and 5 years, respectively. In the literature, however, variable behavior of these tumors has been reported, including recurrence and metastases. It is recommended that terms such as clear cell ameloblastoma and clear cell odontogenic tumor not be used to describe such tumors.

Radiographic manifestation of clear cell odontogenic tumor

Clear cell odontogenic tumors are uncommon, only 20 cases having been reported in the literature. We report a case that presented with unique radiographic manifestations over a period of 12 years; no similar case has been reported to date. Documentation of the malignant nature of the condition and of the range of clinical and radiographic manifestations with which this neoplasm can present provides useful insight into its pathogenesis and progression. Early and timely recognition of the lesion, histopathologic examination, and aggressive interventional procedures are in order to successfully treat this condition and prevent a potentially fatal outcome.

Expression of E-cadherin and alpha-catenin in epithelial odontogenic tumors: an immunohistochemical study

To clarify the possible role of cell adhesion in epithelial odontogenic tumors, expression of E-cadherin and alpha-catenin was examined by an immunohistochemical method. These molecules showed pericellular distribution in epithelial cells of the tooth germ and its derived tumors. In ameloblastomas, E-cadherin and alpha-catenin were expressed strongly in central polyhedral cells and slightly in peripheral columnar cells. These features resembled those of epithelial components in the tooth germ tissues, retaining cytodifferentiation of odontogenic epithelium. Expression of the molecules in the variants of ameloblastomas showed loss in the keratinizing areas and reduction in the granular cell clusters, suggesting terminal differentiation of the tumor cells. Calcifying epithelial odontogenic tumors and a clear cell odontogenic tumor preserved E-cadherin and alpha-catenin expression without a specific feature for histogenesis or cytodifferentiation. One case of two malignant ameloblastomas showed prominent reduction in expression of E-cadherin and alpha-catenin.

Clear cell odontogenic tumor in the mandible: report of a case with an immunohistochemical study of epithelial cell markers

A rare case of clear cell odontogenic tumor is presented with an immunohistochemical study using epithelial cell markers. A 35-year-old Japanese man was admitted with a complaint of painless swelling in the anterior region of his mandible. Radiological examination showed a relatively well-defined multilocular radiolucency with root resorption of the adjacent teeth. Despite a subtotal mandibulectomy, the tumor recurred three times. Histologically, the tumor was composed of proliferating clear cells and infiltrated through the cancellous bone. Histochemical and ultrastructural analyses detected cytoplasmic glycogen granules in the clear cells. They showed immunoreactivities for cytokeratin 8, 13 and 19, filaggrin and anti-ameloblastoma antibodies, suggesting an odontogenic epithelial origin.

Clear cell odontogenic carcinoma: A case report and literature review of odontogenic tumors with clear cells

Clear cell odontogenic carcinomas are uncommon epithelial neoplasms that have metastatic potential. We describe such a tumor in a 67-year-old Japanese man with a well-defined, unilocular radiolucent area in the mandible. The tumor was enucleated and has not recurred or metastasized 3 years after surgery. Histologically, the tumor was composed of a predominant clear cell area and a plexiform ameloblastic pattern. The latter was located at the periphery of the tumor. In the English literature, 19 cases of clear cell odontogenic carcinoma, clear cell odontogenic tumor, and clear cell ameloblastoma have been reported. The mean age of the patients at diagnosis was 56.4 years and the gender ratio (M:F) was 8:11. Fourteen tumors were located in the mandible and 5 in the maxilla. Recurrence or metastasis occurred in approximately one half of these patients, and five of the patients died of their disease. More than one half recurrent or metastatic tumors contained palisading clear cells.

Clear cell odontogenic tumour: a case with induction of dentin-like structures?

A case of clear cell odontogenic tumour, which occurred centrally in the mandible of a 56-year-old Japanese woman, is reported with its histochemical, immunohistochemical and ultrastructural findings. Histologically, the tumour nests were composed of large glycogen-rich clear cells and small non-clear polygonal cells and were separated by thin mature fibrous connective tissue septae. Immunohistochemically, both types of tumour cells showed positive expression of various cytokeratins, in particular cytokeratin 19, and of epithelial membrane antigen. Eosinophilic hyaline deposits and possible dentin-like structures were occasionally formed in contact with the epithelial nests and are regarded as indicative of the epithelial-mesenchymal inductive capacity of this tumour. The aggressive nature of the present tumour was assumed through its invasive growth pattern and occasional mitotic figures. Although it was diagnosed as clear cell odontogenic tumour according to the present WHO classification, the patient must be followed carefully because of its probable malignant nature.

Clear cell odontogenic carcinoma in the mandible: histochemical and immunohistochemical observations with a review of the literature

A rare case of clear cell odontogenic carcinoma was investigated using histochemical and immunohistochemical methods. The tumor occurred in the anterior mandible of a 69-year-old Japanese man. Histologically, the tumor was composed mostly of large clear cells and squamous cells. Columnar-shaped cells with basophilic nuclei polarized away from the basement membrane were observed at the periphery of the tumor foci. The tumor cells had aggressively invaded muscle and perineural tissues. The tumor cells were positive for PAS staining. Immunohistochemically, tumor cells reacted positively to keratin, cytokeratin19, epithelial membrane antigen, and S-100 protein. The tumor was diagnosed as a clear cell odontogenic carcinoma. Its characteristics are discussed in term of its histopathological, histochemical and immunohistochemical features.

Clear-cell ameloblastoma (clear-cell odontogenic carcinoma): report of a case

Clear-cell ameloblastoma (clear-cell odontogenic carcinoma) is an uncommon odontogenic epithelial neoplasm. We report a case of a well-circumscribed 2 cm radiolucent lesion of the anterior mandible in a 30-year-old woman; this tumor was curetted. The first recurrence (at 5-year follow-up) was treated by aggressive curettage, and in the second recurrence a block resection was performed. However, 2 years after the resection was performed, the tumor recurred for a third time as an extraosseous gingival tumor, and 6 months later a recurrence was noted involving only alveolar mucosa.

Clear cell ameloblastoma or odontogenic carcinoma. A case report

An ameloblastoma of the right maxilla with a biphasic pattern of folicular ameloblastoma and clear cells, with an aggressive clinical behaviour in a 71-year-old male is reported. A literature review of clear cell ameloblastomas is made, focussing the discussion on the convenience of considering this type of ameloblastoma to be a low-grade odontogenic carcinoma.

Clear cell odontogenic carcinoma. Report of a case with lymph node and pulmonary metastases

The authors present a case of a rare type of odontogenic tumour, recently described as "clear cell odontogenic tumour". The patient died 5 years after the initial diagnosis with lymph node and diffuse pulmonary metastases. This fact can support the view that this tumour, histologically characterised by the presence of cells with a clear cytoplasm, can behave in an aggressive way and has true metastatic potential, despite the absence of malignant cellular features.

Clear cell variant of calcifying epithelial odontogenic tumor: case report and review of the literature

The calcifying epithelial odontogenic tumor (CEOT) is a rare benign odontogenic neoplasm which was first described by Pindborg in 1955 and accounts for less than 1% of all odontogenic lesions. Recently, a clear cell variant of CEOT has been identified with only eight well-documented cases in the literature. We present an additional case of clear cell CEOT of the mandible and review the salient clinical, radiologic, and histopathologic features of this entity and CEOTs in general. The differential diagnosis of clear cell tumors in the mandible includes: clear cell odontogenic tumor, clear cell ameloblastoma (odontogenic carcinoma), metastatic clear cell adenocarcinoma, primary intraosseous mucoepidermoid carcinoma, acinic cell carcinoma, epithelial-myoepithelial carcinoma, clear cell salivary gland tumors, and clear cell variant of squamous cell carcinoma. Because of the belief that clear cell odontogenic tumors are locally aggressive neoplasms, definitive resection of the entire mass with tumor-free surgical margins and long-term follow-up are recommended.

On the differential diagnosis of clear cell tumours of the head and neck

Clear cell tumours, both benign and malignant, derive from a diverse group of epithelial cell types including renal epithelium, keratinising epithelium, cutaneous adnexa, salivary glands, odontogenic epithelium, melanocytes and even mesenchymally derived cells of adipose and tendon sheath. In the head and neck, clear cell tumours represent a singular challenge to the pathologist since the classic morphological features of malignant neoplasia exemplified by cytological atypia are frequently absent in malignant clear cell variants, thereby excluding reliance on this histopathological hallmark for the establishment of a diagnosis. The differential diagnosis of both benign and malignant clear cell tumours must take into account patterns of growth as well as the phenotype of accompanying cell populations when attempting to arrive at a definitive histological diagnosis. In this review article, the histopathology of head and neck tumours that harbour significant clear cell populations will be compared and contrasted.

Clear cell odontogenic carcinoma. A case report with massive invasion of neighboring organs and lymph node metastasis

Clear cell odontogenic carcinoma is a rare and unusual tumor that occurs in the jaws. This tumor is generally considered to be of a low grade of malignancy. We describe a patient with a huge clear cell odontogenic carcinoma that originated in the mandible and exhibited massive invasion into the adjacent tissues and metastases to the submandibular lymph nodes. The ultrastructural and immunohistochemical details are described.

Human ameloblastoma tumors express the amelogenin gene

Instructive signals are responsible for the regulation of the expression of gene products characteristic of many cell lineages during normal development and potentially during neoplasia. The odontogenic origin of ameloblastomas is based largely on the similarity in histologic appearance between the tumor and the developing tooth organ. A pathognomonic pattern for odontogenic tissue-specific gene expression in ameloblastomas has not been previously shown. In these studies, the gene expression parameters for human ameloblastomas have been characterized with the techniques of messenger RNA phenotyping in combination with Northern and in situ hybridization analysis of messenger RNA. The results of these studies confirm that amelogenin, a gene transcribed solely by differentiated ameloblasts, was expressed by epithelial cells from human ameloblastomas. This observation suggests that the instructive signals required for ameloblast differentiation are shared during normal development and tumorigenesis of odontogenic epithelium.

Clear cell calcifying epithelial odontogenic tumor. A case report

Clear cell variants of odontogenic tumors are rare. A case of clear cell calcifying epithelial odontogenic tumor of the mandible in a 38-year-old Caucasian male is described. This case is compared to 8 previously reported cases. The origin of clear cells in odontogenic tumors is still unknown. En bloc resection of the tumor is recommended.

Clear cell odontogenic carcinoma: report of three cases with pulmonary and lymph node metastases

Three cases of a newly described rare odontogenic tumor are reported. One patient died with pulmonary metastases, one had an associated odontogenic cyst and one exhibited regional lymph node metastasis. The cases lend support to the odontogenic origin and metastatic capability of the clear cell odontogenic tumor. The authors recommend aggressive therapy and believe that the tumor should be considered a clear cell odontogenic carcinoma.

In situ hybridization analysis of keratin gene expression in human ameloblastomas

Complementary DNA (cDNA) clones corresponding to the 55 kDa (K 14) and 59 kDa (K 10) keratins were used as probes for in situ hybridization analysis for the expression of keratin genes in human ameloblastomas and in oral mucosa. Transcripts for either the K 14 keratin or the K 10 keratin were restricted in their spatial distribution within stratified epithelia consistent with the stage of differentiation of the keratinocyte: the K 14 keratin gene transcript was restricted to the basal cell layers of the mucosa, while the K 10 keratin transcript was expressed predominantly in suprabasal cells, within the granular and prickle layers. In contrast, only the K 14 keratin transcript could be identified within the epithelial cells of human ameloblastomas. The differentiation-specific keratin transcript (K 10) was not present at detectable levels in this type of odontogenic tumors. In an atypical, infiltrating ameloblastoma, neither the K 10 nor the K 14 transcript could be identified. Granular cells within one ameloblastoma expressed the K 14 transcript. A detailed examination of the pattern of gene expression in these unique tumors may lead to a better understanding of their pathogenesis.

Clear cell odontogenic tumor--a new histologic variant with aggressive potential

This report delineates the clinical and laboratory findings for a previously unreported neoplasm of putative odontogenic origin. We describe the clinical, radiographic, operative, histologic, histochemical, and ultrastructural findings of the tumor in three women. All lesions were centrally located in the jaw bones, were expansile, and, except for mobile teeth and/or jaw enlargement, exhibited few symptoms. Radiographically, there was bone and tooth destruction resulting in poorly delineated margins. Microscopically, the tumors were nearly identical in that they consisted primarily of large sheets and islands of uniform vacuolated and clear cells without evidence of amyloid deposition, calcification, or glandular differentiation. One of the lesions recurred 1 1/2 years after removal without evidence of metastasis. The results, based only on these cases, suggest that this is a locally aggressive neoplasm of odontogenic origin. Casual microscopic examination of this rare neoplasm could result in misdiagnosis as a metastatic clear cell neoplasm, especially renal cell carcinoma.