Year : 2006 | Volume
: 17 | Issue : 1 | Page : 45--49
Desmoplastic ameloblastoma : Report of a unique case and review of literature
Hiral Desai1, Ramita Sood2, Raksha Shah1, Jyoti Cawda1, Haren Pandya2,
1 Department of Oral Pathology and Bacteriology, Government Dental College & Hospital, Ahmedabad, India
2 Department of Oral & Maxillofacial Surgery, Government Dental College & Hospital, Ahmedabad, India
Department of Oral & Maxillofacial Surgery, Government Dental College & Hospital, Ahmedabad
Desmoplastic Ameloblastoma is a rare variant of ameloblastoma. 90 cases of desmoplastic ameloblastoma have been reported so far in literature. We are presenting a rare case of desmoplastic ameloblastoma in the ramus region of mandible with regards to its clinical and radiographical viewpoints. Only one other case of desmoplastic ameloblastoma has been reported in the ramus region of mandible of the 90 cases that we have reviewed. Review of literature has revealed the tumour to most commonly occur in the 3rd to 5th decade of life with a high preponderance of Japanese males. The anterior region of either jaw was most commonly found to be affected. Radiological appearance was most commonly of a mixed radio-lucent/radio-opaque type with a high incidence of poorly defined borders. However our case differed from the reviewed cases as it was found to be a unilocular lesion with well defined borders. Histopathological findings of our case were consistent with the hisotpathological appearance of the reviewed cases and showed extensive stromal desmoplasia and small tumour nests of odontogenic epithelium scattered in stroma.
|How to cite this article:|
Desai H, Sood R, Shah R, Cawda J, Pandya H. Desmoplastic ameloblastoma : Report of a unique case and review of literature.Indian J Dent Res 2006;17:45-49
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Desai H, Sood R, Shah R, Cawda J, Pandya H. Desmoplastic ameloblastoma : Report of a unique case and review of literature. Indian J Dent Res [serial online] 2006 [cited 2022 Jul 5 ];17:45-49
Available from: https://www.ijdr.in/text.asp?2006/17/1/45/29892
Ameloblastomas are benign locally aggressive, polymorphic neoplasms of proliferating odontogenic epithelial origin. The incidence, clinical, radiological features, behavior and histopathology of ameloblastomas have been extensively reviewed in numerous publications. Several histopathologic patterns of ameloblastomas are commonly described and include the follicular, plexiform, acanthomatous, granular cell and basal cell patterns. There appears to be rather general agreement that these variations in histopathoogy patterns do not have any significant bearing on prognosis except unicystic ameloblastoma because of less aggressive behavior and favorable prognosis.
Eversole et al , 1984 I was the first to describe 3 cases of desmoplastic variant of ameloblastoma. Later, Waldron and El Molly  reported an additional 14 cases and since then 73 cases have been reported in literature taking the total no of reported cases to 90. This unusual variant was characterized histologically by extensive stromal collagenisation or desmoplasia with small nests and strands of odontogenic epithelium. hnmunohistochernical studies suggest that the desmoplasia originate from de novo synthesis of extracellular matrix proteins .
However desmoplastic ameloblastomas do not present typical clinical or radiographic features that are of other variants of ameloblastoma. Clinically this tumor has a predilection for occurrence in anteriorposterior region of maxilla or mandible. This variant presents radiologically as unilocular or multilocular radiolucencies or in most cases their radiographic appearances are often more typical of the fibro-osseous lesions with well- defined or poorly defined borders. Though very little information appears in literature either due to insufficient number of cases reported or due to variations in the clinical or radiological criteria, the pathologist may sometimes fail to diagnose the tumour or differentiate it from either ameloblastoma or other odontogenic tumours.
The purpose of this article is to present a case of desmoplastic ameloblastoma that has occurred in an unusual site and has a unique radiographic appearance and to provide a brief review of literature.
A 32 year old male was referred to the government dental college and hospital, Ahmedabad in June 2001 with the chief complaint of swelling and pus discharge in relation to right lower mandibular 2 nd and 3rd molar region. The patient stated that the swelling had been present since 1 1/2 months and gave history of severe throbbing, continuous pain and swelling on the right side at the angle of mandible below the ear region. General dentist gave the treatment of pain relief in form of drugs. There was no history of trauma or any remarkable medical history. Clinical examination revealed firm, tender, swelling in the right mandibular region with normal mucous membrane covering. No lymphadenopathy on palpation was noted. Intra-oral examination revealed a painful, non mobile, bony hard, diffuse swelling on the buccal aspect distal to right second molar extending into vestibule upto the coronoid process in the rams region of the mandible. Periodontal pocket with pus discharge was observed in relation to the distal aspect of right 2°a molar. There was no intra oral sinus or ulceration. There was no recurrence.
A panoramic radiograph showed a well defined unilocular radiolucency around 3 tins, in size extending from right lower impacted third molar to coronoid notch involving whole of ramus. The coronoid and condylar processes were found to be normal but slight break in continuity of anterior border of ramus was present [Figure 1]. From these clinical and radiographic findings a possible diagnosis of a dentigerous cyst, arneloblastoma or odontogenic keratocyst was made. To obtain a correct diagnosis an excisional biopsy was taken and the lesion was diagnosed as desmoplastic ameloblastoma. Specimen showed marked stromal desmoplasta characterized by moderately cellular fibrous connective tissue with abundant collagen formation and presence of small ovoid or follicle shaped islands of odontogenic epithelium. The epithelial cells about the periphery of the epithelial islands were columnar in appearance and some of the follicles showed cystic degeneration [Figure 2].
All laboratory investigations were carried out and found to be within normal limits before the surgical procedure. The patient refused to give his consent for resection as is the accepted treatment modality in such cases; hence it was decided to completely enucleate the lesion.
Extraction of right 2nd molar and impacted 3rd molar was carried out simultaneously. No evidence of tumour extending into the surrounding soft tissue could be clinically detected. Post surgical histopathological examination showed the stromato be heavily collagenized and composed of fibrous connective tissue with extensive desmoplasia Tumour nests of odontogenic epithelium showed follicles which are composed of peripheral palisading layers of columnar cells and stellate cells in the central area.
In some follicles nuclear polarity was seen in peripheral areas. [Figure 3,4]. Few mature bony trabaculae were seen at the periphery of the tumour [Figure 5]. Typical desmoplastic lesions can usually be identified as such due to consistent stromal desmoplasia characterized by moderate cellular fibrous connective tissue with abundant collagen formation. Narrow zones of loose myxoid stroma adjacent to epithelial islands are also found. Duct like spaces may be present within epithelial islands and there may be presence of central cysts as seen in our case [Figure 2].The patient was kept on a strict follow up every 3 months to detect any early signs of recurrence. No recurrence has been seen since the last 2 years.
REVIEW OF LITERATURE
Desmoplastic ameloblastomas have been widely reported in the last two decades since its first description given by Eversole et al  in 1984. Total number of 90 cases have been reported in literature until now; the addition of our case takes the number to 91 cases. Some of the data was collected using the medline data base although the information available for each case was not uniform partially due to the multitude of languages which could be misinterpreted during processing; hence some variation in clinical, radiological and histopathological criteria maybe seen.
Despite these limitations, all cases were evaluated in according to the above mentioned criteria's. The patient's age, gender, race, tumour site, location and radiographic appearance were tabulated [Tablel 3]. According to our review of 90 cases, the incidence of this variant of ameloblastorna ranges from 0.9%-12.1% of all types of ameloblastornas. Despite the unknown racial origins of 38 cases, desmoplastic ameloblastoma was most commonly found in Japanese (n=19) and Chinese (n=15) patients and predominantly seen in the 3rd to 5th decade of life. However this lesion was commonly seen in males (45.55%) rather than in females (37.77%) a feature almost similar to classic ameloblastoma [Table 1].
Among the sites of 89 of 90 previously reported cases, marked predilection of occurrence of desmoplastic ameloblastorna was found in the mandible (57.3%) rather than in rnaxilla(42.7%), [Table 2]. In our review, tumour location was specifically mentioned in 58 of 90 cases amongst which 9 cases (17.65%) were found in anterior region of mandible and 11 cases (28.95%) were found in anterior region of maxilla showing almost an equal distribution. Tumour was found most extensively involving the anterior, premolar and molar regions of maxilla (23.68%) as compared to mandible where only 3 cases (5.88%) were reported. [Table 2] Only 1 other case besides our case was found in the molar-ramus area .
On examination of the radiographic borders of 72 reported cases of this tumour 41 cases (56.94%) were seen in mandible and 31 cases (43.05%) were seen in maxilla. Of these, poorly defined borders were reported in 33 cases (80.49%) and 27 cases (87.1 %) in the mandible and in the maxilla respectively. Well defined borders were seen in only 12 cases of which 8 cases (19.51%) were in mandible while only 4 cases (12.9%) were reported in maxilla In terms of radiographic appearance, out of 71 cases reported, 45 cases (63.38%) were found in the mandible and 26 cases (36.61%) were found in the maxilla In maxilla, an equal number (50%) of this tumor was found to be of a mixed as well as of the radiolucent variety. In mandible, majority of reported cases were of mixed type (60%). [Table 3].
Histopathologically, the less aggressive odontogenic fibroma or squamous odontogenic tumour may mimic this tumour. In majority of reviewed cases the histopathological findings described by Eversole et al  were consistent. These tumours were composed of desmoplastic connective tissue stroma in which epithelial islands of varying sizes and shapes were present. These islands were peripherally surrounded by columnar cells and centrally by stellate reticulum like cells. The majority of cases showed flattened or cuboidal cells at the periphery of islands but in some cases nuclear polarization of peripheral cells and micro cyst formation in the centre were also noted.
The desmoplastic ameloblastoma is an unusual variant of ameloblastoma, which has a low occurrence rate and is characterized by marked stromal desmoplasia. In accordance with our reviewed cases, these tumours were most commonly found in 3rd to 5th decade of life with a high predominance among males. The Japanese race was found to be most affected . These lesions however showed striking variation in anatomic and radiographic appearance. Most of the tumours showed slightly higher rate of occurrence in mandible as compared to maxilla [Table 2]. The study of 17 cases by Kezler et al  also showed mandible to be involved in 83% and maxilla to be involved in 17% cases. According to our review, predilection of occurrence were seen in anterior region of either maxilla or mandible as also reported by Kawai et al . However our case differed considerably because of its occurrence in the molar ramus region of mandible.
Radiographically, desmoplastic ameloblastoma may show either a multilocular, mixed radiolucent/ radioopaque appearance or multifocal appearance of minute flecks of bone similar to that seen in benign fibro osseous lesions. As per the reviewed cases majority of desmoplastic ameloblastomas showed mixed radiolucent/radioopaque appearance which can be due to infiltrative growth pattern of tumour cells into surrounding marrow spaces and simultaneous vigorous osteoblastic activity leading to number of bony flecks which gives a mixed radiolucent/radioopaque appearance . The high incidence of poorly defined borders reported in previous cases can be attributed to the pattern of infiltration into marrow spaces and lack of demarcation of fibrous connective tissue. These features may also be of prognostic significance in predicting tumour behaviour.
Histopathology showed extensive stromal desmoplasia and small tumor nests of odontogenic epithelium [Figure 3,4]. The epithelial cells about the periphery of the epithelial islands are usually cuboidal and occasionally hyperchromatic , however occasional islands showing columnar peripheral cells with reversed nuclear polarity are also found as seen in our case [Figure 3]. Although, this tumor is somewhat histologically different from other odontogenic tumors like ameloblastic fibroma, odontogenic fibroma or squamous odontogenic tumor. In our case diagnosis was not difficult because the stroma showed extensive desmopastic proliferation without cellular connective tissue and some of the tumour nests showed clear follicular patterns with ameloblastic polarization [Figure 3]. The simultaneous presence of osteoplasia and desmoplasia as seen in connective tissue stroma of this tumour has been reported in only four other cases ,. Philipsen et al  suggested that the stromal osteoplasia is not a part of reparative process but may be due to metaplastic changes in the stroma caused by tumor cell stimulation of mesenchymal cells. These metaplastic trabeculae consisted of woven bone, contained large osteocytes and were surrounded by active osteublasts that were randomly scattered in to stroma. He hypothesized that mixed radiolucent/radio opaque appearance of some lesions may be attributed to these metaplastic foci. In our case, very few mature bone trabaculae were observed in connective tissue stroma [Figure 5]. These findings suggested that bone tissues in the tumor were the remnants of resorbed bone caused by tumor expansion and production of new bony trabeculae around this resorbed bone was seen to repair the damage caused by tumor expansion.
Thus, we conclude on the available information that desmoppaasic ameloblastoma showing a radiographic appearance resembling fibro osseous lesions many times needs a perfect diagnosis based not only on the clinical and radio graphical appearance but also on the histopathological findings. The lesion in the present case deviates from the usual desmoppaasic variant of ameloblastoma in terms of site and radiological appearance. So it is essential on the surgeon's part to establish the definitive diagnosis to prevent any error in formulating treatment modalities.
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