Odontogenic myxoma--characterisation of the extracellular matrix (ECM) of the tumour stroma

Sinonasal Myxoma: A Distinct Entity or a Myxoid Variant of Desmoid Fibromatosis?

Sinonasal myxoma (SNM) is a rare benign mesenchymal tumor that arises in the sinonasal cavity or maxilla and almost exclusively affects young children. Currently, it is considered a specific entity, but its molecular characteristics have not been reported. Lesions diagnosed as SNM and odontogenic myxoma/fibromyxoma (OM/OFM) were identified from the participating institutions, and the clinicopathologic features were recorded. Immunohistochemistry for β-catenin was performed on all cases with available tissue. Next-generation sequencing (NGS) was performed on all SNM cases. Five patients with SNM were identified, including 3 boys and 2 girls with an age range of 20-36 months (mean: 26 months). The tumors were well-defined, centered in the maxillary sinus, surrounded by a rim of woven bone, and composed of a moderately cellular proliferation of spindle cells oriented in intersecting fascicles in a variably myxocollagenous stroma that contained extravasated erythrocytes. Histologically, the tumors resembled myxoid desmoid fibromatosis. Three tested cases showed nuclear expression of β-catenin. In 3 tumors, NGS revealed intragenic deletions of APC exons 5-6, 9 and 15, or 16, respectively, with concurrent loss of the other wild-type copy of APC, predicted to result in biallelic inactivation. The deletions were identical to those that occur in desmoid fibromatosis, and copy-number analysis raised the possibility that they were germline. In addition, one case showed possible deletion of APC exons 12-14, and another case exhibited a CTNNB1 p.S33C mutation. Ten patients with OM/OFM were identified, including 4 women and 6 men (mean age: 42 years). Seven tumors involved the mandible, and 3 the maxilla. Histologically, the tumors differed from SNM, and all cases lacked nuclear expression of β-catenin. These findings suggest that SNM represents a myxoid variant of desmoid fibromatosis that often arises in the maxilla. Because the APC alterations might be germline, genetic testing of the affected patients should be considered.

Evaluation of the osteoclastogenic process associated with RANK / RANK-L / OPG in odontogenic myxomas

BACKGROUND

Odontogenic myxoma (OM) is a benign intraosseous neoplasm that exhibits local aggressiveness and high recurrence rates. Osteoclastogenesis is an important phenomenon in the tumor growth of maxillary neoplasms. RANK (Receptor Activator of Nuclear Factor κappa B) is the signaling receptor of RANK-L (Receptor activator of nuclear factor kappa-Β ligand) that activates the osteoclasts. OPG (osteoprotegerin) is a decoy receptor for RANK-L that inhibits pro-osteoclastogenesis. The RANK / RANKL / OPG system participates in the regulation of osteolytic activity under normal conditions, and its alteration has been associated with greater bone destruction, and also with tumor growth.

OBJECTIVES

To analyze the immunohistochemical expression of OPG, RANK and RANK-L proteins in odontogenic myxomas (OMs) and their relationship with the tumor size.

MATERIAL AND METHODS

Eighteen OMs, 4 small (<3 cm) and 14 large (> 3cm) and 18 dental follicles (DF) that were included as control were studied by means of standard immunohistochemical procedure with RANK, RANKL and OPG antibodies. For the evaluation, 5 fields (40x) of representative areas of OM and DF were selected where the expression of each antibody was determined. Descriptive and comparative statistical analyses were performed with the obtained data.

RESULTS

There are significant differences in the expression of RANK in OM samples as compared to DF (p = 0.022) and among the OMSs and OMLs (p = 0.032). Also a strong association is recognized in the expression of RANK-L and OPG in OM samples.

CONCLUSIONS

Activation of the RANK / RANK-L / OPG triad seems to be involved in the mechanisms of bone balance and destruction, as well as associated with tumor growth in odontogenic myxomas.

Osteo-cementum Producing Odontogenic Myxomas. A Literature Review of a Distinctive Variant

INTRODUCTION

Odontogenic myxoma (OM) is a benign neoplasm of mesenchymal origin with growth characteristics, clinical behaviour and radiographic presentation similar to those of ameloblastoma. It is an intraosseous neoplasm characterized by stellate and spindleshaped cells embedded in loose myxoid or mucoid extracellular matrix. Although sometimes bony islands that represent residual trabeculae are found throughout the lesion, the formation of osteocement-like calcified spherules within the tumour is an extremely rare phenomenon.

REVIEW

We report a very rare case of an OM of the left maxilla exhibiting osteo-cementous metaplasia within the substance of the tumour and beyond the facial skeleton, in the nasopharynx. A review of all four similar cases previously reported in the literature is also presented.

CONCLUSION

Whether or not this property to produce significant amounts of bone can be associated with a different biological behavior for this specific variant of OM remains to be proved with the study of more similar cases.

Odontogenic Myxoma: a study based on biopsy material over a 40-year period

AIM

Odontogenic tumors, including odontogenic myxomas (OMs) are regarded as rare neoplasms in the human body. Nevertheless, they may be problematic for diagnosis and treatment planning due to possible variations between different races and countries. The aim of the current study was to present the clinicopathologic features of OM in an Iranian population over a 40-year period and compare them with those reported elsewhere.

MATERIALS AND METHODS

Clinical/demographic data and histologic slides of OMs and all lesions that could be considered in their differential diagnosis, reported from 1967-2008 were analyzed. Statistical analysis was performed using χ(2) and t-test and p < 0.05 was regarded significant.

RESULTS

Forty OMs were identified, of which 42.5% occurred in men (mean age, 27.4 years) and 57.5% in women (mean age, 28.2 years). Most tumors were observed in the posterior mandible. All cases possessed the classic World Health Organization histologic features; while 3, 15 and 6 cases showed epithelial rests, residual bone and conspicuous collagen bundles, respectively. Five patients were followed and none of their tumors recurred.

CONCLUSION

The clinicopathologic characteristics of the current Iranian population are similar to most other reports with a predilection for the posterior mandible, 3rd decade and female subjects; however, there were variations in microscopic features of the studied cases. Clinical significance: Clinical and histologic information on OM in different populations may be useful in clinical settings and treatment planning. Reporting more detailed histologic data can help clarify the biology of this tumor and aid in its histopathologic diagnosis. i

Unusual presentation of localized gingival enlargement associated with a slow-growing odontogenic myxoma

Unusual presentation of localized gingival enlargement associated with a subjacent tumoural pathology is reported. The patient was a 55-year-old black male, whose chief complaint was a progressive gingival overgrowth for more than ten years, in the buccal area of the anterior left mandible. According to the clinical features and the radiological diagnosis of odontogenic keratocyst, a conservative surgery with enucleation and curettage was performed. Tissue submitted for histopathological analysis rendered the diagnosis of odontogenic myxoma. After 12-month of follow-up, no evidence of recurrence was found. Clinicians should be cautious when facing any gingival enlargement to avoid diagnostic pitfalls and to indicate the appropriate treatment.

The orosomucoid 1 protein (α1 acid glycoprotein) is overexpressed in odontogenic myxoma

BACKGROUND

Odontogenic myxoma (OM) is a benign, but locally invasive, neoplasm occurring in the jaws. However, the molecules implicated in its development are unknown. OM as well as Dental Follicle (DF), an odontogenic tissue surrounding the enamel organ, is derived from ectomesenchymal/mesencyhmal elements. To identify some protein that could participate in the development of this neoplasm, total proteins from OM were separated by two-dimensional electrophoresis and the profiles were compared with those obtained from DF, used as a control.

RESULTS

We identified eight proteins with differential expression; two of them were downregulated and six upregulated in OM. A spot consistently overexpressed in odontogenic myxoma, with a molecular weight of 44-kDa and a pI of 3.5 was identified as the orosomucoid 1 protein. Western blot experiments confirmed the overexpression of this protein in odontogenic myxoma and immunohistochemical assays showed that this protein was mainly located in the cytoplasm of stellate and spindle-shaped cells of this neoplasm.

CONCLUSION

Orosomucoid 1, which belongs to a group of acute-phase proteins, may play a role in the modulation of the immune system and possibly it influences the development of OM.

A case of odontogenic myxoma with unusual histological features mimicking a fibro-osseous process

Odontogenic myxoma is a rare benign but locally aggressive odontogenic tumor. This report describes a case of odontogenic myxoma producing diffusely dispersed calcified products in a pattern reminiscent of a fibro-osseous lesion of the jaw. Differential diagnoses for myxoid lesions of the jaws also are discussed. This paper highlights how an odontogenic myxoma can produce a large amount of calcified products to mimic a fibro-osseous process.

Odontogenic myxoma: clinico-pathological, immunohistochemical and ultrastructural findings of a multicentric series

The aim of this study was to analyze the clinico-pathological and immunohistochemical features of 62 cases of odontogenic myxoma (OM) diagnosed in three Oral Pathology Diagnostic Services in Latin America, as well as to describe the ultrastructural features of three of these cases. OM showed a wide age range (9-71 years), with a mean of 27.97 yr (SD: 11.01) and a male to female ratio of 1:2.2. Mandible was affected in 37 cases (59.6%) and maxilla in 25 (40.4%), with 61.3% located in the posterior region. Thirty-nine cases (62.9%) were multilocular and 23 (37.1%) unilocular. Size ranged from 1 to 13 cm, (mean: 5.2 cm). Thirty-seven multilocular (54.8%) and 6 unilocular lesions (26%) were larger than 4 cm (p<0.05). Epithelial islands were identified in 5 cases (8%) on H&E stained sections, but AE1/AE3 and CK14 disclosed these structures in 15 cases each (24.2%); CK5 was positive in 8 (12.9%); CK7 in 2 (3.2%) and CK19 in only 3 cases (4.8%). All cases were negative for CKs 8 and 18, S-100 protein, NSE and CD68, and showed a low index of expression of Bcl2 and ki-67 proteins (<1%). Mast cell antibodies showed these cells in 45 cases (72.6%). Myofibroblastic differentiation evidenced by myofilaments and fibronexi was found in one case out of the three studied by TEM and 29 cases (46.7%) were positive by immunohistochemistry for alpha actin. In conclusion, only a minority of OM had epithelial islands, and only 3 cases expressed CK 19, indicating an odontogenic epithelium origin. Immunohistochemical and ultrastructural findings suggest that OM is a mesenchymal neoplasm in which several factors may contribute to its pathogenesis, including myofibroblastic differentiation and the participation of mast cell products. However, further investigations are needed to better understand the participation of these elements in this particular neoplasm.

The expression of apoptotic proteins and matrix metalloproteinases in odontogenic myxomas

PURPOSE

The odontogenic myxoma is a rare benign tumor affecting the jaws. We hypothesize that odontogenic myxomas have dysregulated antiapoptotic mechanisms to assist in neoplastic growth. We believe that antiapoptotic proteins of the Bcl-2 family are over expressed and that tumor cells must generate some form of matrix proteinase. The aim of this study was to evaluate odontogenic myxomas for the expression of cell cycle protein Ki-67, apoptosis-regulating proteins Bcl-2, Bcl-XL, Bak, and Bax, and matrix metalloproteinases MMP-2, MMP-3, and MMP-9.

MATERIALS AND METHODS

Odontogenic myxomas submitted to oral pathology between 1974 and 1998 were evaluated. Twenty-six paraffin-embedded tissue sections were used in a standard immunohistochemistry protocol and incubated with one of the following antibodies: Bcl-2, Bcl-XL, Bak, Bax, or Ki-67. The sections were then incubated with anti-immunoglobulin conjugated to peroxidase-labeled dextran polymer in a Tris-HCl buffer. Counts of positive (staining) cells were completed in 5 high-power fields for each specimen. Each slide was reviewed by 2 investigators, and final data were pooled and averaged.

RESULTS

Specimen slides showed an increase in cells staining positively for anti-apoptotic proteins Bcl-2 and Bcl-X. An average of 6.5% of specimen cells were positive for Bcl-2 and 10.4% for Bcl-X. Control tissue showed only 1.1% of cells to be positive for Bcl-2 and 1.2% for Bcl-X. Less than 1% of both specimen and control cells stained positively for Ki-67. Proapoptotic proteins (Bak and Bax) were not detected in tumor cells. Ninety percent of tumor cells stained positively for MMP-2 compared with 10% of controls. Specimen and controls were negative for MMP-3 and MMP-9.

CONCLUSION

Odontogenic myxoma tumor cells did not show an increase in cell division. Less than 1% of tumor and control cells were positive for Ki-67. Odontogenic myxoma tumor cells showed increased expression of antiapoptotic proteins (Bcl-2 and Bcl-X) and the matrix metalloproteinase MMP-2. This study suggests that 2 mechanisms of disease progression used by the odontogenic myxoma are the production of antiapoptotic proteins and the secretion of matrix metalloproteinases.

Diagnostic imaging for a case of maxillary myxoma with a review of the magnetic resonance images of myxoid lesions

The findings of conventional radiography, computed tomography, and magnetic resonance imaging are reported for an odontogenic myxoma arising in the left anterior maxilla of a 50-year-old man. The magnetic resonance imaging characteristics of an intraosseous myxoma are described for the first time. The initial conventional radiographic examination disclosed a unilocular radiolucency with poorly delineated margins as typically seen in malignant tumors. Subsequently, acquired computed tomography scans displayed bony expansion and thinning of cortices on the labial aspect of the lesion. Magnetic resonance imaging revealed a well-defined, well-enhanced mass lesion with homogeneous signal intensity on every pulse sequence. The lesion showed intermediate signal intensity on the T1- and T2-weighted images. Magnetic resonance imaging of the present maxillary myxoma revealed a higher signal intensity on T1-weighted and a lower signal intensity on T2-weighted images than for previously reported myxomas of the soft tissues. This discrepancy might be related to the viscosity of the mucoid substance or the protein density of the tumor.