Ameloblastic Fibrosarcoma of the mandible evolving from a prior Ameloblastic Fibroma after two years: an unusual finding

Odontogenic sarcoma: First report after new who nomenclature with systematic review

Ameloblastic fibrosarcoma (AFS) now designated as odontogenic sarcoma is a malignant odontogenic tumor characteristically composed of a benign epithelium and a malignant mesenchymal component. It can arise de novo without any preexisting lesion or it can result from the malignant transformation of ameloblastic fibroma (AF). Hereby, we report an extremely rare case of odontogenic sarcoma which was transformed from AF over a period of about 2 years. This is the first case to be reported after it has been reclassified as odontogenic sarcoma. A systematic review was also done to evaluate the studies that reported AFS arising de novo and AFS arising from AF. The objective of this study is to systematically review the studies that reported AFS arising de novo and AFS arising from AF. Articles that reported AFS arising de novo and AFS arising from AF were collected from PubMed, Medline, Embase, Cochrane, Google search and manual search. The results of the systematic review showed that six studies (46.1%) reported AFS arised de novo with no previous history of AF. Seven studies (53.84%) reported that amelobastic fibrosarcoma arised from AF. A rare case of odontogenic sarcoma transformed from AF is reported here. This is the first case report to be published on odontogenic sarcoma after the World Health Organization reclassification. AF once diagnosed should be treated immediately without any delay to avoid the chances of its malignant transformation into odontogenic sarcoma.

[BRAF gene mutations in ameloblastic fibromas]

OBJECTIVE

To investigate the BRAF gene mutations in ameloblastic fibroma (AF), and to further analyze the relationship between the BRAF mutation and clinical characteristics so as to provide new reference to the study of AF's molecular pathology.

METHODS

Sixteen cases diagnosed as AF at the Department of Oral Pathology, Peking University School of Stomatology between January 1990 and December 2017 were collected. Genomic DNA was extracted from formalin-fixed, paraffin embedded tissues using the QIAamp DNA Mini Kit (Qiagen, Germany) according to the manufacturer's instructions. Polymerase chain reaction (PCR) and direct sequencings were used to detect the BRAF gene mutations. The clinicopathological data, such as the age, location of the lesion, symptoms and treatments were retrospectively analyzed.

RESULTS

The sixteen cases of AF involved nine women and seven men aged 2-67 years. Three lesions occurred in the maxilla and thirteen in the mandible. The most common presenting symptom of AF was a painless slowly enlarging mass with swelling. Ten patients received conservative treatment and the other six patients received radical surgery. Three cases relapsed during the study period. BRAF gene mutation was found in sixteen of all the sixteen samples analyzed (100%). The BRAF mutation was a point mutation with a thymine-adenine transversion at nucleotide 1 799 of 15 exons, resulting in a change at residue 600 that substituted glutamine for valine. This mutation was the strongest activator of the downstream RAS/RAF/MEK/ERK-MAPK signaling pathway. This helped to bring about a gain-of-function mutation due to a V600E substitution. Many studies identified that BRAF regulated survival, apoptosis, and proliferation of cells by inducing MAPK pathways activation. For the existing cases, none of the age, sex, location, recurrence and treatments had a statistically significant correlation with BRAF mutation.

CONCLUSION

Our findings demonstrated high prevalence of BRAF V600E mutation in AF. The pathogenic role remains to be clarified．.

Odontogenic tumors: where are we in 2017 ?

Odontogenic tumors are a heterogeneous group of lesions of diverse clinical behavior and histopathologic types, ranging from hamartomatous lesions to malignancy. Because odontogenic tumors arise from the tissues which make our teeth, they are unique to the jaws, and by extension almost unique to dentistry. Odontogenic tumors, as in normal odontogenesis, are capable of inductive interactions between odontogenic ectomesenchyme and epithelium, and the classification of odontogenic tumors is essentially based on this interaction. The last update of these tumors was published in early 2017. According to this classification, benign odontogenic tumors are classified as follows: Epithelial, mesenchymal (ectomesenchymal), or mixed depending on which component of the tooth germ gives rise to the neoplasm. Malignant odontogenic tumors are quite rare and named similarly according to whether the epithelial or mesenchymal or both components is malignant. The goal of this review is to discuss the updated changes to odontogenic tumors and to review the more common types with clinical and radiological illustrations.