Ameloblastoma Revisited

A network meta-analysis assessing the effectiveness of various radical and conservative surgical approaches regarding recurrence in treating solid/multicystic ameloblastomas

Multiple treatment approaches have been undertaken to reduce the incidence of recurrence in solid/multicystic ameloblastoma (SMA), both conservative and radical. A network meta-analysis (NMA) was conducted to assess and compare the effectiveness of these various treatment approaches concurrently. This study was reported based on the Preferred Reporting Items for Systematic Reviews for Network Meta-Analysis (PRISMA-NMA) statement. PubMed (MEDLINE), ScienceDirect, Scopus, and Web of Science were searched until August 10, 2021. The NMA was conducted using the STATA program. Of 1153 records identified in the search, seven observational studies with 180 patients were included. Six different treatment approaches were identified. Segmental resection ranked highest for reducing the recurrence rate with the highest SUCRA score (77.7), followed by curettage with cryotherapy (66.9) and marginal resection (49.3). Network inconsistencies and publication bias appeared to be absent. According to the Confidence in Network Meta-Analysis (CINeMa) method, the evidence's certainty was low for all comparisons due to imprecision and within-study bias. In conclusion, this study is the first NMA in the field of ameloblastoma. Segmental resection seemed to be the most effective treatment approach for minimizing recurrence in SMA patients. Nevertheless, weak certainty of evidence makes that the results must be regarded with caution.

Potential involvement of polycystins in the pathogenesis of ameloblastomas: Analysis based on bioinformatics and immunohistochemistry

OBJECTIVE

To perform an integrated analysis in identifying novel hub genes that could facilitate the diagnosis and targeted therapy of ameloblastoma.

DESIGN

The expression profiling dataset, GSE38494, was obtained from the Gene Expression Omnibus database. Differentially expressed genes were identified through GEO2R online tool and characterised via Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. The protein-protein interaction network and hub genes were screened using the STRING database and Cytoscape software. Subsequently, an upregulated gene was selected for further validation using the GSE132472 dataset. Further, immunohistochemistry was performed to assess the expression of the selected gene in ameloblastomas, odontogenic keratocysts, dentigerous cysts, and gingival tissues. The diagnostic and therapeutic utility of the selected hub genes were further verified by receiver operating characteristic analysis and the DGIdb database.

RESULTS

We identified six hub genes in ameloblastoma, among which the upregulated gene PKD2 and its related gene PKD1 were further validated. GO functional annotation revealed that PKD2 is involved in cell-cell junction, extracellular exosome, cytoplasm, endoplasmic reticulum, and calcium ion transport. The immunohistochemical analysis showed that the expression of polycystin-1 and polycystin-2, encoded by the PKD1 and PKD2 genes, respectively, was upregulated in ameloblastoma. PKD1 and PKD2 had a high diagnostic utility for ameloblastoma, and allopurinol interacted with the PKD2 gene.

CONCLUSION

Our research indicates that polycystins are highly expressed in ameloblastoma and might be involved in the oncogenesis of ameloblastoma, thus offering a new perspective on the molecular mechanisms and targeted therapies on ameloblastoma.

Roles of Proliferation and Angiogenesis in Locally Aggressive Biologic Behavior of Ameloblastoma versus Ameloblastic Fibroma

(1) Background: The present study was carried out to evaluate the roles of proliferation and angiogenesis in locally aggressive biologic behavior of ameloblastoma versus ameloblastic fibroma; (2) Methods: 30 formalin-fixed paraffin embedded blocks (15 cases of ameloblastoma and 15 cases of ameloblastic fibroma) were used. To evaluate the proliferation, the tissue sections were stained with an AgNORs stain. CD105 was used as an immunohistochemical marker of angiogenesis. Quantitative evaluations of AgNORs were performed. The mean vascular density was evaluated as a measure for CD105 protein expression by using image analyzer computer system; (3) Results: The mean number of AgNORs dots per nucleus was significantly higher in ameloblastoma as compared to ameloblastic fibroma. Additionally, the protein level of CD105 showed positive expression and wide distribution that the mean vascular density was significantly higher in ameloblastoma as compared to ameloblastic fibroma; (4) Conclusion: Quantitative evaluation of the AgNORs stain and the mean vascular density utilizing CD105 protein expression may reflect a higher proliferative activity and a more locally aggressive biologic behavior of ameloblastoma when compared to ameloblastic fibroma, indicating that other factors may be involved in biologic behavior of ameloblastic fibroma.

Conceptual changes in ameloblastoma: Suggested re-classification of a "veteran" tumor

OBJECTIVES

The merging of ameloblastoma (AM) with mural unicystic ameloblastoma (UAM-M) was suggested by the 2017 WHO based on similar treatment needs. In an international multicenter study, we investigated the characteristics of their merged product (merged-AM) and raised the possibility of unifying AM and UAM (total-AM).

MATERIALS AND METHODS

AM and UAM (luminal/intraluminal/mural), separate and combined, were analyzed for demographic/clinical/radiological features. ANOVA and chi-square tests were followed by univariate and multivariate analyses, and significance was set at p < .05.

RESULTS

The patients' mean age was 39.6 ± 20.3 years in merged-AM (147 AM, 76 UAM-M), 45.1 ± 19.4 years in AM (p = .009). Merged-AM comprised 51.3% multilocular/48.7% unilocular tumors, AM comprised 72.5%/27.5%, respectively (p < .001). Merged-AM was associated with impacted teeth in 30.8%, AM in 18% (p = .023). The probability of merged-AM for multilocularity increased by 2.4% per year of age (95%CI 0.6-4.2, p = .009). Association with impacted teeth decreased by 7.9% per year of age (95%CI 1.9-14.39, p = .009). Merged-AM did not differ from total-AM (p > .05).

CONCLUSIONS

Merged-AM partially differed from AM, but differences appeared to diminish in an age/time-wise manner. Merged-AM and total-AM were nearly indistinguishable. Therefore, AM and UAM may be considered a continuous spectrum of one type of tumor, further necessitating revision of the treatment approaches.

Global incidence and profile of ameloblastoma: A systematic review and meta-analysis

OBJECTIVES

To evaluate the global incidence of ameloblastoma and to provide a profile of ameloblastoma patients.

MATERIAL AND METHODS

A systematic review and meta-analysis was conducted. Searches were performed in PubMed, EMBASE, SCOPUS, and Web of Science for articles published from 1969 to 2018 for the global incidence and from 1995 to 2018 for the profile of ameloblastoma patients.

RESULTS

Seven studies on the incidence rate of ameloblastoma were included in the meta-analysis. These studies only covered Europe, Africa, and Australia. The pooled incidence rate was 0.92 per million person-years (95% CI: 0.57-1.49), with significant heterogeneity between studies. Forty-two articles provided profile data of 6,446 ameloblastoma patients. Mean age was 34 years and the peak age incidence in the third decade of life. In Europe and North America, ameloblastoma mostly occurred at an older age when compared to Africa and South America. A slight male preference (53%) was found, and the mandible appeared to be the preferred site. The most common type of ameloblastoma was multicystic. The histopathologic patterns were mostly follicular and plexiform.

CONCLUSIONS

This is the first study assessing the global incidence of ameloblastoma. The pooled incidence rate was determined to be 0.92 per million person-years.

Radical vs conservative treatment of intraosseous ameloblastoma: Systematic review and meta-analysis

OBJECTIVES

The aim of the present study was to assess the outcomes of radical and conservative treatment approaches of solid/multicystic and unicystic ameloblastoma in terms of recurrence rates.

MATERIAL AND METHODS

A systematic review and meta-analysis was conducted based on the PRISMA statement. Search was performed using PubMed, Embase, SCOPUS, and Web of Science for articles published from January 1969 until March 2018. Quality assessment of the selected articles was conducted using the Quality Appraisal of Case Series Studies Checklist. The meta-analysis was performed using the MedCalc program.

RESULTS

The search strategy yielded 6,984 articles; 20 studies met the eligibility criteria and were included in the meta-analysis. The pooled recurrence rate of solid/multicystic ameloblastomas following radical treatment was 8%, while conservative treatment caused recurrences in 41%. For unicystic ameloblastomas, these values were 3% and 21%, respectively. The risk of recurrences in both types of ameloblastomas following radical treatment was lower than following conservative treatment.

CONCLUSIONS

The present study showed statistically significant differences in recurrence favoring radical treatment for both unicystic and solid/multicystic ameloblastoma. The solid/multicystic type showed more recurrences than the unicystic type. Unfortunately, since only retrospective studies were available, the evidence is less strong as wished for.

Is conservative surgery a better choice for the solid/multicystic ameloblastoma than radical surgery regarding recurrence? A systematic review

PURPOSE

Determine if conservative surgery of primary solid/multicystic ameloblastoma (SMA) is capable of decreasing the recurrence rate as effectively as radical surgery.

METHODS

We searched in MEDLINE, Web of Science, Scopus and Cochrane Library for original studies reporting on the conservative or radical treatment of primary SMA and the related recurrence rate. All selected data were independently assessed. Meta-analysis was performed and the Relative Risk (RR) of recurrence with a confidence interval of 95% was the effect measure. P value for the summary effect of < 0.05 was considered statistically significant.

RESULTS

The 2647 records retrieved were reduced to 7 studies to be qualitatively assessed and 4 studies were included in the meta-analysis. RR of 1.88 [0.59, 5.95] of the pooled values pointed that recurrence rate after the conservative surgery is neither comparable nor lower than the radical surgery (P = 0.28).

CONCLUSIONS

Conservative surgery does not reduce the recurrence rate as efficiently as radical surgery for primary SMA. However, there is not enough evidence to support this statement.

Recurrent giant mandibular ameloblastoma in young adults

BACKGROUND

The purpose of the study was to define the most appropriate management of the giant mandibular ameloblastoma (GMA) in young adults.

METHODS

A retrospective study was performed on patients with GMA <30 years old. The data collected included initial treatment, tumor margins, reconstruction, and follow-up. Patients evaluated speech, chewing, swallowing, and facial appearance after definitive treatment.

RESULTS

Thirteen patients were identified with recurrent solid/multicystic disease requiring further treatment. Definitive treatment involved segmental mandibulectomy and reconstruction with free fibular flap in all patients. Seven patients had immediate reconstruction (group A) and 6 had secondary (group B). Mandibular resection was planned at least 2 cm beyond the radiological limit, free margins were achieved in all patients, and all flaps were transplanted successfully. In group A, functional score was 13.7 ± 0.45 and facial appearance score was 4.5 ± 0.49, whereas in group B were 11.16 ± 0.37 and 3.3 ± 0.5, respectively (both p < .05).

CONCLUSION

Aggressive resection of the GMA and immediate reconstruction is strongly advised. © 2015 Wiley Periodicals, Inc. Head Neck 38: E1947-E1954, 2016.

Treatment of recurrent mandibular ameloblastoma

Ameloblastoma is a locally invasive benign odontogenic tumor with a high rate of recurrence in the long term. The authors conducted a retrospective study of patients with mandibular ameloblastoma in order to evaluate recurrent ameloblastoma management. The study included data from 31 patients over a period of 10 years. Data collected included age, gender, tumor location, histological findings, initial treatment, number of recurrences and year of onset, type of treatment of recurrence, reconstruction and follow-up. Recurrences were detected in nine patients (29%). Tumor recurrences appeared at 32 months on average following the initial surgical procedure. Recurrences were associated mainly to inadequate initial therapeutic approach and were treated by bone resection with a safety margin of at least 1 cm beyond the radiographically visible margins. Immediate reconstruction of bone defects was performed with grafts or free flaps.

Recurrence of ameloblastoma in temporal area: primary treatment influences recurrence rate

Ameloblastomas are benign odontogenic tumors but are locally aggressive, most commonly occurring in the mandible and in the third to fifth decade of life. The male-to-female ratio is approximately equal. Recurrence of ameloblastoma due to inadequate treatment is often described. Recurrences in the temporal area are very rare and are related to the type of primary treatment. The authors describe a case of ameloblastoma recurrence in the temporal area and review the literature regarding recurrence and treatment.

Suppression of local invasion of ameloblastoma by inhibition of matrix metalloproteinase-2 in vitro

Background

Ameloblastomas are odontogenic neoplasms characterized by local invasiveness. This study was conducted to address the role of matrix metalloproteinase-2 (MMP-2) in the invasiveness of ameloblastomas.

Methods

Plasmids containing either MMP-2 siRNA or tissue inhibitor of metalloproteinase-2 (TIMP-2) cDNA were created and subsequently transfected into primary ameloblastoma cells. Zymography, RT-PCR, and Western blots were used to assess MMP-2 activity and expression of MMP-2 and TIMP-2, as well as protein levels.

Results

Primary cultures of ameloblastoma cells expressed cytokeratin (CK) 14 and 16, and MMP-2, but only weakly expressed CK18 and vimentin. MMP-2 mRNA and protein levels were significantly inhibited by RNA interference (P < 0.05). Both MMP-2 siRNA and TIMP-2 overexpression inhibited MMP-2 activity and the in vitro invasiveness of ameloblastoma.

Conclusion

These results indicate that inhibition of MMP-2 activity suppresses the local invasiveness of ameloblastoma cells. This mechanism may serve as a novel therapeutic target in ameloblastomas pursuant to additional research.

Vergleichende klinische und immunhistochemische Charakterisierung keratozystischer odontogener Tumoren und Ameloblastome im Hinblick auf das Rezidivrisiko

BACKGROUND

With the new term "keratocystic odontogenic tumour" (KCOT) keratocyts are even in the nomenclature a close differential diagnosis to ameloblastomas (A).

PURPOSE

Recurrence of KCOT and A were retrospectively compared with regard to treatment and immunohistochemical markers of cell cycle and migration and cell architecture.

PATIENTS AND METHODS

Biopsies harvested over a period of 22 years of 101 patients (86 KCOT, 15 A) were examined. The histopathological slides were stained with H&E and with the immunohistochemical markers: Cyclin D1, Collagen IV, p16, Cox-2-Laminin-5 and Tenascin-C.

RESULTS

Mean age KCOT 47 years (range 14-80 years), A 41 years (range 16-79 years). Gender KCOT: m:f =2:1; A: m:f = 3:2. Region of origin mandible with predilection of the angle and the ramus: KCOT: 76; A: 12. Maxilla: KCOT: 18; A: 3. Multiple lesions were found in 5 KCOT patients. Treatment primary KCOT: cystectomy (46), cystostomy (6), cystectomy and curettage (17), cystectomy and marginal ostectomy (14), resection (11). A: resection (10), enucleation (5). Recurrence rate KCOT: 11,7% after 5,5 years. Recurrence after: cystostomy (4), cystectomy (6), cystectomy and curettage (3), cystectomy and marginal ostectomy (2). A: no recurrences. Immunohistochemistry Cell cycle associated and extracellular matrix proteins did not differ in quantity in KCOT and A, and did also not differ in recurrent and non-recurrent KCOT.

CONCLUSIONS

1. KCOT are in the own cohort more likely recurrent than A. 2. Recurrence rate of KCOT can not be predicted by the used (most common) markers of cell cycle, migration and modulation of architecture. 3. Higher recurrence rate of KCOT in the patients examined is proposed due to less extensive resection.

Piezosurgical Treatment of Unicystic Ameloblastoma

BACKGROUND

This case report describes a 22-year-old female who was referred with a radiolucent lesion between her mandibular right molars. The original radiographic image suggested an odontogenic cyst.

METHODS

The surgical enucleation and osteotomy of the residual cavity were performed with a piezoelectric knife. Histologic analysis revealed the lesion was a unicystic ameloblastoma that showed no evidence of epithelial invasion in the connective tissue wall, and it appeared to be contained within the cystic cavity with an intraluminal projection showing features of an ameloblastoma. The patient refused any further surgical treatment. In consideration of the pathological result (no presence of invasive epithelial cells in the connective tissue wall of the cyst), a wait-and-see policy was proposed to the patient, with more extensive surgical treatment only if a recurrence was noted.

RESULTS

The patient has been followed clinically and radiographically at 6-month intervals for 5 years. There have been no signs of recurrence.

CONCLUSION

Therefore, the piezoelectric knife could be considered a promising device in the treatment of odontogenic tumors.

Recurrence related to treatment modalities of unicystic ameloblastoma: a systematic review

This systematic review aims to identify all studies pertinent to the clinical question, 'which treatment for unicystic ameloblastoma results in the lowest recurrence rate?' A structured systematic search of the literature, with predefined inclusion and exclusion criteria, using computer and manual searches as well as personal communication, was performed. Evaluations and critical appraisal were done separately in 3 rounds. All searches were performed by 2 independent judges and any disagreement was settled by discussion with a third party. Four treatment modalities for unicystic ameloblastomas were identified. The recurrence rates were 3.6% for resection, 30.5% for enucleation alone, 16% for enucleation followed by application of Carnoy's solution and 18% for marsupialization with/without other treatment in a second phase. It was concluded that there is only weak evidence showing that jaw resection resulted in the lowest recurrence rate, followed by enucleation with application of Carnoy's solution. Enucleation alone resulted in the highest recurrence rate and treatment by marsupialization cannot be sufficiently evaluated since most cases were followed by a second stage surgery of some kind.