Cytogenetic distinction among benign fibro-osseous lesions of bone in children and adolescents: value of karyotypic findings in differential diagnosis

Psammomatoid Ossifying Fibroma Is Defined by SATB2 Rearrangement

Psammomatoid ossifying fibroma (PsOF), also known as juvenile PsOF, is a benign fibro-osseous neoplasm predominantly affecting the extragnathic bones, particularly the frontal and ethmoid bones, with a preference for adolescents and young adults. The clinical and morphologic features of PsOF may overlap with those of other fibro-osseous lesions, and additional molecular markers would help increase diagnostic accuracy. Because identical chromosomal breakpoints at bands Xq26 and 2q33 have been described in 3 cases of PsOF located in the orbita, we aimed to identify the exact genes involved in these chromosomal breakpoints and determine their frequency in PsOF using transcriptome sequencing and fluorescence in situ hybridization (FISH). We performed whole RNA transcriptome sequencing on frozen tissue in 2 PsOF index cases and identified a fusion transcript involving SATB2, located on chromosome 2q33.1, and AL513487.1, located on chromosome Xq26, in one of the cases. The fusion was validated using reverse transcription (RT)-PCR and SATB2 FISH. The fusion lead to a truncated protein product losing most of the functional domains. Subsequently, we analyzed an additional 24 juvenile PsOFs, 8 juvenile trabecular ossifying fibromas (JTOFs), and 11 cemento-ossifying fibromas (COFs) for SATB2 using FISH and found evidence of SATB2 gene rearrangements in 58% (7 of 12) of the evaluable PsOF cases but not in any of the evaluable JTOF (n = 7) and COF (n = 7) cases. A combination of SATB2 immunofluorescence and a 2-color SATB2 FISH in our index case revealed that most tumor cells harboring the rearrangement lacked SATB2 expression. Using immunohistochemistry, 65% of PsOF, 100% of JTOF, and 100% of COF cases showed moderate or strong staining for SATB2. In these cases, we observed a mosaic pattern of expression with >25% of the spindle cells in between the bone matrix, with osteoblasts and osteocytes being positive for SATB2. Interestingly, 35% (8 of 23) of PsOFs, in contrast to JTOFs and COFs, showed SATB2 expression in <5% of cells. To our knowledge, this is the first report that shows the involvement of SATB2 in the development of a neoplastic lesion. In this study, we have showed that SATB2 rearrangement is a recurrent molecular alteration that appears to be highly specific for PsOF. Our findings support that PsOF is not only morphologically and clinically but also genetically distinct from JTOF and COF.

First presentation of a frameshift mutation in the SETD2 gene of a juvenile psammomatoid ossifying fibroma (JPOF) associated with an aneurysmal bone cyst

Background

The rarity of juvenile psammomatoid ossifying fibroma (JPOF) and lack of cytogenetic studies prompted us to report a novel SETD2 gene mutation in a benign odontogenic tumour.

Case presentation

A 21-year-old man presented with a hard, expanded mandibular cortex. Computed tomography revealed multilocular radiopacity in the mandible; this was reconstructed via segmental mandibulectomy using a vascularised iliac crest flap. Based on the clinical and histological findings, we diagnosed JPOF associated with an aneurysmal bone cyst. Microscopically, the solid area was characterised by many rounded or angular ossicles in a cellular fibrous stroma. The stromal cells were spindle-like or stellate. Next-generation sequencing detected a frame shift mutation of the SETD2 gene, while the copy number was normal.

Conclusions

Our findings suggest further genetic studies should be performed to assess whether this mutation is related to tumour genesis. 

Molecular findings in maxillofacial bone tumours and its diagnostic value

According to the WHO, mesenchymal tumours of the maxillofacial bones are subdivided in benign and malignant maxillofacial bone and cartilage tumours, fibro-osseous and osteochondromatous lesions as well as giant cell lesions and bone cysts. The histology always needs to be evaluated considering also the clinical and radiological context which remains an important cornerstone in the classification of these lesions. Nevertheless, the diagnosis of maxillofacial bone tumours is often challenging for radiologists as well as pathologists, while an accurate diagnosis is essential for adequate clinical decision-making. The integration of new molecular markers in a multidisciplinary diagnostic approach may not only increase the diagnostic accuracy but potentially also identify new druggable targets for precision medicine. The current review provides an overview of the clinicopathological and molecular findings in maxillofacial bone tumours and discusses the diagnostic value of these genetic aberrations.

Central Cemento-Ossifying Fibroma: Primary Odontogenic or Osseous Neoplasm?

Currently, central cemento-ossifying fibroma is classified by the World Health Organization as a primary bone-forming tumor of the jaws. However, histopathologically, it is often indistinguishable from cemento-osseous dysplasias in that it forms osteoid and cementicles (cementum droplets) in varying proportions. It is believed that pluripotent cells within the periodontal membrane can be stimulated to produce either osteoid or woven bone and cementicles when stimulated. If this is true, cemento-ossifying fibroma would be better classified as a primary odontogenic neoplasm arising from the periodontal ligament. Cemento-ossifying fibromas also do not occur in the long bones. The present report compares several entities that fall within the diagnostic realm of benign fibro-osseous lesions and reviews the evidence for reclassifying central cemento-ossifying fibroma as a primary odontogenic neoplasm.

Management and Treatment Outcomes of Maxillofacial Fibro-osseous Lesions: A Retrospective Study

INTRODUCTION

Fibro-osseous lesions are a diverse group of bone disorders and include developmental, reactive or dysplastic diseases and neoplasms. They share overlapping clinical, radiographic and histopathologic features and demonstrate a wide range of biological behaviour.

AIM

To evaluate the characteristics, treatment and outcome of benign fibro-osseous lesions of the jaws.

PATIENTS AND METHOD

All patients with fibro-osseous lesions of the jaws treated at the department of Oral and Maxillofacial Surgery of the Kamineni Institute of Dental Sciences from 2007 to 2013 were included in this study.

RESULTS

Six males and four females were treated. Juvenile ossifying fibroma was most often encountered (40 %), and the mandible was the most frequent location (70 %). Main clinical feature in most of the cases was a painless expansile swelling with facial asymmetry, and radiologically mixed (radiolucent and radiopaque lesions) were seen in majority of cases. All cases were surgically treated and histopathologically confirmed. Segmental ostectomy was performed in six cases; maxillectomy was done in one case and excision along with margin in three cases. Mean follow-up was of 3.3 years with no recurrence.

CONCLUSIONS

Fibro-osseous lesions, although sharing similar microscopic features, exhibit a variety of clinical behavior rendering their treatment highly individualized. Radical treatment is the choice to achieve an outcome without recurrence.

Chromosome 12 long arm rearrangement covering MDM2 and RASAL1 is associated with aggressive craniofacial juvenile ossifying fibroma and extracranial psammomatoid fibro-osseous lesions

To evaluate the diagnostic value of MDM2 status in craniofacial fibro-osseous lesions, we investigated MDM2 expression by immunohistochemistry and analyzed MDM2 amplification by qPCR in 30 cases of ossifying fibroma (including 13 cases of the juvenile variant) and 17 cases of fibrous dysplasia. Two cases of uncommon extragnathic psammomatoid fibrous dysplasia and a mixed control group of 15 cases of low-grade osteosarcoma and 15 cases of well-differentiated/dedifferentiated liposarcoma were included. MDM2 amplification was found in 33% of ossifying fibromas (peak of 69% for the juvenile variant) and in 12% of fibrous dysplasia, in none of which was MDM2 overexpressed. All control cases exhibited MDM2 amplification and overexpression. To investigate possible polysomy of chromosome 12, we studied RASAL1 amplification, a gene telomeric to MDM2 on the long arm of chromosome 12. RASAL1 amplification was reported in all benign fibro-osseous lesions exhibiting MDM2 amplification but not in controls. Simultaneous amplification of these two genes was significantly higher in juvenile ossifying fibromas compared with fibrous dysplasia (P=0.004), non-juvenile ossifying fibromas (P=0.001), and all other benign craniofacial fibro-osseous lesions combined (P=0.0001). Of the nine cases of juvenile ossifying fibroma exhibiting amplification, three were locally invasive and four were recurrent, suggesting aggressive disease. The two cases of extragnathic psammomatoid fibrous dysplasia also showed MDM2 and RASAL1 amplification with no MDM2 overexpression. This large chromosome 12 rearrangement, spanning MDM2 and RASAL1, is the first recurrent molecular abnormality to be reported in juvenile ossifying fibroma. It may represent both a molecular diagnostic marker and a characteristic of more aggressive forms with a higher risk of recurrence. Finally, the presence of this rearrangement in extragnathic psammomatoid fibro-osseous lesions mimicking ossifying fibromas might reflect a common molecular pathway in their pathogenesis and calls into question the classification of such lesions within fibrous dysplasia.

Fibro-Osseous Lesions

This article describes the clinical, radiographic, gross, microscopic, and histologic features; differential diagnosis; molecular pathology; treatment; and prognosis of fibrous dysplasia, osteofibrous dysplasia, and adamantinoma of long bones.

Is there a link between osteofibrous dysplasia and adamantinoma?

Because of the relative frequency of osteofibrous dysplasia (OFD) and the gravity of adamantinoma, it is important to know whether there is a link between these two entities. A young boy had been followed from the age of 5 years for OFD of the right tibia. At the age of 10, biopsy performed because of pain, revealed OFD-like adamantinoma. Surgery was undertaken, with en bloc proximal tibial resection of 14 cm and reconstruction by free vascularized fibula and internal fixation. This observation illustrates the risk of evolution of OFD-like adamantinoma, showing the same unfavorable evolution as classic adamantinoma. Strict surveillance is mandatory in OFD, with systematic biopsy in case of onset of pain or increased tumor volume.

Osteofibrous dysplasia and adamantinoma in children and adolescents: a clinicopathologic reappraisal

Osteofibrous dysplasia (OFD) and adamantinoma are rare and most commonly arise in the tibia of young individuals. Although OFD has typical histopathologic features, areas resembling OFD have often been noted at the periphery of otherwise classic adamantinomas, and some have suggested that OFD may be either a precursor to or a regressive phase of adamantinoma. The so-called OFD-like adamantinoma encompasses some features of both OFD and adamantinoma. We studied the clinical, imaging, histopathologic, immunohistochemical, ultrastructural, and molecular features of 16 OFD and 8 adamantinomas (5 OFD-like and 3 classic) in an attempt to further define their morphology, clinical course, and relationship. Patients with OFD were generally younger than those with adamantinoma. Osteoblastic and osteoclastic activity was more prominent in OFD than in OFD-like adamantinoma. In addition to the inconspicuous small clusters of epithelial cells in OFD-like adamantinoma, isolated keratin-positive cells with a unique ultrastructural hybrid fibroblastic-epithelial phenotype were found in the stroma of all OFD and OFD-like adamantinomas. Fluorescence in situ hybridization analysis revealed trisomies 7, 8, and/or 12 in the spindle cell stroma of OFD, OFD-like, and classic adamantinoma, supporting a neoplastic origin of OFD and a common histogenesis for all 3 lesions. Trisomies were not observed in osteoblasts or osteoclasts suggesting that the osseous component is reactive and non-neoplastic. Of the 11 OFD patients with follow-up (median, 4.5 y), all 3 who underwent incisional biopsy had persistent, nonprogressive disease and 2 of 8 who underwent curettage or wide excision had recurrence; none developed adamantinoma. All 6 adamantinoma patients with follow-up (3 classic and 3 OFD-like) were treated with wide excision. One with classic adamantinoma died of pulmonary metastases 9 years after presentation; the other 5 were free of disease with a median follow-up of 12 years. None of the classic adamantinomas evolved into OFD-like adamantinoma or OFD. Although the histopathology, immunohistochemistry, ultrastructure, and cytogenetics indicate that these lesions are closely related, our data and the literature suggest that only classic adamantinoma has malignant potential. OFD, OFD-like adamantinoma, and classic adamantinoma appear to show a progressive complexity of cytogenetic aberrations, perhaps indicative of a multistep neoplastic transformation.

Spectral karyotyping of human, mouse, rat and ape chromosomes--applications for genetic diagnostics and research

Spectral karyotyping (SKY) is a widely used methodology to identify genetic aberrations. Multicolor fluorescence in situ hybridization using chromosome painting probes in individual colors for all metaphase chromosomes at once is combined with a unique spectral measurement and analysis system to automatically classify normal and aberrant chromosomes. Based on countless studies and investigations in many laboratories worldwide, numerous new chromosome translocations and other aberrations have been identified in clinical and tumor cytogenetics. Thus, gene identification studies have been facilitated resulting in the dissection of tumor development and progression. For example, different translocation partners of the TEL/ETV6 transcription factor that is specially required for hematopoiesis within the bone marrow were identified. Also, the correct classification of complex karyotypes of solid tumors supports the prognostication of cancer patients. Important accomplishments for patients with genetic diseases, leukemias and lymphomas, mesenchymal tumors and solid cancers are summarized and exemplified. Furthermore, studies of disease mechanisms such as centromeric DNA breakage, DNA double strand break repair, telomere shortening and radiation-induced neoplastic transformation have been accompanied by SKY analyses. Besides the hybridization of human chromosomes, mouse karyotyping has also contributed to the comprehensive characterization of mouse models of human disease and for gene therapy studies.

Previously unidentified complex cytogenetic changes found in a pediatric case of solid-pseudopapillary neoplasm of the pancreas

Solid pseudopapillary neoplasm of the pancreas (SPNP) is a rare tumor with low malignant potential found in adolescent girls and young women. The pathogenesis of SPNP remains uncertain and its management is controversial. Genetic changes associated with SPNP have seldom been reported. We describe here the cytogenetic investigation of a case of SPNP in a 13-year-old girl whose tumor cells revealed two unrelated clones: one clone characterized by complex karyotypic changes, including breakpoints in two common fragile sites at chromosome 2, band q33, and chromosome 4, band q31, and the second clone defined by partial monosomy for chromosome X. Loss of heterozygosity for HRAS was also identified by array comparative genomic hybridization (a-CGH). These cumulative changes seem insufficient for activation of cell transformation, but could possibly play a role in priming the cell for future mutagenic events.