Introduction

Odontogenic tumours literally meaning neoplasm arising from the tissues of the odontogenic apparatus. These tumours are derived from ectodermal tissue (epithelial tumours) or from mesodermal tissue (connective tissue tumours), or are composed of both components (mixed or composite odontogenic tumours). While these tumors are rarely malignant or metastatic (that is, they rarely spread to other parts of the body), and progress slowly, the resulting lesions can cause severe abnormalities of the face and jaw. Additionally, because abnormal cell growth easily infiltrates and destroys surrounding bony tissues, wide surgical excision is required to treat this disorder.

Case report

A middle-aged female about 36 years old sought treatment for a disfiguring mandibular swelling in the anterior region, present for 2 years. She revealed a history of insidious onset as a small, painless, non tender nodule about 2 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.

Fig-1	Fig-2

Extra-oral examination of the patient revealed symmetrical enlargement on 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 left posteriors 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

(A) Radiographs:

(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.
  
  

  Fig-3

  
  
  

  (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 4] 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.
  
  
  histopathological features
  
  The desmoplastic ameloblastoma is characterized by: [1],[3],[4],[5]

  • 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.
    
    

    Fig-4

    
    
    

    Thus histologically the desmoplastic ameloblastoma has to be differentiated from basal cell type ameloblastoma, ameloblastic/odontogenic fibroma or a squamous odontogenic tumor. [1],[4] 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. [3]
    
    Management
    
    Enucleation or curettage alone of the lesion may lead to recurrence, [4] as there is indistinct boundary between the tumor and normal tissue. Therefore complete resection and regular follow up is recommended. [1],[3] . The patient was investigated preoperatively and was prepared for general anaesthesia and resection of the segment of mandible was planned under general anaesthesia. The ameloblastic anterior mandible was exposed by giving two incisions leaving a spindle shaped island of skin on the specimen. The leasion was exposed by stripping the periostium both labially anb lingually. The mandible was resected bilaterally at the body. The specimen was taken out and the defect was reconstructed using reconstruction plate. The genioglosys and the geniohyoid muscles were tied to the  reconstruction plate and the incisions were closed.    
    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. [1],[5] 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. [5]
    
    

Fig-5	Fig-6
Fig-7	Fig-8
Fig-9	Fig-10

Discussion

Desmoplastic ameloblastoma can be considered as a rarity with unusual radiographic and histologic features.[3] Its incidence is very low as compared to that of the follicular or plexiform variants [1] 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. [1],[3] The most commonly reported site of occurrence is maxilla followed by mandible in the anterior-premolar region.[4] 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. [1] The present case however differed from this in that the patient was a male and the site of occurrence was mandible.

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.

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