The desmo- and osteoplastic ameloblastoma. Histologic variant or clinicopathologic entity? Case reports

Desmoplastic histological subtype of ameloblastoma in 16 dogs

Ameloblastoma in dogs most often has a highly conserved acanthomatous cell morphology and is recognized as canine acanthomatous ameloblastoma (CAA) while conventional ameloblastoma (CA) makes up a smaller yet morphologically diverse group of epithelial odontogenic tumors. In humans, a rare desmoplastic histological subtype has distinctive clinical, radiological, and microscopic features. Desmoplastic ameloblastoma (DA) has not previously been described in dogs, although it has been rarely referenced in the veterinary literature. This is the first thorough description of a case series of DA in dogs and describes clinical presentation, diagnostic imaging findings, histopathological features for diagnosis, and treatment outcome. Clinically, DA most often presents as a mass or swelling in the rostral mandible or maxilla of middle age to older dogs. On diagnostic imaging, the lesion has a radiolucent or mixed pattern with well-defined borders and variable loculation. As a solid, fibrous tumor with obscured odontogenic epithelium, DA is challenging to diagnose histologically and can mimic several other oral tumors, both benign and malignant. As an ameloblastoma, the biological behavior of DA is locally destructive yet benign and prognosis is favorable following surgical excision.

A Curious Case of Hybrid Ameloblastoma

Ameloblastoma is one of the most prevalent odontogenic tumors of epithelial origin, with several histological variations. However, among these variants, 'hybrid ameloblastoma' is infrequent and anomalous. The current case study demonstrates the existence of hybrid ameloblastoma in a 27-year-old female patient, which included desmoplastic, follicular, and acanthomatous patterns. The right side of the mandible was affected by tumor growth, with extensive bone involvement and neural invasion, resulting in a loss of sensation on that side. Although the tumor grows at a gradual pace, its enigmatic manifestation highlights the significance of a meticulous diagnosis. The course of treatment involved comprehensive resection of the tumor segment, followed by the recommended reconstructive surgery during the postoperative follow-up period.

Retrospective analysis of Desmoplastic Ameloblastoma: Clinical review

BACKGROUND

Desmoplastic Ameloblastoma (DA) is a rare, true neoplasm of jaws with reported incidence of 4-13% among other variants of Ameloblastoma, however this appears distinct than the classic Ameloblastoma in anatomical distribution and clinical presentation. This is often mistaken as a fibro-osseous lesion because of its similar radiological appearance.

MATERIAL AND METHODS

To describe the clinical, radiographic and histopathological characteristics through a series of new cases of histologically proven DA including a case of an exceptionally large, recurrent lesion along with retrospective analysis of cases from literature available for an improved understanding of the behaviour and prognosis of DA. A total of 50 cases were analysed for the anatomical distribution, radiographic presentation and management. Out of the 50 cases, 47 cases were from the English literature reported from 2011 to 2019 and 3 were new cases.

RESULTS

DA showed a slight male predilection (male: female=1.17:1) with a predominance in the fourth and fifth decade of life. Mandibular involvement (52%) was more commonly seen with a marked tendency for the anterior region. Radiographically, most of the lesions presented mixed radiopacity with radiolucency(80%) and root displacement was observed in only 70.27 % cases. Recurrence rate of 26 .47 % was observed. Cases treated with resection resulted in lesser recurrence as compared to those treated with enucleation and curettage.

CONCLUSIONS

DA is distinguished by a peculiar display of clinicalopathological parameters. DA has tendency of local disposition and propensity of recurrence, which thus necessitates its aggressive management. It is not possible to conclude or report on the aggressive/recurrent nature and appropriate treatment modality for DA due to inadequate follow-up results.

Hybrid Ameloblastoma of Anterior Maxilla: A Rare and Puzzling Pathologic entity - Case Report with Systematic Review

Hybrid ameloblastoma has a variable clinical, radiological, and histopathological presentation. They contain two or more different histologic types and their biologic comportment is still arguable. We herein present a case of a hybrid variant of desmoplastic ameloblastoma which is the first of its kind to have ever been reported due to its unusual location in the maxillary anterior region, along with systematic review of clinicopathologic features of reported cases immunohistochemical markers may act as an adjunct in the accurate diagnosis of these lesions.

A mixed radiopaque - radiolucent lesion in the anterior mandible associated with multiple impacted teeth: A radiodiagnostic challenge?

Desmoplastic ameloblastoma (DA) exhibits important differences in gender, anatomic distribution, radiographic findings, and histologic appearance compared to other types of ameloblastoma. Radiologically, DA is seen either as ill-defined mass containing osteolytic and sclerotic areas or as multifocal radiodense flecks within radiolucent background resembling a honeycomb. The radiographic differential diagnosis includes fibro-osseous lesions such as cemento-ossifying fibroma, fibrous dysplasia, calcifying odontogenic cyst, and chronic sclerosing osteomyelitis. Thus, DA should primarily be included in the differential diagnosis of a mixed radiopaque-radiolucent lesion with diffuse borders in the anterior premolar region of the jaws. This report adds to the literature of mixed radiolucent-radiopaque lesions which may not always be histopathologically diagnosed as a fibro-osseous lesion but could turn out to be a DA. This report also benefits the dental community by cautioning them to be aware of DA that can be associated with multiple unerupted teeth which is quite a rare finding.

Hybrid ameloblastoma: a mystified histopathological entity

Ameloblastoma a benign neoplasm of the maxillofacial region has been divided into various histopathological types by WHO. A more complex and confusing type includes hybrid type, which as the name suggest include more than two variants mostly histopathological. Various authors have reported cases of this type but the exact histopathological features are still unclear and each case that is being reported add to the literature, which further strengthens its histopathological feature. Also, this is a lesion whose clinical and radiographical features are similar to all the variants and a definitive diagnosis is achieved by histopathology only. Here, we present a case of hybrid ameloblastoma with striking and unique histopathological features.

Clinicopathological characteristics of desmoplastic ameloblastoma: A systematic review

The aim of the present review was to systematically present the clinicopathological data of desmoplastic ameloblastoma (DA) from articles published in the literature. A comprehensive search of the databases (PubMed, Medline, SCOPUS, Web of Science, and Google Scholar) for published articles on DA was conducted. A total of 238 cases were identified and analyzed from 76 published papers. DA showed a slight male predilection (male: female=1.07:1) with a predominance in the fourth and fifth decades of life. Mandibular involvement (52.55%) was most commonly seen with a marked tendency for the anterior region (mandible: 40.9%, maxilla: 48.07%). The size of the lesion ranged from .5 cm to 20.4 cm, with the majority of cases measuring more than 3 cm in size (53.84%). Radiologically, most of the lesions presented mixed radiolucency and radiopacity (62%), and root resorption was observed in only seven cases. The majority of the lesions showed ill-defined margins upon radiographic examination (65.78%). Most of the cases were treated with resection (78.57%), and five of the 10 recurrent cases were treated by enucleation/curettage. DA is characterized by the unique presentation of clinicopathological parameters. It is not possible to comment on its aggressive/recurrent nature and best treatment modality due to inadequate follow-up data.

Desmoplastic Ameloblastoma Arising in a Dentigerous Cyst - A Case Report and Discussion

Dentigerous cyst is a fairly common odontogenic cyst with an uncomplicated prognosis. However, reports of odontogenic and non-odontogenic tumors arising from the cysts have been published for many years. Therefore, the importance of thorough histopathological examination and regular follow-up cannot be overemphasized. Here is a case report of a possible development of desmoplastic ameloblastoma from a dentigerous cyst. This case is unique for two main reasons. Firstly, to our knowledge such a case has not been reported previously. Secondly, the tumor seemed to arise from the capsule and not from lining of the dentigerous cyst. Transformation of odontogenic rests into cysts is known to occur in the syndromic cases of odontogenic keratocysts (resulting in recurrent and daughter cysts) but not in dentigerous cysts. This case report may prompt greater interest in the role of the supposedly inactive odontogenic nests in the capsule of these cysts.

Cone beam computed tomography signs of desmoplastic ameloblastoma: review of 7 cases

OBJECTIVE

This study aimed to evaluate and summarize the radiographic features of desmoplastic ameloblastoma (DA) on cone beam computed tomography (CBCT) scans and to provide necessary further information for clinical diagnosis and preoperative assessment.

STUDY DESIGN

Seven cases with pathologic diagnosis of DA were studied retrospectively. A CBCT scan of each individual was analyzed and compared with its corresponding plain (panoramic) radiograph.

RESULTS

We found that 71.4% of lesions were located in the anterior or premolar regions (or both) and showed root displacement. With the advent of CBCT imaging, most DA lesions (57.1%) were perceived as having honeycomb appearance totally or dominantly. Distinctively, all the lesions presented cortical expansion with perforation in the buccal/labial side.

CONCLUSIONS

The typical intralesional structure with honeycomb appearance and the dominant buccal/labial cortical expansion with perforation could be proposed as the characteristic features of DA on CBCT images. CBCT can provide more information for preoperative radiologic assessment of DA compared with panoramic radiography.

A repeatedly recurrent desmoplastic ameloblastoma after removal and allobone graft: Radiographic features compared with histological changes

A 40-year-old man suffered from a repeatedly recurrent desmoplastic ameloblastoma in the right maxillary anterior and premolar regions. During the first visit, the patient was provisionally histopathologically diagnosed with a developmental cyst, and it was confirmed to be unicystic ameloblastoma and resected. Four years later, the lesion recurred, and was diagnosed as a desmoplastic type of ameloblastoma and removed again. Then, 5 years after the second surgery, the lesion recurred again, and was diagnosed as a type containing a follicular pattern, recurrent ameloblastoma. A panoramic radiograph showed a multilocular and mixed radiolucent/radiopaque expansile lesion at the first visit, a unilocular cystic lesion confined to the premolar area at the second visit, and a small soap bubble appearance in the molar area in the final visit. Cone-beam computed tomographic images of the final recurrence of the tumor revealed multiple small cyst-like structures in the right maxillary anterior and posterior regions.

Comparative morphometric study of AgNORs in variants of ameloblastoma

Aims:

To compare the area and number of AgNORs (silver stained nucleolar organizer regions) by morphometry between follicular and plexiform variants of ameloblastoma in order to analyze their cell proliferation rates.

Materials and Methods:

This retrospective study was carried out on 30 cases each of follicular and plexiform ameloblastoma. The sections were obtained and stained with silver staining technique to identify the nucleolar organizer regions. AgNORs were quantified using two parameters; manual tag for the number of AgNORs and area measurement using the image analyzer software, Image-Pro-Express.

Results:

Morphometric area measurements of AgNOR were significantly higher for Plexiform ameloblastoma (0.831μm²) than follicular ameloblastoma (0.528μm²). Enumeration of the number of AgNORs showed a significantly higher number of AgNOR for follicular ameloblastoma (1.71) than plexiform ameloblastoma (1.43). Among the groups studied, follicular ameloblastoma was more aggressive than plexiform ameloblastoma, as it showed smaller AgNOR area and higher AgNOR number.

Conclusion:

The combination of counting the number and measuring the area of AgNOR dots showed a significant overall difference between AgNOR profiles of follicular and plexiform variants of ameloblastoma.

Giant neglected desmoplastic ameloblastoma: reconstruction with free fibula flap

The desmoplastic ameloblastoma (DA) is a rare variant of the conventional ameloblastoma. It accounts for only 4% to 13% of all ameloblastomas. In this article, we describe the case of a young child affected by a giant neglected DA of the jaw. Preoperative biopsy demonstrated the extremely rare osteoplastic variant of DA. The patient was submitted to segmental mandibulectomy and immediate reconstruction with a free fibula osseous flap. The postoperative period was uneventful. The patient was very satisfied with the functional and aesthetic results of the procedure. In case of such rare variants of ameloblastoma, it is mandatory to preoperatively recognize them to allow the adequate treatment modality to be provided.

Osteoplastic ameloblastoma: a case report and literature review

Ameloblastoma with bone formation is rare. We report a case of a 55-year-old woman with ameloblastoma accompanied by prominent osteoplasia. Histopathological examination exhibited an abundant stromal component between tumor nests. Therefore, she was diagnosed as the desmoplastic variant, except for the numerous bone trabeculae. The distinction between new bone formation and invasion of the bone marrow poses a problem. A thin rim of fibrous bone that can be accentuated by Masson-trichrome staining suggests the former.

Unicystic ameloblastoma with diverse mural proliferation - a hybrid lesion

A 46-year-old man was referred to our hospital for treatment, complaining of swelling on the right mandibular molar region. Radiographic examination revealed a well defined multilocular radiolucent lesion with root resorption of right lower anteriors and molars. Following biopsy, a diagnosis of unicystic ameloblastoma of mural type was made and hemimandibulectomy was performed under general anesthesia. Histopathological examination of the surgical specimen exhibited a unicystic ameloblastoma of luminal, intraluminal, and mural type. Intraluminal proliferation was of plexiform pattern and mural proliferation showed unusual histopathological findings, which revealed follicular, acanthomatous areas coexisted with desmoplastic areas. This mural picture was similar to the so-called 'hybrid lesion of ameloblastoma', whose biological profile is not elicited due to the lack of adequate published reports. Two years follow up till date has not revealed any signs of recurrence.

Desmoplastic ameloblastoma: a case report

Desmoplastic ameloblastoma is a rare variant of ameloblastoma. Up until now, less than 150 patients have been reported in the literature. We report a case of desmoplastic ameloblastoma in a 45-year-old female with a painless swelling in the left anterior maxillary region. Fine needle aspiration yielded no fluid. Periapical and panoramic radiographs as well as computer tomography scan showed a mixed lesion with multilocular appearance. The present case deserves special importance be-cause of its unfamiliar appearance, potentially aggressive nature and high chances of misdiagnosis. Moreover, the radio-graphic features of this lesion rarely point towards ameloblastoma. A partial maxillectomy for tumor resection was per-formed and the involved teeth were removed. This report is an attempt to help the dental community in developing familiarity with the clinical presentation and at the same time advocating to develop a high index of suspicion in recognizing such cases.

Desmoplastic ameloblastoma - A review

Among the ameloblastomas, the desmoplastic variation is rare. The desmoplastic ameloblastoma (DA) is characterized by specific clinical, imaging, and histological features. The here presented retrospective analysis investigated the clinicoradiographic features of an overall of 115 DA-cases, having been reported in literature from 1984 to 2008. DA showed a nearly equal male to female ratio (55/59) with a prevalence within the forth and fifth decades. Sixty-two lesions occurred in the mandible and fifty-one lesions in the maxilla. Clinically, a painless swelling with buccal extension was the most common presentation being found in 48 cases. Radiologically, the lesion often presented multilocular (49.3%; 36/73), mixed radiolucent/radiopaque (55.6%; 50/90) and with ill-defined borders (64.0%; 48/75). Whereas enucleation provided a recurrence rate of 21.1%, resection reduced this rate remarkably to 3.1%. The average period until recurrence was 36.9 months. Histologically, scattered epithelial nests and extensively desmoplasia were prominent features of DA. In conclusion, these retrospective results confirm the statement that DA is a variation among ameloblastomas. DA present clinicoradiographic and histologic distinct features, when compared with "conventional ameloblastomas".

Ameloblastoma and adenomatoid odontogenic tumor: the role of α2β1, α3β1, and α5β1 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.

Desmoplastic ameloblastoma featuring basal cell ameloblastoma: A case report

The desmoplastic ameloblastoma is a histological variant of ameloblastoma. The neoplastic epithelial islands seen in desmoplastic ameloblastoma are small and ameloblastic cells are rare. Basal cell ameloblastoma is also a rare variant of ameloblastoma, in which the tumor is composed of more primitive cells and has even fewer features of peripheral palisading. This report describes the case of a 17-year-old female with an ameloblastoma in the right anterior maxilla. Orthopantomography and computed tomography showed a well-defined lesion in the right maxilla. A partial maxillectomy for tumor resection was performed under general anesthesia. Histologically, ameloblastic tumor cells were seen with dense collagenous stroma and the tumor cells showed primarily basal cell variants of ameloblastoma. After 7 years of follow-up, clinical and radiographic examinations have revealed no evidences of recurrence.

Desmoplastic Ameloblastoma in the Mandible

The desmoplastic variant of ameloblastoma (DA) is characterized by unique histological and radiographic features. It is histologically characterized by an abundance of densely collagenous stroma with small nests and strands of likely compressed odontogenic epithelium. Although radiographic examination of ameloblastomas usually reveals unilocular or multilocular radiolucency, DA may appear as a mixed radiopaque-radiolucent lesion. In this case report, a 68-year-old man who had a complaint of a mass in his right mental region is presented. The patient was unable to wear his prosthesis because of an underlying swelling. An incisional biopsy was performed. Microscopic examination of the surgical specimen revealed large epithelial islands of ameloblast-like cells within increased, dense, collagenous desmoplastic stroma. Histopathologically, it was diagnosed as DA. Under local anesthesia, the lesion was enucleated. There was no recurrence after 32 months of follow-up.

Follicular/desmoplastic hybrid ameloblastoma with radiographic features of concomitant fibro-osseous and solitary cystic lesions

We report a case of ameloblastoma radiographically suggestive of a complication of fibro-osseous and solitary cystic lesions. A 35-year-old woman was referred to our hospital for treatment, complaining of swelling in the left premolar region of the mandible. Radiological findings indicated a mixed radiopaque and radiolucent lesion in the region of the left mandibular canine and first premolar as well as a solitary cystic lesion in the mandibular second premolar region. Following biopsy, resection of mandible was performed under general anesthesia. Histopathologic examination identified follicular-type ameloblastoma with partial desmoplastic findings. Conventional radiography and computed tomography were not useful in indicating the relationship between the mixed and solitary cystic lesions. However, magnetic resonance imaging was instrumental in elucidating this relationship.

Distribution of basement membrane type IV collagen alpha chains in ameloblastoma: an immunofluorescence study

BACKGROUND

Type IV collagen, a heterotrimeric molecule that exists in six genetically distinct forms, alpha1(IV)-alpha6(IV) is a major structural component of basement membrane (BM) and acts as a scaffold for other BM constituents.

METHODS

Indirect immunofluorescence using alpha chain-specific monoclonal antibodies was employed to clarify basement membrane (BM) collagen IV distribution in two ameloblastoma, and for comparison, on oral mucosa and tooth germ.

RESULTS

Ameloblastoma BM expressed five of six genetically distinct forms of collagen IV: alpha1(IV), alpha2(IV), alpha5(IV) and alpha6(IV) chains occurred as intense linear stainings without disruption around neoplastic epithelium, and this expression pattern was fundamentally similar to oral mucosa BM; alpha4(IV) expression was rare and occurred around nests of primitive tumor cells or potentially invasive sites. The tooth germ demonstrated a stage- and position-specific collagen IV distribution: the inner enamel epithelium BM expressed alpha1(IV), alpha2(IV), and alpha4(IV) except in the cuspal predentine region; and the outer enamel epithelium BM expressed alpha1(IV), alpha2(IV), alpha5(IV), and alpha6(IV) chains.

CONCLUSIONS

Results suggest that collagen IV alpha chain distribution in ameloblastoma BM plays an important role in tumor cytodifferentiation and progression.

Desmoplastic ameloblastoma (including “hybrid” lesion of ameloblastoma). Biological profile based on 100 cases from the literature and own files

The profile of the desmoplastic ameloblastoma (DA) is presented, based on a survey of 100 cases. DA is a benign, locally invasive variant of the intraosseous, infiltrative ameloblastoma (IA). Radiologically, the DA shows ill-defined borders with a soap bubble appearance. The finding of a mixed radiolucency-radiopacity in 52% of the cases often leads to a preoperative diagnosis of a fibro-osseous lesion. Association with an unerupted tooth is not a typical finding. The DA accounts for 4-13% of all ameloblastomas. The over-all average age is 42.9 years, higher for males (45.9 years) than for females (39.7 years). Thus, the DA occurs at a slightly higher age than the intraosseous ameloblastoma (37.4 years). The male/female ratio is 1:1. The maxilla/mandible ratio is 1/0.9 as opposed to 1/5.4 for the IA. Seven maxillary tumours involved an entire quadrant and 15 maxillary and mandibular tumours crossed the midline of the jaws. Pathogenetically, it seems that the DA is derived from the same sources as the IA, and extra-osseous sources do not seem to play a role. Histologically, the DA reveals the following morphological characteristics: the odontogenic epithelium occurs as irregular, stellate or follicular islands and cords, the center often appearing hypercellular with spindle-shaped or squamatoid cells. Peripheral columnar or cuboidal cells rarely reveal an ameloblast-like appearance. Thus, there are only vague tendencies to mimic a follicular ameloblastoma with acanthomatous features. The most striking feature separating the DA from IA is to be found in the tumour stroma: in DA there is extensive stromal desmoplasia with an abundance of thick collagen fibres that seem to compress the epithelial islands. Nine cases of so-called "hybrid lesion of ameloblastoma" where areas of IA coexist with areas of DA are surveyed in addition to the 100 cases of DA. No conclusions can be drawn about the biological profile of this variant due to the insufficient number of cases.

Hemangiomatous ameloblastoma: Clinical, radiologic, and pathologic features

A hemangiomatous ameloblastoma was present in the third molar region of the left mandible of a 26-year-old woman. The histology and radiologic features of this tumor differed from those of a conventional ameloblastoma. Its histologic features were consistent with those of a hemangiomatous ameloblastoma, and its standard radiologic features and computed tomography mimicked that of fibro-osseous lesions, whereas magnetic resonance imaging suggested a vascular lesion. The behavior and prognosis of the hemangiomatous ameloblastoma are uncertain because of the small number of documented cases and lack of long-term follow-up, but are thought to be similar to those of the conventional type. The relevant clinical, radiologic, and pathologic features of this case are presented.

Tratamento cirúrgico do ameloblastoma com reconstrução de mandíbula com enxerto de crista ilíaca não vascularizado: estudo de sete casos

OBJETIVO: Determinar a validade do enxerto autólogo de crista ilíaca não vascularizado no tratamento cirúrgico do ameloblastoma de mandíbula. MÉTODO: Nos Serviços de Cirurgia de Cabeça e Pescoço e Semiologia Bucal do Complexo Hospitalar Heliópolis, de 1980 a 2000, foram tratados 31 pacientes com ameloblastoma de mandíbula, dos quais sete receberam enxerto de crista ilíaca autólogo, fixos com placa de titânio do sistema A-0 (quatro casos) e aço inox (três casos), sendo portadores da variedade folicular (seis casos) e plexiforme (um caso). RESULTADOS: Nesta análise, foi utilizado o Teste de Hipótese para a média populacional com a variança desconhecida, houve exposição da placa em três casos (40%) quando a neoplasia ultrapassava a linha média e em quatro casos (60%) não incidiu nenhuma complicação. CONCLUSÕES: Apesar da incidência de exposição de placa, o método é indicado na reconstrução da mandíbula de pacientes com ameloblastoma.

Desmoplastic ameloblastoma: a case report with fine-needle aspiration cytologic findings

A case of desmoplastic ameloblastoma of the maxilla in a 25-yr-old woman is presented. Smears prepared from fine-needle aspiration cytology showed two populations of cellular elements: cohesive epithelial clusters with basaloid morphology present, mostly in bidimensional, irregularly outlined clusters with ill-formed palisading of nuclei at the periphery in some, and a mesenchymal component represented by 1) a sparse chunk of moderate-sized tissue fragments made up of spindle- or ovoid-shaped nuclei entrapped in mesenchymal matrix, and 2) many dissociated naked oval-to-spindle-shaped nuclei. The presence of epithelial and mesenchymal components and their benign nature lead us to consider the possibility of benign odontogenic tumors 1) of epithelial origin, such as ameloblastma with a stromal component, e.g., desmoplastic ameloblastoma; 2) of mesenchymal origin, such as odontogenic fibroma; and 3) of mixed epithelial and mesenchymal origin, such as ameloblastic fibroma. Excision and histopathological examination of this lesion confirmed the diagnosis of desmoplastic ameloblastoma. In the given clinical setting and radiological examination, the above cytological features suggest a benign odontogenic tumor, rather than precisely diagnosing any of the entities mentioned above. However, it is important to distinguish between these, since the treatment varies accordingly. The differential diagnosis is discussed.

Clinical and histopathological analyses of desmoplastic ameloblastoma

Desmoplastic ameloblastoma (DA) is an unusual subtype of ameloblastoma characterized by pronounced desmoplastic stroma. There is, however, still argument whether DA is a distinct clinicopathologic entity. To enhance knowledge of DA, 7 cases of DA (7.9%) were retrieved from 89 ameloblastomas field in the Department of Oral Pathology, Hiroshima University School of Dentistry and analyzed clinicopathologically and histopathologically. The mean age of the patients with DA and non-DA at the time of the diagnosis was 40.6 +/- 5.9 years and 33.1 +/- 2.0 years, respectively. The male-to-female ratio was 2.5:1 in DA and 1.8:1 in non-DA. Four (57%) DAs were located in the maxilla where only 6% of the non-DA occurred. Interestingly, all DAs arose in the anterior/premolar area of the jaws and 6 cases were located mainly within the alveolus. None of the DA showed typical radiographic features of ameloblastoma. In 5 DAs, scattered radiopacities were observed in the radiolucent lesion and gave preoperative diagnoses of non-ameloblastomatous lesions or even osteosarcoma. All DAs showed pronounced desmoplastic stroma where there were compressed tumor islands usually lacking a peripheral layer of ameloblastic cells and a central zone of stellate reticulum. There was cystic change within the epithelial nests in 3 DAs and true glandular structures with mucus cells in a case of DA. Tumor islands often infiltrated into marrow spaces of surrounding bone. There was no capsule formation. Recurrence rate was 14% in DA and 20% in non-DA. The present study based on data of DA in the Japanese population supports that DA must be considered as a distinct clinicopathologic entity.

So-called 'hybrid' lesion of desmoplastic and conventional ameloblastoma: report of a case and review of the literature

So-called 'hybrid' lesion of ameloblastoma, which is composed of desmoplastic ameloblastoma and conventional follicular/plexiform ameloblastoma, is an unusual variant of ameloblastoma and only eight cases of 'hybrid' lesion have been published in the English literature. To enhance knowledge of this interesting tumor, we add a case of 'hybrid' lesion that occurred in the right mandible of a 48-year-old Japanese male. Radiographic examination disclosed a honeycomb appearance at the anterior alveolar region, combined with a unicystic radiolucency in the molar region of the mandibular body. Histologically, the former showed microscopic features of desmoplastic ameloblastoma and the latter those of follicular ameloblastoma with focal granular cell transformation. The lesion was enucleated with curettage of surrounding bone and the lesional cavity was marsupialized. Although tumor tissues reappeared at 3, 5, 7 and 14 months after the surgery, the patient has remained disease free for 11 years after the last vaporization by CO2 laser of the recurred tumor. Many more cases of 'hybrid' lesion are needed to clarify the clinicopathological, histopathological and biological characteristics of this interesting variant of ameloblastoma.

Unicystic ameloblastoma. A review of 193 cases from the literature

Based on a world-wide literature survey of 193 published cases of unicystic ameloblastomas (UA), data have been produced allowing the presentation of a revised concept of this much debated lesion. UA is a variant of the solid or multicystic ameloblastoma. Radiographically, the unilocular pattern is more common that the multilocular, especially in cases associated with tooth impaction. However, it is stressed that although the lesion is pathomorphologically unicystic, it will far from always produce a unilocular radiolucency. The mean age at the time of diagnosis of UA is closely related to an association with an impacted tooth. Almost 20 years separate the mean age of the 'dentigerous' variant from the 'non-dentigerous' (16.5 years versus 35.2 years) The male:female ratio for the 'dentigerous' type is 1.5:1, but for the 'non-dentigerous' type it is reversed (1:1.8). Location favours greatly the mandible (mandible to maxilla = 3 to 13:1). Between 50 and 80% of cases are associated with tooth impaction, the mandibular third molar being most often involved. The 'dentigerous' type occurs on average 8 years earlier than the 'non-dentigerious' variant. The mean age for unilocular, impaction-associated UAs is 22 years, whereas the mean age for the multilocular lesion unrelated to an impacted tooth is 33 years. Histologically, the minimum criterion for diagnosing a lesion as UA is the demonstration of a single cystic sac lined by odontogenic (ameloblastomatous) epithelium often seen only in focal areas. This simple type of UA (according to the authors' modification of the classification by Ackermann et al. (Journal of Oral Pathology 1988; 17:541-546)), is one of four UA subtypes, the others being (1) simple with intralumenal proliferations; (2) simple with both intralumenal and intramural proliferations; and (3) simple with intramural proliferations only. All four subtypes occur in both the 'dentigerous' and 'non-dentigerous' variants. The simple subtype with and without intralumenal proliferations may be treated conservatively (enucleation), whereas subtypes showing intramural growths must be treated radically, i.e. as a solid or multicystic ameloblastoma. Finally, the authors disclose areas and issues pertaining to UA that still need to be addressed.

Desmoplastic variant of ameloblastoma in Chinese patients

Desmoplastic ameloblastoma is a rare tumour, and we know of only 43 previously reported cases. We report seven Chinese patients (five men and two women) with the desmoplastic variant of ameloblastoma, which makes up 9% of all ameloblastomas diagnosed during the years 1981-1995. The age ranged from 18 to 68 years (mean 43). Five of the tumours were in the maxilla and two were in the mandible. Five of them were situated anteriorly, the remaining two cases involving both anterior and posterior maxilla. The features of the 42 cases previously reported were reviewed and were compared with those in the present study. Our results differ in that we found a male predominance, wider age range and more tumours in the maxilla. Histologically, this variant of ameloblastoma is characterized by abundant collagenous stroma. Because the epithelial clusters may show prominent squamous metaplasia or may be compressed into thin strands in most areas, the appearance may mimic a squamous odontogenic tumour or odontogenic fibroma. The behaviour of this variant of ameloblastoma is likely to be the same as that of the classic ameloblastoma.

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 histologic variant of ameloblastoma.

Desmoplastic ameloblastoma: correlative histopathology, radiology and CT-MR imaging

A desmoplastic variant of ameloblastoma with osteoplasia in the stroma is reported. This tumour presented in the canine/premolar region of the left maxilla of a 31-year-old woman. It was treated by partial hemimaxillectomy and immediate reconstruction with a non-vascularised iliac graft. The location of this lesion, its histology and radiological features differ from those of the conventional ameloblastoma. The behaviour and prognosis of the desmoplastic ameloblastoma (DA) cannot at this stage be predicted due to the small number of cases that have been reported and a lack of long-term follow-up. To our knowledge this is the first documentation of the CT and MRI features of desmoplastic ameloblastoma with pathologic correlation.

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.

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.