Immunocytochemical demonstration of intermediate filaments in a granular cell ameloblastoma

Recurrent ameloblastoma of the mandible with unusual granular cell component

Ameloblastomas can present in various clinical and histomorphologic patterns. The granular cell variant accounts for only 3.5% to 5% of ameloblastomas. The aim of this case report is to present an example of ameloblastoma with unusual granular cell component, affecting a 63-year-old woman, in which both the inner and peripheral layers of follicles composed exclusively by eosinophilic granular cells. Assessment of the immunohistochemical and histochemical profile of the lesion was performed and the challenges of such a diagnosis were also addressed.

Massive granular cell ameloblastoma with dural extension and atypical morphology

Ameloblastomas are rare histologically benign, locally aggressive tumors arising from the oral ectoderm that occasionally reach a gigantic size. Giant ameloblastomas are a rarity these days with the advent of panoramic radiography in routine dental practice. Furthermore, the granular cell variant is an uncommon histological subtype of ameloblastoma where the central stellate reticulum like cells in tumor follicles is replaced by granular cells. Although granular cell ameloblastoma (GCA) is considered to be a destructive tumor with a high recurrence rate, the significance of granular cells in predicting its biologic behavior is debatable. However, we present a rare case of giant GCA of remarkable histomorphology showing extensive craniofacial involvement and dural extension that rendered a good prognosis following treatment.

Granular cell ameloblastoma: enigmatic cells in an unusual neoplasm

An unusual granular variant of ameloblastoma presenting as a mandibular mass in a 43-year-old woman is described. These visually striking tumors display unusual and inconsistent immunohistochemical staining patterns although differential diagnosis from other granular cell lesions of the head and neck is usually not problematic.

Investigation of basement membrane proteins in a case of granular cell ameloblastoma

Granular cell ameloblastoma is a rare, benign neoplasm of the odontogenic epithelium. A case of massive granular cell ameloblastoma in a 44-year-old Thai female is reported. Histopathological features displayed a follicular type of ameloblastoma with an accumulation of granular cells residing within the tumor follicles. After treatment by partial mandibulectomy, the patient showed a good prognosis without recurrence in a 2-year follow-up. To characterize the granular cells in ameloblastoma, we examined the expression of basement membrane (BM) proteins, including collagen type IV, laminins 1 and 5 and fibronectin using immunohistochemistry. Except for the granular cells, the tumor cells demonstrated a similar expression of BM proteins compared to follicular and plexiform ameloblastomas in our previous study, whereas the granular cells showed strong positivity to laminins 1 and 5 and fibronectin. The increased fibronectin expression in granular cells suggests a possibility of age-related transformation of granular cells in ameloblastoma.

Cytokeratins expression of constituting cells in ameloblastoma

The purposes of this study were to investigate the distribution of cytokeratins in the different tissue types of ameloblastoma and to discuss the histogenesis of this tumor. CK19 and CK8, which are markers for odontogenic epithelium, reacted positively to the constituting cells in all types of ameloblastoma. This suggests that all types of ameloblastoma derive from odontogenic epithelium. However, the desmoplastic type diminished the odontogenic characteristics because the basal cells are negative to CK19. Immunoreactions of five kinds of cytokeratin revealed similar results in plexiform, follicular, acanthomatous, and granular cell types. The plexiform type is probably the original type of ameloblastoma; the other types have the characteristics of squamous epithelium, and the follicular, acanthomatous, and granular cell types can develop due to the differentiation of cells of the plexiform type into squamous epithelium.

Immunohistochemical expression of neural tissue markers (neuron-specific enolase, glial fibrillary acidic protein, S100 protein) in ameloblastic fibrodentinoma: a comparative study with ameloblastic fibroma

Formalin-fixed paraffin-embedded sections of three cases of ameloblastic fibrodentinoma (AFD) were studied by the avidin-biotin-peroxidase complex method using antibodies against neuron-specific enolase (NSE), glial fibrillary acidic protein (GFAP) and S100 protein and the results were compared with those in ameloblastic fibroma (AF). A striking histopathological characteristic of AFD was the formation of abortive dentin with various degrees of maturation at the epithelial-mesenchymal tissue interface. Central cells of enamel organ-like epithelia with various stages of abortive dentin induction in AFD were generally positive for NSE. Dental lamina-like epithelial cells also showed positive staining in some areas. No cells were positive for NSE in AF. Positive staining for GFAP was observed in the juxta-epithelial mesenchymal tissue of the formation stage of immature dentin with various numbers of entrapped cells in AFD, but GFAP staining was negative in other mesenchymal and epithelial tissues at other stages. In AF, no GFAP-positive cells were found. There were a few S100 protein-positive cells found in the foci of epithelial components in both AFD and AF. Mesenchymal cells showing a dendritic or spindle shape were positive for S100 protein in some areas of AFD and AF. Although such cells in the mesenchymal component of pigmented AFD were more numerous than in non-pigmented AFD and AF, their distribution pattern in the former condition was basically similar to that in the latter. Although the present results, obtained from conventional immunohistochemical procedures, do not directly reflect the expression of neural crest-derived cells in the dentinogenesis of AFD, such results do not disprove the possibility of the expression of neural proteins probably related to neural crest-derived cells in dentinogenesis under certain pathologic conditions in odontogenic mixed tumors. Such a phenomenon may also occur during dentinogenesis in other odontogenic mixed tumors and in normal tooth differentiation, but at an undetectable level.

Aberrant gene expression in epithelial cells of mixed odontogenic tumors

Comparative investigations of odontogenic cells in normally forming teeth and tumors may provide insights into the mechanisms of the differentiation process. The present study is devoted to late phenotypic markers of ameloblast and odontoblast cells, i.e., proteins involved in biomineralization. The in situ expression of amelogenins, keratins, collagens type III and IV, vimentin, fibronectin, osteonectin, and osteocalcin was performed on normal and tumor odontogenic human cells. The pattern of protein expression showed some similarities between ameloblasts and odontoblasts present in normally developing human teeth and cells present in neoplastic tissues of ameloblastic fibroma, ameloblastic fibro-odontomas, and complex odontomas. Amelogenins (for ameloblasts) and osteocalcin (for odontoblasts) were detected in cells with well-organized enamel and dentin, respectively. In contrast, "mixed" cells located in epithelial zones of mixed odontogenic tumors co-expressed amelogenins and osteocalcin, as shown by immunostaining. The presence of osteocalcin transcripts was also demonstrated by in situ hybridization in these cells. Keratins and vimentin were detected in the same epithelial zones. Tumor epithelial cells were associated with various amounts of polymorphic matrix (amelogenin- and osteocalcin-immunoreactive), depending on the types of mixed tumors. No osteocalcin labeling was found in epithelial tumors. This study confirms that the differentiation of normal and tumor odontogenic cells is accompanied by the expression of some common molecules. Furthermore, the gene products present in normal mesenchymal cells were also shown in odontogenic tumor epithelium. These data may be related to a tumor-specific overexpression of the corresponding genes transcribed at an undetectable level during normal development and/or to an epithelial-mesenchymal transition proposed to occur during normal root formation. A plausible explanation for the results is that the odontogenic tumor epithelial cells are recapitulating genetic programs expressed during normal odontogenesis, but the tumor cells demonstrate abnormal expression patterns for these genes.

Granular cell ameloblastoma. An immunocytochemical study

Granular cell ameloblastoma is characterized by nests of large, eosinophilic granular cells. These latter have long been the subject of debate. Two cases of granular cell ameloblastomas have been immunocytochemically stained with a panel of antibodies against human mitochondria, S-100 protein, CD 68, low molecular weight cytokeratins, chromogranin, laminin, vimentin, PCNA, bcl-2 and p-53. Granular cells exhibited a membranous positivity with cytokeratins while the non granular cells of the same tumors showed a diffuse cytoplasmic reactivity. Moreover, granular cells showed marked cytoplasmic positivity with CD68 antiserum only while human mitochondria, as well as S-100 protein antisera, were consistently negative. PCNA, bcl-2 and p-53 did not stain the granular cells. These results allow easy distinction of granular cell ameloblastomas from similar tumors exhibiting granular cell changes and indicate that the granularity in ameloblastoma cells is consequent to lysosomal overload.

Maintenance of cell-type-specific cytoskeletal character in epithelial cells out of epithelial context: cytokeratins and other cytoskeletal proteins in the rests of Malassez of the periodontal ligament

We have determined the patterns of synthesis of cytokeratins and other epithelial marker proteins in the "rests of Malassez" of the periodontium of rabbits and humans, by immunofluorescence microscopy of cryosections prepared from fixed and decalcified rabbit teeth with attached ligament or from manually isolated human periodontal ligaments. Proteins of the major cell structures characterizing epithelial differentiation are present in Malassez cells: a complex set of cytokeratins as well as desmosomal, hemidesmosomal and basal lamina proteins. In addition, we have shown these cytoskeletal and extracellular matrix structures by electron microscopy. The cytokeratin complement of Malassez cells was found to be highly complex, as 8 of the total of 20 known epithelial cytokeratins were detected (nos. 5, 7, 8, 14, 15, 17, 18, 19). This pattern, together with the presence of the desmosomal cadherins Dsg2 and Dsc2 and the cytoplasmic desmosome plaque-associated protein plakophilin 1, indicates that the cells of the rests of Malassez are derived from the basal cell layer of a stratified squamous epithelium rather than from simple epithelial or neuroendocrine epithelial cells. Our observations show that Malassez cells retain the major characteristics of epithelial cells throughout their differentiation from the root sheath epithelium into the rests of Malassez, even though the surface location and the polar tissue architecture that typify epithelial are lost during this process. From this study we further conclude that the specific cytoskeletal complement of the Malassez cells represents an intrinsic gene expression program that neither depends on nor causes the formation of a stratified epithelium. We also compare the specific cytoskeletal features of Malassez cells with those of other persisting epithelial residues and discuss the potential value of these findings in relation to the histogenesis and diagnostic classification of dental and periodontal cysts and tumors.

Ameloblastoma: biological profile of 3677 cases

Available literature on ameloblastoma of the jaw was reviewed, including publications from 1960 to 1993, and compared to the latest larger review, published by Small and Waldron in 1955. The average age of patients with ameloblastoma is 36 years. In developing countries ameloblastomas occur in younger patients. Men and women are equally affected. Women are 4 years younger than men when ameloblastomas first occur, and the tumours appear to be larger in females. Dominant clinical symptoms such as painless swelling and slow growth are non-characteristic. The ratio of ameloblastoma of the mandible to maxilla is 5 to 1. Ameloblastomas of the mandible occur 12 years earlier than those of the maxilla. Ameloblastomas occur most frequently in the molar region of the mandible. In Blacks, ameloblastomas occur more frequently in the anterior region of the jaws. Radiologically, 50% of ameloblastomas appear as multilocular radiolucent lesions with sharp delineation. Histologically, one-third are plexiform, one-third follicular; other variants such as acanthomatous ameloblastoma occur in older patients. Two percent of ameloblastomas are peripheral tumours. Unicystic ameloblastomas occurring in younger patients have been found in 6%. Detailed data on 345 patients with ameloblastoma were evaluated for clarification of therapeutic approaches. Chemotherapy and radiation seem to be contraindicated. Ameloblastomas of the maxilla should be treated as radically as possible, ameloblastomas of the mandible should also be treated radically. However, ameloblastomas which radiologically appear as unilocular lesions may be treated conservatively (enucleation, curettage), whenever all areas of the cystic lumen are controllable intraoperatively. Unicystic ameloblastomas occurring in patients 15 years younger than those with multisystic ameloblastoma may be treated conservatively except in cases with invasion of epithelium into the cyst wall. Different recurrence rates have been found for histological variants of the ameloblastoma. Follicular ameloblastomas appear to recur more often than the plexiform type. Unicystic ameloblastomas reveal lower recurrence rates than "non-unicystic" ameloblastomas. The peripheral type of ameloblastoma may be excised, since conservative therapy results in low recurrence rates. Postoperative follow-up is most important in the therapy of ameloblastoma, because more than 50% of all recurrences occur within 5 years postoperatively.

An immunohistochemical study of odontogenic mixed tumours

Five cases of odontogenic mixed tumour comprising of an ameloblastic fibroma, an adenomatoid odontogenic tumour, an odonto-ameloblastoma and two ameloblastic fibro-odontomas were immunohistochemically investigated. Odontogenic epithelial cells were fully positive for cytokeratin detected by antibody KL-1, although there were some differences in its intensity. In contrast, for tenascin, only immature dental papilla-like mesenchymal tissue, especially around the dental lamina-like odontogenic epithelium, was positive, while the myxomatous area and connective tissue were negative. Positive vimentin staining was observed in some areas of immature dental papilla-like cells as well as the basement membrane of odontogenic epithelium in the ameloblastic fibroma, suggesting that this tumour had developed at the early stage of tooth formation. Proliferating nuclear cell antigen-positive cells were generally rarely seen, but were frequently observed in epithelial cells of the ameloblastic fibroma and odonto-ameloblastoma. These observations suggest that tumour cells in each odontogenic mixed tumour possess characteristic proteins associated with proliferation potential and that ameloblastic fibroma and odonto-ameloblastoma have higher proliferation potential among the tumours examined.

Cytokeratin expression in normal and (pre)malignant head and neck epithelia: an overview

Intermediate filament proteins (IFPs) are important markers of tissue differentiation and have been receiving increasing interest, in particular, through their applicability in the characterization of malignant tumors. Cytokeratins (Cks) are a family of IFPs that are typically specific for epithelial cells. They are expressed in certain combinations depending on the type of epithelium and the degree of differentiation. This review presents a critical analysis of the available data on Ck expression in normal and (pre) neoplastic epithelia of the head and neck region. Special attention is paid to technical and cell biologic pitfalls, which can lead to false-negative or false-positive data. It appears that only a limited fraction of the reported data contributes substantially to our knowledge of IFP expression in head and neck cancer because of the use of ill-defined, often formalin-fixed and paraffin-embedded, tissue specimens, and the application of limited panels of monoclonal antibodies. It is concluded that the use of immunocytohistochemistry is promising for the differential diagnosis of head and neck tumors and contributes to our knowledge on their biologic behavior. However, documentations of more complete Ck expression patterns of normal and (pre)malignant epithelium are required, together with their correlation to clinical parameters.

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.

Calcifying odontogenic cysts: co-expression of intermediate filament proteins, and immunohistochemical distribution of keratins, involucrin, and filaggrin

The epithelia lining the cyst of five cases of calcifying odontogenic cyst (COC) were evaluated immunohistochemically with the use of monoclonal antibodies (MoAb's) against keratin (PKK1, KL1, K4.62, K8.12) and vimentin, and polyclonal antisera agonist involucrin and filaggrin. Epithelial lining of COC was classified into 1) thin squamous-cell epithelium, 2) ameloblastoma-like, and 3) thin or 4) thick calcifying odontogenic epithelium. Foci consisting of ghost cells or calcified cells were categorized as calcifying epithelial odontogenic tumor (CEOT). Thin squamous-cell epithelium reacted with PKK1, KL1, K4.62, K8.12, and anti-vimentin MoAb's, thus demonstrating the co-expression of keratin and vimentin. Ameloblastoma-like cells showed positive staining with PKK1, KL1, and sometimes with anti-vimentin. Thick calcifying odontogenic epithelial lining showed stratification of cell layers, and the most strikingly reactive zone was the upper intermediate layer, which showed the presence of keratin, involucrin, and a small amount of filaggrin. Cells of this layer might be the most differentiated type of cells in COC. Undifferentiated odontogenic cells of COC masses were characterized by co-expression of keratin and vimentin, and by the absence of involucrin and filaggrin. All ghost cells were devoid of any immunostaining except for filaggrin, which was rarely positive, but eosinophilic or basophilic cells surrounding the ghost cells showed intense staining for all keratin proteins except vimentin.

Immunoreactivity of granular cell lesions of skin, mucosa, and jaw

Granular cell lesions from many different sites share similar light and electron microscopic features. Immunologically, however, these lesions do not appear to be a homogenous group. This study determines the extent of immunologic heterogeneity of granular cell lesions from a wide variety of sites in skin, mucosa, and jaw. Thirty-one granular cell lesions (26 granular cell tumors [GCT] and five other granular cell lesions) from 18 different sites were evaluated immunohistochemically for keratins, vimentin, desmin, muscle actin, ACT, HLA-DR, and S-100 protein. Paraffin-embedded sections were utilized with an avidin-biotin complex immunoperoxidase technique. Except for ameloblastomas, all lesions were negative for keratin and positive for vimentin. All lesions were negative for desmin and actin. Positive ACT reactivity was found in one of seven GCT of tongue, a colonic lesion, a nose lesion, and a granular cell ameloblastic fibroma. All lesions were positive for HLA-DR except a few in which fixation appeared inadequate. S-100 immunoreactivity was found in all lesions except the congenital epulis, a GCT of the skin of the nose, a colonic lesion, and the odontogenic tumors. The antigenic profile of GCT of skin and mucosa is consistent with Schwann cell origin. However, some GCT and other granular cell lesions appear to be derived from macrophages, epithelial cells, or other cells. The expression of HLA-DR by granular cells is believed to be unrelated to cellular origin but rather to some common immunologic function.

Distribution of intermediate-filament proteins in the human enamel organ: unusually complex pattern of coexpression of cytokeratin polypeptides and vimentin

We applied immunohistochemical techniques and gel electrophoresis to examine the distribution of intermediate filaments in human fetal oral epithelium and the epithelia of the human enamel organ. Both methods demonstrated that human enamel epithelia contain cytokeratins 5, 14, and 17, which are typical of the basal cells of stratified epithelia, as well as smaller quantities of cytokeratins 7, 8, 19, and in trace amounts 18, which are characteristic components of simple epithelial cells. In the external enamel epithelium and stellate-reticulum cells, most of these components appeared to be simultaneously expressed. In contrast, the parental oral epithelium was negative for cytokeratin 7, thus indicating possible "neoexpression" during the course of tooth formation. Immunohistochemical procedures using various monoclonal antibodies against vimentin revealed the transient coexpression of vimentin and cytokeratins in the external enamel epithelium and in stellate-reticulum cells during enamel development. The significance of the coexpression of cytokeratins and vimentin is discussed in relation to previous findings obtained in other normal tissues and in the light of the functional processes characteristic of these epithelia.

Patterns of expression of intermediate filaments in ameloblastoma and human fetal tooth germ

Monoclonal antibodies (Mab) were used to study the expression of cytokeratins and vimentin in various histological types of ameloblastoma and in human fetal tooth germ. The ameloblastoma and the tooth germ epithelia showed characteristics of both simple glandular and stratified squamous epithelial cells. Cytokeratin No. 18 was detected focally in most ameloblastomas studied but not in fetal odontogenic epithelia. Cytokeratins Nos. 8 and 19 were expressed in all epithelial elements of ameloblastomas and tooth germs. Only two tumors showed focally characteristics of keratinizing epithelia also seen in dental lamina but not in the enamel organ. All tumors except the granular cell ameloblastoma showed a variable coexpression of vimentin and cytokeratins in their neoplastic epithelia. A similar coexpression was detected in the stellate reticulum cells of the developing tooth. Ameloblastoma and human tooth germ epithelia share complex pattern of cytokeratin polypeptides together with coexpression of vimentin. The results strongly support the theory that ameloblastomas are of odontogenic origin and not direct derivatives of basal cells of oral epithelium or epidermis.

Granular cell odontogenic cyst: a unicystic ameloblastoma with late recurrence as follicular ameloblastoma

This report is a follow-up of the original case of granular cell odontogenic cyst described by Gold and Christ in 1970. The lesion, originally treated by enucleation in 1965, recurred 18 years later as a follicular ameloblastoma with prominent plexiform and acanthomatous histologic patterns. No histologic evidence of granular cells was noted in the recurrent lesion. The recurrent ameloblastoma was treated by marginal resection of the body of the mandible and immediate reconstruction with an iliac bone graft. The anatomic restoration was excellent, and there is no recurrence 5 years postoperatively. This case supports the view that the granular cell odontogenic cyst is a unicystic (monocystic) granular cell ameloblastoma, and that the presence of granular cells in ameloblastoma is not a permanent feature and may be of little value as a prognostic indicator of aggressiveness.

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.

Ameloblastic fibroma: growth potentiality of odontogenic epithelium and coexpression of intermediate filament proteins in fibromatous cells

Four cases of ameloblastic fibroma are described immunohistochemically in terms of intermediate-sized proteins in both epithelial and mesodermal components. Keratin proteins were demonstrated by polyclonal anti-keratin antiserum (TK: detecting 41-65 kDa keratins) and 2 monoclonal antibodies to keratin (KL1: 55-57 kDa, PKK1: 44, 46, 52 and 54 kDa), and monoclonal antibodies to vimentin and desmin. Two types of odontogenic epithelial tumour cells were discriminated: undifferentiated odontogenic cells and common ameloblastoma cells. Keratin expression was found to be stronger in undifferentiated cells than in the ameloblastoma cells. Undifferentiated cells were PAS-positive, while ameloblastoma cells were negative. Fibroma cells were strongly positive for vimentin, and negative for desmin. Keratin proteins were also expressed slightly. Thus, coexpression of keratin and vimentin was seen in fibroma cells. Histogenesis is discussed from the standpoint of the distribution patterns of keratin and vimentin, as well as with respect to the histopathology.