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Clinicopathological Study and Treatment Outcome of 40 Cases of Ameloblastoma  -  A Seven Year Retrospective Report

Authors: Vibha Singh*, Satish Dhasmana**, Shadab Mohammad***, Candradhar Dwivedi****
*Associate Professor, **Assistant Professor, ***Professor & Head, ****Senior Resident

Institution: Department of Oral and Maxillofacial Surgery & Department of Anesthesia, C.S.M. Medical University Lucknow, India

Corresponding Author:  

Dr Vibha Singh
Associate Professor
Department of Oral and Maxillofacial surgery
C.S.M.Medical University
A-43 Krishna Nagar Lucknow. India
 
E Mail   drvibha66@yahoo.com

Abstract:

Forty cases of ameloblastoma are reported.  Over two-thirds had a tumor size of over 10 centimeters.  Because of the large size of the tumor and perforation of the cortical bone with spread into the soft tissues, 22 patients (55%) were treated with mandibular resection with reconstructive plating but without bone grafting.  This aids in the detection and treatment of possible recurrences.  Three patients broke their reconstructive plate during the postoperative period.  All three patients underwent successful revision with reconstructive plating and bone grafting.  The patients were followed between two to five years.  No recurrences were noted in the 35 patients who underwent mandibular resection.   However, four out of five patients that were treated with curettage developed a recurrence. 

 
Introduction:

Ameloblastoma is a rare benign tumor accounting for 1% of mandibular and maxillary tumors and cysts.1  In its early stages it is confined to the bone but large tumors can break through the cortex and involve the soft tissues. The tumors are known for their propensity for local recurrence, especially if soft tissue invasion or cortical bone perforation has occurred.

Histologically, the tumors may have a follicular, plexiform, acanthomatous or cystic pattern.2  On x-ray the tumors have either a multilocullar (80%) or unilocular (20%) pattern.3  A follicular ameloblastoma had the highest recurrence rate.2  A unicystic pattern had the second highest recurrence rate.2

Inadequately treated and longstanding tumors can rarely undergo malignant transformation which is defined as tumors having metastasized or “cytological features of malignancy” in the primary tumor.4  The term “malignant ameloblastoma” is preferred for those tumors that have a benign appearance but have metastasized and the term “ameloblastic carcinoma” for tumors with a malignant histological appearance regardless of mestastasis.5  As of 2007, only 35 cases of ameloblastic carcinoma have been reported in the English literature.5  Recurrence of disease may be delayed with reports of recurrences 21 and 28 years after resection.6,7

Methods:

Forty cases of ameloblastoma were treated at  the OPD of the Department of Oral and Maxillofacial surgery, CSMMU from 2003-2010.   77.55% of the patients were male and 22.5%, were female.  The majority of the patients were between the ages of 18 and 40 with only one patient below the age of 18 (see Table 1).  The mean age was 38.3 years.   The majority of patients had advanced disease with over two-thirds of the patients having a tumor size of 10 cm or greater. 

The patients were treated with a variety of modalities depending upon the extent of the tumor and the presence of soft tissue and cortical invasion.   Surgical approaches included:  Segmental resection without continuity defect (12.5%), mandibular resection with bone grafting with reconstruction plate (20%),  mandibular resection with reconstruction plate without grafting (55%), and curettage (12.5%).  Patients who underwent mandibular reconnection without grafting had soft tissue infiltration of the tumor.   The length of patient follow-up varied between two to five years. 

Treatment results, histopathological findings and recurrence rates are calculated and reported for the studied patients. 

Table 1:  Patient and Tumor (Ameloblastoma) Size

Patient and Tumor Characteristics Category Total
   Age  < 18 yrs 1 (2.5%)
  18-40 29 (75.5%)
  >40 11 (27.5%)
   Ethnic  Indian all
   Gender male 31 (77.5%)
  female 9 (22.5%)
    Site mandible 38 (95%)
  maxilla 2 (5%)
    Clinical tumor size <5 cm 3 (7.5%)
  5-10 cm 10 (25%)
  >10 cm 27 (67.5%)
    Pathological fracture Yes 1 (2.5%)

Table 2:  Tumor (Ameloblastoma) Location

  Site of Ameloblastoma Number Percentage
     Maxilla 2 5%
        Posterior region  1  
        Anterior region  1  
    Mandible  38 95%
        Posterior 32  
        Anterior 6  
        Crossing midline  2  
    Total  40 100%

Table 3:  Ameloblastoma - Radiology and Histopathology Findings

  Radiologic and Histopathologic Findings  Category Total
    Radiographic pattern Unilocular 8 (20%)
  Multilocular 32 (80%)
    Cortical bone  Torn 32 (80%)
  Expanded 7 (17.5%)
  Preserved 1 (2.5%)
    Basal cortical bone  Torn 32 (82%)
  Expanded 7 (17.5%)
  Preseved 1 (2.5%)
    Histological pattern  Follicular 15 (37.5%)
  Cystic 8 (20%)
  Follicular & Plexiform 7 (17.5%)
  Plexiform 6 (15%)
  Acanthomatous 4 (10%)

Table 4:  Treatment Results

  Treatment  Total Number Recurrence
    Segmental resection  5 (12.5%) none (0%)
     Resection, reconstruction with bone graft & bone plate 8 (20%) none (0%)
     Resection, reconstruction with bone plate 22 (55%) none (0%)
    Curettage  5 (12.5%) 4 (80%)
  Location of Recurrence     
     Mandible 38 3 (7.9%)
     Maxilla 2 1 (50%)

 
Results

The results and analysis showed that the incidence of ameloblastoma has a male-to-female ratio of approximately 3 to 1.  The mean age was 38.3 years.  The most common age group was between 18-40 years of age, least common was below 18 years of age. 

Ameloblastomas, predominantly are found in the mandible (95%) and in the maxilla (5%).  The most common site was the posterior mandible in 32 patients (the anterior mandible was involved in 6 patients).  In two patients the lesion crossed the midline.  

Only two patients had maxillary lesions, one in a posterior location and one anterior.   The pictures below are from a young girl with a maxillary ameloblastoma. 

Appearance of a 12 year old young girl with a left maxillary ameloblastoma  Amelioblastoma of Maxillay Bone - Preop Photo    Pre-operative Orthopantomogram showing an ameloblastoma in the left maxillary bone.  Orthopantomagram of Ameloblastoma of the Maxilla 
         
Patient appearance three months after surgery  Post op photograph after resection of ameloblastoma    Post-operative orthopantomogram three months after resection of a left maxillary ameloblastoma  Post op orthopantomogram after resection of a ameloblastoma 
 

The size of the tumors was greater than 10 cm in 67.5% of patients.  Only three patients had a tumor size less than 5 cm.  Below is a picture of a patient with a large ameloblastoma. 

Appearance of a 45 year old male with a right mandibular ameloblastoma  Preoperative Appearance of a Fory Year Old Male with a Large Mandibular Amelioblastoma    Preoperative orthopantomogram showing a large ameloblastoma destroying the right mandible.  Orthopantomogram of a Large Mandibular Amelioblastoma 
         
During surgery the mandible was resected and a reconstructive plate placed.  A bone graft was not inserted because of soft tissue invasion.     Surgical resection and plating of the mandible after removal of a large ameloblastoma    Picture of the surgical specimen  Ameloblastoma - Surgical Specimen 
         
Patient appearance three months after surgery  Post op photograph of patient after removal of a large mandibular ameloblastoma       

Soft tissue infiltration was present in 87.5% of the cases.  The radiographic appearance was multilocular in 80%of the cases whereas 20% of the cases were unilocular.  Cortical plates were torn in 80%, and in 82% basal bone was also expanded.  In only one patient was there no expansion of the cortical plate. 

Histopathological reports indicated that the most common variant was follicular ameloblastoma (37.5%) and cystic ameloblastoma  (25%).

Three patients reported with fractured reconstruction plates.  Recurrence was most common with a rate of 80% in patients who underwent curettage (10% of total patients) and in patients having a maxillary location (2.5% of total patients).  Partial maxillectomy and mandibulectomy were performed in the recurrent cases.


Discussion:

Similar to the findings of Fregnari, et.al.3 80% of our tumors were located in the posterior mandible and the majority of patients were in the fourth decade between the ages of 18 to 40.  Average age of presentation that has been reported in the literature is between 30 and 33 years.2,3  In our patients, the mean age of presentation was 38.3 years.  

The majority of our patients presented with very large tumors, with 67.5% of patients having a tumor size of greater than 10 cm (see Table 1).  Radiology studies found cortical bone torn in 80% of the patients and pathological studies demonstrated soft tissue infiltration in 87% of patients. Follicular histopathology was found in 37.5% of our patients.

Large size, cortical rupture, soft tissue invasion and follicular histology are all predictors of recurrence.3  The total recurrence rate for most studies has been between 13.3% and 22%.2,3  Because of this, a large number of patients (55%) were treated with resection and plating without reconstruction.  This will allow easier detection and management of future recurrences. Three patients treated with this technique developed a complication with the fracturing of the reconstruction plate during the follow up period.  All three patients underwent successful revision with bone graft and reconstructive plating.  

Curettage was used in the minority of the patients with small tumors and was associated with the highest (80%) recurrence rate.  These findings are similar to Lau8 who reported a 30.5% recurrence rate with enucleation as compared to 3.5% with segmental resection.  Reduced recurrences were noted in patients undergoing enucleations who were also treated with the application of Carnoy’s solution (a fixative composed of ethanol, chloroform and acetic acid).  

Despite the large tumors in our patient population, recurrences were not observed in patients undergoing mandibular resection.  As opposed to curettage, resection allows for a greater margin of clinically uninvolved tissue around the tumor.  All of our patients require long term follow-up since recurrences have rarely been reported 20 to 30 years after resection.6,7  This finding has been observed by other authors and has lead to Chana9 and Disa10 recommending the treatment of resection with a free fibular flap reconstruction.  Chana also reported good results with and recommends simultaneous placement of osseointegrated implants during the primary procedure.9 

Conclusion 

The authors have evaluated, clinical, radiographic and histopathological findings of 40 cases of ameoblastoma from a single Institute treated by one team during 2003-2010.  The results show that tumors were predominantly solid and affected the  posterior mandible.  The data showed that the cases treated by segmental resection developed no recurrences, but cases treated by curettage had a significant number of recurrences.  The presence of ruptured basal cortical bone, and histological pattern seems to be an important factor for the management of ameloblastoma. 

 
References:

1.  Vayvada H, Mola F, Menderes A, Yilmaz M. Surgical management of ameloblastoma in the mandible: Segmental mandibulectomy and immediate reconstruction with free fibula or deep circumflex iliac artery flap (evaluation of the long-term esthetic and functional results). J Oral Maxillofac Surg. 2006 Oct;64(10):1532-9.   View Abstract

2.  Krishnapillai R, Angadi PV. A clinical, radiographic, and histologic review of 73 cases of ameloblastoma in an Indian population. Quintessence Int. 2010 May;41(5):e90-100.  View Abstract

3.  Fregnani ER, da Cruz Perez DE, de Almeida OP, Kowalski LP, Soares FA, de Abreu Alves F. Clinicopathological study and treatment outcomes of 121 cases of ameloblastomas. Int J Oral Maxillofac Surg. 2010 Feb;39(2):145-9. Epub 2009 Dec 31.  View Abstract

4.  El-Sissy NA   Immunohistochemical detection of p53 protein in ameloblastoma types Eastern Mediterranean Health Journal Volume 5, Issue 3, 1999, 5(3) 478-489   View Abstract 

5.  Lolachi CM, Madan SK, Jacobs JR. Ameloblastic carcinoma of the maxilla. J Laryngol Otol. 1995 Oct;109(10):1019-22. View Abstract

6.  Adebayo ET, Fomete B, Adekeye EO. Delayed soft tissue recurrence after treatment of ameloblastoma in a black African: Case report and review of the literature. J Craniomaxillofac Surg. 2010 Jun 26. PMID:  View Abstract 

7.  Vasan NT. Recurrent ameloblastoma in an autogenous bone graft after 28 years: a case report. N Z Dent J. 1995 Mar;91(403):12-3.   View Abstract

8.  Lau SL, Samman N. Recurrence related to treatment modalities of unicystic ameloblastoma: a systematic review. Int J Oral Maxillofac Surg. 2006 Aug;35(8):681-90. Epub 2006 Jun 16.  View Abstract

9.  Chana JS, Chang YM, Wei FC, Shen YF, Chan CP, Lin HN, Tsai CY, Jeng SF. Segmental mandibulectomy and immediate free fibula osteoseptocutaneous flap reconstruction with endosteal implants: an ideal treatment method for mandibular ameloblastoma. Plast Reconstr Surg. 2004 Jan;113(1):80-7.   View Abstract 

10.  Disa JJ, Cordeiro PG. Mandible reconstruction with microvascular surgery. Semin Surg Oncol. 2000 Oct-Nov;19(3):226-34.   View Abstract 

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World Articles in Ear, Nose and Throat  www.waent.org                 Sept. 3, 2010              Vol 3-2

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