|Year : 2008 | Volume
| Issue : 4 | Page : 146-150
Desmoplastic ameloblastoma of anterior mandible: Case report of a rarity
Department of Oral Medicine and Radiology, Pacific Dental College and Hospital, Debari, Udaipur-313 024, Rajasthan, India
|Date of Web Publication||18-Jun-2009|
"Himadri", 62, Sarvritu Vilas, Udaipur-313 001, Rajasthan
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Ameloblastoma, one of the most common odontogenic tumors of the jaws, presents classical clinical, radiographic and histopathological diagnostic features exhibiting a benign but locally aggressive and destructive clinical course with a high rate of recurrence. A case of desmoplastic ameloblastoma of mandible is discussed in this article, which presents itself as a rare variant of ameloblastoma with unusual inconclusive clinico-radiographic features to be diagnosed as classical ameloblastoma and difficult to differentiate from other suspected multilocular benign odontogenic or reactive lesions of the jaws. It is the typical histopathological picture of the lesion exhibiting a blend of desmoplasia (collagenization) and ameloblastoma that leads to its final diagnosis and determines its management.
Keywords: Ameloblastoma, collagenization, desmoplasia, desmoplastic ameloblastoma
|How to cite this article:|
Nahar P. Desmoplastic ameloblastoma of anterior mandible: Case report of a rarity. J Indian Acad Oral Med Radiol 2008;20:146-50
|How to cite this URL:|
Nahar P. Desmoplastic ameloblastoma of anterior mandible: Case report of a rarity. J Indian Acad Oral Med Radiol [serial online] 2008 [cited 2020 Jul 7];20:146-50. Available from: http://www.jiaomr.in/text.asp?2008/20/4/146/52830
| Introduction|| |
Ameloblastoma, one of the most common odontogenic tumors of epithelial origin in the jaws clinically presents as non tender bony or cystic swelling, reaching enormous size with passage of time, exhibiting a moderate to slow rate of growth causing marked facial disfigurement, asymmetry and displacement of vital adjacent structures.  The most common site and age of occurrence is mandibular molar-ramus region in 3 rd and 4 th decade of life. In behavior they are histologically benign (except the ameloblastic carcinoma) but locally aggressive and destructive with a high rate of recurrence. , Although they may be diagnosed clinically from their appearance and radiographic features, the final diagnosis depends on the histopathologic findings, which usually classify ameloblastoma as following types: ,
- Acanthomatous (or Squamous metaplastic)
- Granular Cell
- Basaloid (or Basal Cell)
- Telangiectatic (or Hemangiomatous)
- Ameloblastic Carcinoma / Malignant Ameloblastoma.
However, it was only in 1984 that Eversole et al . discovered a new and unusual histologic variant known as desmoplastic ameloblastoma.  This discovery was substantiated by reports of similar cases by El Mofty and Waldron in 1987 and a very few others thereafter.  In 1992, WHO recognized it as a variant of ameloblastoma.  The term 'desmoplastic' or 'desmoplasia' stands for histologic finding of abundant stroma with pronounced collagenization. Thus desmoplastic ameloblastoma is a variant of benign ameloblastoma histologically characterized by extensive stromal desmoplastic proliferation. ,
| Case Report|| |
A middle-aged male about 31 years old sought treatment for a disfiguring mandibular swelling in the anterior region, present for 15 years. He revealed a history of insidious onset as a small, painless, non tender nodule about 15 years ago gradually reaching the present extent without any pain, tenderness, paresthesia except drifting and mobility of mandibular anterior teeth and difficulty while eating food, speaking and tongue movements due to size of the mass. There was no relevant history of any trauma or infection in the region before the inception of the swelling. The patient did not seek any result-oriented treatment except extraction of right mandibular lateral incisor about 2 years ago, which had been drifted and tilted. There was non-significant past medical and family history. The patient was found to be of an average build, had normal gait with no physical handicap and was alert, conscious, cooperative and responsive to verbal commands with vital parameters within normal range.
Extra-oral examination of the patient revealed asymmetrical enlargement on right mandibular anterior region [Figure 1] which on palpation was found to be non tender, ill defined, firm to hard in consistency, fixed, non reducible and non pulsatile roughly extending from right premolar to left premolar region. The upper 2/3 rd of the face, bilateral TMJs, regional nodes and neck revealed no pathology.
Intra-oral examination revealed fair oral hygiene, a complete set of permanent dentition with missing right mandibular lateral incisor and anterior crossbite. A growth [Figure 2] was revealed in the mandibular anterior premolar region with distinct labio-buccal and lingual portions grossly measuring about 8 × 8 cm in size. The labio-buccal portion extended from 46 to 36 causing elevation of the floor of the vestibule and cortical expansion. On palpation it was non tender, firm in consistency overall but fluctuant in 41 to 34 region, irregular in shape with ill defined margins, non reducible, non pulsatile and fixed. There was a depression in 42 region dividing the swelling into two unequal halves. The lingual portion presented as a dome shaped singular mass extending from 45 to 35 with obliteration and elevation of the floor of mouth causing postero-superior displacement of tongue in rest position. It had other characteristics similar to the labio-buccal counterpart. The overlying mucosa appeared stretched and pale pink with no signs of sinus or discharge. The overall swelling had led to mobility of 41 to 34 and drifting of 44 to 31. Maxilla, palate and other components of oral cavity were normal with no apparent pathology. Based on history and clinical findings, the provisional diagnosis of an odontogenic tumor was made.
| Investigations|| |
(1) OPG [Figure 3]: revealed
- an ill defined multilocular radiolucency with irregularly thickened cortical lining extending from 43 to 36, causing expansion of the lower border of the mandible in the symphysis region;
- another ill defined mixed radiopaque - radiolucent mass extending from 46 to 33 exhibiting irregularly thickened trabeculae with specks of calcification;
- resorption of roots 32 to 35, mesioangular tipping of 41.
(2) True occlusal view mandible [Figure 4]: revealed
- an ill defined mixed radiopaque-radiolucent mass extending from 46 to 35 on lingual aspect and from 46 to 33 on buccal aspect, revealing irregularly thickened trabeculae with specks of calcification and bicortical expansion;
- tipping and drifting of 41 horizontally towards 31.
(B) Hemogram and Serum Chemistry values were within normal range.
(C) FNAC of the swelling yielded clear yellow fluid which on histopathological examination supported the diagnosis of an odontogenic tumor.
The overall clinical and radiographic features were suggestive of a mixed solid and cystic odontogenic tumor, probably an ameloblastoma, with differential diagnosis of CEOT, odontogenic myxoma, central giant cell granuloma, or ameloblastic fibroma.
(D) Incisional Biopsy: the histopathologic evaluation of the specimen [Figure 5] revealed an abundant collagenous fibrous connective tissue stroma interspersed with islands and cords showing peripherally compressed ameloblast-like cells surrounding a central area of spindle or polygonal shaped stellate reticulum cells. Some of the islands demonstrated cystic changes. The overall histopathological features were suggestive of ameloblastoma with desmoplasia showing cystic changes.
| Final Diagnosis and Treatment Performed|| |
The overall clinical, radiological and histopathological picture was suggestive of desmoplastic ameloblastoma with mixed solid and cystic changes. Based on this diagnosis, the patient underwent resection of mandibular segment extending from 46 to 36 and extraction of 47 in the Department of Oral and Maxillofacial Surgery. The missing segment was surgically reconstructed [Figure 6] and the resected segment [Figure 7] was sent for histopathological evaluation, which confirmed the biopsy findings. After the surgery the patient had an acceptable, esthetic facial profile [Figure 8] and was put on periodic recall for further necessary treatment and rehabilitation.
| Discussion|| |
Desmoplastic ameloblastoma can be considered as a rarity with unusual radiographic and histologic features. Its incidence is very low as compared to that of the follicular or plexiform variants  and till date only a few cases have been reported in literature. Clinically it usually presents as a tumor or swelling with a growth potential and local aggressiveness at par with other variants. No reports of malignant form have yet been reported. , The most commonly reported site of occurrence is maxilla followed by mandible in the anterior-premolar region. This is in striking contrast to that of the usual clinical site of ameloblastoma. The mean age of occurrence is between the 3 rd and 5 th decade with slight female and no racial predilection and duration ranging from as short as 2 months to as long as 16-18 years.  The present case however differed from this in that the patient was a male and the site of occurrence was mandible.
Differential diagnosis of radiographic features
The other benign variants of ameloblastoma usually present as: ,
- well defined or circumscribed unilocular/ multilocular radiolucency,
- mostly associated with unerupted tooth and
- causing cortical expansion (with erosion sometimes) and displacement of adjacent vital structures.
The desmoplastic variant exhibits atypical and varied radiographic features as: ,,
- localized irregular multilocular radiolucency with indistinct borders, or
- a mottled, radiopaque/ radiolucent appearance with ill defined margins, or
- a massive expansile osteolytic lesion with honeycomb, mottled or multilocular appearance
(a), (b), (c) with unclear boundary between the tumor and normal tissue.
These varied radiographic appearances at various jaw sites make desmoplastic ameloblastoma radiographically resemble ameloblastoma, CEOT, odontogenic myxoma, central giant cell granuloma or ameloblastic fibroma in mandible; and AOT, Fibro-osseous lesions, radicular or globulomaxillary cysts in maxilla. 
Differential diagnosis of histopathological features
A classic ameloblastoma (e.g. follicular variety) is characterized by: 
- islands, nests and cords of odontogenic epithelium rimmed by columnar cells resembling ameloblasts;
- center of these epithelial structures contains loosely arranged spindle or stellate shaped cells resembling stellate reticulum of a developing tooth;
- surrounding fibrous connective tissue stroma of mature collagen.
The desmoplastic ameloblastoma is characterized by: ,,,
- abundant desmoplastic (or collagenous) proliferation of the stroma;
- loss of cell rich connective tissue;
- tumor elements present at the periphery of the lesion, absence of capsule;
- existence of some ameloblastoma like structures with peripherally compressed ameloblasts;
- some cystic or myxoid changes can also be seen.
Thus histologically the desmoplastic ameloblastoma has to be differentiated from basal cell type ameloblastoma, ameloblastic/odontogenic fibroma or a squamous odontogenic tumor. , Hence a pathologist may fail to recognize and diagnose desmoplastic variant accurately if the specimen contains only a small amount of biopsied material.
Such a sort of stromal desmoplasia is not restricted to jaw bones alone, rather it is encountered in a variety of other benign and malignant epithelial neoplasms e.g. morphea variant of basal cell carcinoma, desmoplastic follicular carcinoma of thyroid, scirrhous carcinoma of the breast, benign papillary proliferation of the breast. 
Significance of Desmoplasia: The mere presence of extensive desmoplasia in epithelial tumors is of unknown significance. However, it has been speculated that such an extensive stromal desmoplasia in these tumors might inhibit the growth of tumor cells.  This has been indirectly supported by Shivas and Douglas who reported a longer survival rates in patients with elastosis in breast carcinoma. 
| Management|| |
Enucleation or curettage alone of the lesion may lead to recurrence,  as there is indistinct boundary between the tumor and normal tissue. Therefore complete resection and regular follow up is recommended. , Recurrence rate and prognosis of this variant is unknown because of the small number of cases reported in the literature and lack of long-term follow-up. , However, on the basis of the histological features, it has been suggested by El Mofty and Waldron that it may have a propensity to recur at least as often as other ameloblastic variants. 
| Conclusion|| |
It can be seen from the foregoing discussion that histopathological studies are mandatory for the correct diagnosis of desmoplastic ameloblastoma as clinical and radiographic features alone are inconclusive. Still some more endeavor and zest is needed for an insight into the etiopathogenesis, clinical course and prognosis of this rare and interesting variant of ameloblastoma.
| Acknowledgment|| |
I am thankful to the Departments of Oral Medicine and Radiology, Oral and Maxillofacial Surgery and the Department of Oral Pathology, Nair Hospital Dental College, Mumbai for their cooperation.
| References|| |
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|4.||El Mofty SK, Waldron CA. A histopathologic study of 116 amelobalstomas with specialreference to the desmoplastic variant. Oral Surg 1987;63:441. |
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]