Experimentally induced ameloblastomas: a critical review

This article reviews the experimental induction of ameloblastomas with emphasis on the acceptability of the induced tumors as being truly equivalent to ameloblastomas in humans. Attempts to induce odontogenic tumors in experimental animals have been made sporadically since the early 1960's but the yield of ameloblastomas has been low. Tumors resembling ameloblastomas, but not completely typical histologically and apparently lacking the invasive qualities of ameloblastoma, have been produced in mice using polyoma virus. However, the most typical ameloblastomas have been those induced in opossums, using ethylnitrosourea. Consequently, it is recommended that this model be used in any further attempts to produce ameloblastomas experimentally.     

Infrequent clinicopathological findings in 108 ameloblastomas

One hundred and eight ameloblastomas diagnosed in a rural black Africa population were analysed for clinicopathologic findings other than those classically described. One patient had a polycystic ameloblastoma adjacent to an ameloblastic fibroma. Two other polycystic ameloblastomas showed aneurysmal bone cyst formation and one mandibular tumour was diagnosed as a keratoameloblastoma. Microscopic changes resembling an adenomatoid odontogenic tumour were present in association with two unicystic ameloblastomas and a HPV18-positive verrucous lesion occurred in the lining of a cystic space of a polycystic ameloblastoma. Two ameloblastomas contained eosinophilic granules in all tumor cells and melanocytes were diffusely present in another. One case exhibited a focus of mucous cell metaplasia. Two polycystic ameloblastomas showed diffuse interstitial ossification. One mandibular tumor was diagnosed as a desmoplastic ameloblastoma and another as an odontoameloblastoma. This study demonstrated that although ameloblastomas are regarded as a fairly homogeneous group of neoplasms, detailed investigations prove clinicopathologic diversity in a significant number of lesions.     

Ameloblastomas in cats: a critical evaluation of the literature and the addition of one example

Gardner DG: Ameloblastomas in cats: a critical evaluation of the literature and the addition of one example. J Oral Pathol Med 1998; 27: 39–42. © Munks-gaard, 1998.
The English language literature on feline ameloblastomas was evaluated. Seven acceptable cases were found and one additional example is added in this article. These rare tumors have occurred in cats over the age of 6 years, affected both sexes, both jaws, and various breeds. Two microscopic variants have so far been reported, namely the follicular pattern and the keratinizing pattern, which is similar to the keratinizing ameloblastoma in dogs. Ameloblastomas in cats have been confused in the past with two other feline odontogenic tumors: the inductive fibro-ameloblastoma (feline inductive odontogenic tumor) and the "calcifying epithelial odontogenic tumor" (amyloid-producing odontogenic tumor).     

Expression of laminin-5 in ameloblastomas and human fetal teeth

Extracellular matrix proteins have been shown to play important roles in the cell migration and differentiation in both normal and pathological conditions. In the present study, we used immunohistochemistry and in situ hybridization to determine the distribution of laminin-5 in ameloblastomas and developing human teeth. In ameloblastomas, the immunoreaction for the laminin-5 gamma2 chain was confined to the tumor cells of the peripheral area. The staining reaction was variable, being mostly weak and fragmented in the basement membrane structures surrounding the neoplastic islands. Some peripheral epithelial cells and some invading small ameloblastoma cell islands showed intense intracellular staining for the gamma2 chain. Tumor cells in the proliferating areas of ameloblastomas expressed gamma2 chain mRNA. The laminin-5 gamma2 chain was located beneath the dental lamina and in the outer, but not in the inner, enamel epithelium of the developing teeth. During the early hard tissue apposition stage, intense staining for the gamma2 chain was confined to ameloblasts, which also gave a strong signal for gamma2 chain mRNA. These results suggest that laminin-5 may contribute to the infiltrative and progressive growing potential of ameloblastomas. During human tooth development, however, laminin-5 may participate in the terminal differentiation of ameloblasts and in enamel matrix formation.     

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目的检测凋亡抑制蛋白Livin在人成釉细胞瘤（ameloblastomas,ABs）中的表达,探讨ABs发生发展中Livi。的作用及其与ABs临床生物学行为的关系。方法2007--2012年中国医科大学口腔病理科的存档蜡块选取80例ABs标本和10例口腔鳞状细胞癌（oscc）标本,以及同期口腔颌面外科门诊术中取材的30例ABs标本和智齿拔除术中的10例正常黏膜（NOM）,应用免疫组化法、Western—blot方法和RT—PCR法分别检测Livin蛋白和mRNA的表达情况,并进行统计学分析。结果（1）免疫组化：Livin在NOM中的表达呈阴性;在OSCC中Livin阳性表达;ABs中的阳性率为88．75％（71／80）,以中度阳性和强阳性表达为主,定位于牙源性上皮的外周柱状或立方状细胞及中心星网状层胞质中。（2）Western—blot：Livin在ABs中的表达高于NOM（P〈0．05）,而在ABs和OSCC组织中的表达差异无统计学意义（P〉0．05）。（3）RT—PCR：在ABs和OSCC中Livin的表达高于NOM,差异有统计学意义（尸〈0．05）。结论ABs中Livin在mRNA水平和蛋白质水平上表达都上调,并且Livin有胞浆的表达,提示Livin在ABs的发生和发展中发挥重要的功能。     

Altered expression of collagen XVII in ameloblastomas and basal cell carcinomas

BACKGROUND: Collagen XVII (BP180) is an epithelial transmembrane protein, which presumably plays a role in cell migration and differentiation under both physiological and pathological conditions. Ameloblastoma, the most common odontogenic neoplasm, and basal cell carcinoma (BCC) of the skin exhibit similar growth patterns and share histological features. METHODS: Here, we examined the distribution and expression of collagen XVII in ameloblastomas and BCCs using immunohistochemistry and non-radioactive in situ hybridization. In both tumors, the distribution of collagen XVII varied in different parts of the lesions. RESULTS: In ameloblastomas, immunostaining for collagen XVII was usually localized in the basal and suprabasal cells of the tumor nests, although in some tumors, a diffuse intracellular staining was detected in the central cells of the neoplastic islands. In BCCs, collagen XVII was mostly seen as diffuse cytoplasmic staining in some central and peripheral cells of the tumor islands and also at the cell membranes in the basal keratinocytes of the epidermis overlying the tumor nests. Double immunostaining with antibody against gamma2 chain of laminin-5 showed that these two components of the keratinocyte adhesion complex are usually co-localized in ameloblastomas and BCCs. In both tumors, collagen XVII mRNA was found in the basal epithelial cells and in some central and peripheral cells of the tumor islands, while the stromal cells were negative. CONCLUSIONS: These findings indicate that the expression of collagen XVII may be differentially regulated in various parts of the tumor. Diffuse intracellular distribution of collagen XVII and a consequent loss of critical cellular attachments may contribute to the infiltrative and progressive growing potential of tumors.     

Desmoplastic and non-desmoplastic ameloblastoma: a comparative clinicopathological analysis

OBJECTIVES: The aim of this study was to review a large series of ameloblastomas, accessioned during a period of 35 years in a single Oral Pathology Diagnostic Center, for the incidence of desmoplastic ameloblastoma (DA) and in order to analyze the clinical features of this unusual variant.
MATERIALS AND METHODS: All cases diagnosed as ameloblastoma were reviewed and 14 were rediagnosed as DA. These cases were analyzed in terms of gender, patient age, location, clinical diagnosis, radiographic features and recurrence following treatment. Data from DA and non-desmoplastic ameloblastoma (NDA) were compared.
RESULTS: The incidence of DA in this series was 8.8%. The mean age of NDA and DA were 39.1 and 38.8 years respectively, and a higher female prevalence was observed in the latter. The mandible was the most affected bone in both groups of tumors, but with a different regional distribution. Most NDA arose in the angle and ramus of the mandible, but the premolar/molar region was the preferential location for DA. The most common radiographic feature in DA was the osteolytic type, either monolocular or multilocular. Most of these cases were clinically diagnosed as ameloblastoma. According to follow-up data available, 21.4% of DA and 10.1% of NDA recurred.
CONCLUSIONS: The results of this study do not support the hypothesis that DA should be a separate clinicopathological entity. It seems most likely that DA is another his-tologic variant of ameloblastoma.     

Immunohistochemical biomarkers in ameloblastomas

Ameloblastoma is an aggressive odontogenic tumour, which is locally invasive and highly recurrent. Studies show that ameloblastoma is a benign odontogenic neoplasia, being relatively rare and occasionally presenting behaviour of malignant lesions. In addition to these particularities, the histological diagnosis of ameloblastoma can be challenging when the tumour shows high rates of mitosis, absence of nuclear pleomorphism, basilar hyperplasia and neural invasion. In order to help in the diagnosis, prognosis and treatment of this neoplasia, some immunohistochemical markers were shown to be associated with tumoural epithelium. The identification of these markers as well as of their association with clinical signs can be useful to elaborate more efficient treatment strategies and to control this pathology, including improvement of the quality of life of patients affected by this neoplasia. This article aims to review some markers associated with specific molecular pathways, bone remodelling, cell proliferation, apoptosis, cell signalling and tumour suppression.     

肿瘤相关巨噬细胞和MMP-2在成釉细胞瘤中的表达及意义

目的：探讨肿瘤相关巨噬细胞（ TAMs）和基质金属蛋白酶?2（ MMP?2）在人成釉细胞瘤（ ABs）中的表达及意义。方法：采用免疫组化通用二步法,分别检测43例ABs和10例正常口腔黏膜中CD68标记的巨噬细胞数目及MMP?2的表达情况。结果：TAMs和MMP?2在ABs中的表达均高于正常黏膜,差异有统计学意义（ P＜0．01）。在ABs中,TAMs主要表达于肿瘤间质,MMP?2主要表达于肿瘤实质,MMP?2表达强度随着TAMs计数增加而增加,二者呈正相关关系（ r＝0．331,P＜0．05）。结论：ABs中TAMs和MMP?2的共同表达可能在其发生发展中发挥重要作用。     

钙化上皮瘤及牙源性钙化上皮瘤的临床病理分析

目的：探讨钙化上皮瘤及牙源性钙化上皮瘤的临床表现、诊断及外科处理原则。方法：对13例钙化上皮瘤和4例牙源性钙化上皮瘤患者的临床资料进行回顾性分析。结果：所有患者均经手术治疗。钙化上皮瘤患者平均年龄11．2岁,小于10岁者占69．2％（10例）;位于头颈部8例（61．5％）,四肢4例（30．8％）,躯干1例（7．7％）。牙源性钙化上皮瘤患者平均年龄38．75岁,均位于颌骨。两种肿瘤无明显性别差异,均有复发、恶变的报道。结论：钙化上皮瘤和牙源性钙化上皮瘤在临床表现和病理诊断上具有明显差别,是两种不同的肿瘤;牙源性钙化上皮瘤具有局部浸润性生长,手术切除必须彻底。     

Lectin histochemistry of ameloblastomas and odontogenic keratocysts

The cell membrane carbohydrate components of 10 simple (follicular and/or plexiform pattern) and 5 acanthomatous ameloblastomas, one plexiform unicystic ameloblastoma, one soft tissue ameloblastoma and 11 odontogenic keratocysts were studied in paraffin-embedded tissues using horseradish peroxidase-conjugated lectins. The presence of glucose and mannose was demonstrated by intense labelling with Concanavalin ensiforme (Con A) in 73% of the ameloblastomas examined, while periodate oxidation of the specimens prior to Con A (PA/Con A) stained 53% of the cases. Ameloblastomas did not express receptors for Triticum vulgaris (WGA), Erythrina chrystagalli (ECA), Arachis hypogea (PNA), and Ulex europaeus (UEA-1). The plexiform unicystic ameloblastoma and the soft tissue ameloblastoma examined showed the same cell membrane glycoproteins as the simple and acanthomatous ameloblastomas. Forty-five per cent of the keratocysts demonstrated Con A reactivity from the basal to the keratinized layer, while 72% of these specimens showed positive PA/Con A reactivity from the parabasal to the keratinized layer. Staining with WGA, ECA, PNA, and UEA lectins also revealed the presence of N-Acetyl-glucosamine and fucose oligosaccharides in the plasma membrane of basal, spinous and keratinized cell layers of the odontogenic keratocysts. The distinct cell surface carbohydrate composition of the ameloblastoma and odontogenic keratocyst may be responsible for the differences in biological behavior in these conditions.     

牙源性腺样瘤的临床病理及其分子表达研究

牙源性腺样瘤(AOT)是一种良性肿瘤或错构瘤,对其性质及起源问题尚存在争论.本文就牙源性腺样瘤的临床病理、治疗、生物大分子在牙源性腺样瘤中的表达及起源方面的近期研究进展作一综述.     

Immunoexpression of BMP-2 and BMP-4 and their receptors,BMPR-IA and BMPR-II,in ameloblastomas and adenomatoid odontogenic tumors

ObjectivesThe present study evaluated the immunohistochemical expression of BMP-2 and BMP-4 and of their receptors (BMPR-IA and BMPR-II) in solid ameloblastoma (SA), unicystic ameloblastoma (UA) and adenomatoid odontogenic tumor (AOT) in order to obtain a better understanding of their role in the development and biological behavior of these tumors.DesignThis study analyzed these proteins in 30 cases of SA, 10 cases of UA, and 30 cases of AOT. Immunoexpression was evaluated in the parenchyma and stroma by attributing the following scores: 0, no stained cells; 1, ≤10%; 2, >10% and ≤25%; 3, >25% and ≤50%; 4, >50% and ≤75%.; 5, >75% stained cells.ResultsIn SAs, positive correlations were observed between the stromal and parenchymal expression of BMP-2 (p < 0.001) and between the stromal expression of BMP-2 and BMP-4 (p = 0.020), as well as between the stromal expression of BMPR-II and BMP-4 (p = 0.001) and the stromal and parenchymal expression of BMPR-II (p < 0.001). In UAs, correlations were detected between the stromal and parenchymal expression of BMP-4 (p = 0.035) and between the stromal expression of BMP-4 and BMPR-IA (p = 0.022). In AOTs, analysis of immunoexpression in the parenchyma revealed positive correlations between all proteins.ConclusionBMPs and their receptors play an important role in the differentiation and development of ameloblastomas and AOTs, but may not explain the different biological behaviors of these lesions. The positive correlation observed in AOTs might be related to the formation of mineralized material in this tumor.     

Blood group antigens A and B in ameloblastomas, odontogenic keratocysts and non-keratinizing cysts

abstract — The expression of blood group antigens A and B has been studied in 8 ameloblastomas, 16 odontogenic keratocysts from patients with basal cell nevus syndrome, 11 odontogenic keratocysts from patients without the syndrome, and 12 non-keratinizing odontogenic cysts, using a double layer immunofluorescence staining technique. The amount of antigen in the lesions was compared with the content of antigen in normal buccal mucosa from each patient. All ameloblastomas reacted negatively, three cysts from the patients with the basal cell nevus syndrome reacted negatively, and the odontogenic keratocysts from patients without the syndrome as well as the non-keratinizing odontogenic cysts all gave a positive reaction.     

Histopathologic study of epithelial components in the connective tissue wall of unilocular type of calcifying odontogenic cyst

Histopathologic study of satellite cysts and odontogenic epithelial islands in connective tissue wall of unilocular type of calcifying odontogenic cyst (COC) was made. The material was 13 cases consisting of 3 simple unicystic COCs, 9 odontome producing COCs and 1 ameloblastomatous proliferating COC. Satellite cysts were found in 6 cases, and were histologically classified into following types: simple cystic, odontome producing and ameloblastomatous. Histologic types of satellite cysts did not coincide with those of main cystic lesions in some cases. Odontogenic epithelial islands with or without proliferating feature were found in 9 cases, and were found in all cases with satellite cysts. Melanin and melanocytes were seen in an ameloblastomatous satellite cysts of 1 of 3 pigmented COCs.     

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提要：从1971年至今,世界卫生组织已就牙源性肿瘤及相关病变的分类进行了3次编撰和修订,这一过程反映了几十年来人们通过大量的研究对这一类病变认识的不断深入。本文选取几种常见的牙源性病变,包括成釉细胞瘤、牙源性腺样瘤、牙源性角化囊性瘤及牙源性钙化囊性瘤等,回顾其组织学分类及命名的变迁,以期从另一个角度深化对这些病变的认识。