Cytogenetic abnormalities in an ossifying fibroma from a patient with bilateral retinoblastoma

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. 

Parafibromin Abnormalities in Ossifying Fibroma

Ossifying fibromas are very rare tumors that are sometimes seen as part of the hyperparathyroidism-jaw tumor syndrome (HPT-JT), which is caused by inactivating mutations of the HRPT2/CDC73 tumor suppressor gene. CDC73 mutations have been identified in a subset of sporadic cases but aberrant expression of the encoded protein, parafibromin, has not been demonstrated in ossifying fibroma. We sought to determine if loss of parafibromin regularly contributes to the development of sporadic, nonsyndromic ossifying fibroma. We examined a series of 9 ossifying fibromas, including ossifying, cemento-ossifying, and juvenile active variants, for parafibromin protein expression by immunohistochemistry and for CDC73 sequence abnormalities by Sanger sequencing and/or targeted AmpliSeq panel sequencing. Four ossifying fibromas showed a complete absence of nuclear parafibromin expression; loss of parafibromin expression was coupled with aberrant cytoplasmic parafibromin expression in 1 case. CDC73 mutations were detected in 2 cases with aberrant parafibromin expression. These results provide novel evidence, at the level of protein expression, that loss of the parathyroid CDC73/parafibromin tumor suppressor may play a role in the pathogenesis of a subset of ossifying fibromas.

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.

[Benign fibro-osseous tumors of the frontal skull base with intracranial extension. Report of 2 cases]

We report on two patients with ossifying fibroma of the anterior skull base with intracranial extension. A psammomatoid ossifying fibroma was removed from a 29 year old female patient, and in a 37 year old female patient a cemento ossifying fibroma was removed. The main clinical symptom in both cases was headache. Surgery took place after diagnosis and therapy in an interdisciplinary operation with ENT colleagues. The ossifying fibroma is a benign neoplasm mainly affecting the maxilla and mandible. Complete removal is better than a curettage of the tumor.

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

Benign fibro-osseous lesions of bone (BFOL) comprise a group of clinically distinct entities with significant histologic overlap and often occur in children and adolescents. Because of prior studies indicating that these lesions possess distinct karyotypic abnormalities, we conducted a retrospective review of cytogenetic analyses performed in a series of 16 BFOL in children and adolescents diagnosed at two institutions. These comprised five cases with the diagnosis of ossifying fibroma, four with osteofibrous dysplasia, and seven with fibrous dysplasia arising in the skeleton of 16 children and adolescents. All cases were analyzed using standard G-banding techniques on fresh tumors explanted in tissue culture media. Spectral karyotyping (SKY) and fluorescence in situ hybridization (FISH) were used to analyze selected metaphases of a talar lesion with the histologic features of ossifying fibroma. All four confirmed ossifying fibromas, including the talar lesion, contained clonal aberrations fusing breakpoints on Xq26 and 2q33, and one case with dissimilar histology did not. Three of four osteofibrous dysplasias contained multiple copies of chromosomes 8, 12, and/or 21. All but two fibrous dysplasia cases exhibited either a completely normal karyotype or single cell aberrations. One fibrous dysplasia had subtle chromosomal abnormalities not seen in other cases in the series, and another had complex abnormalities involving multiple chromosomes. Our current and published results indicate that cytogenetics might be of ancillary use in the diagnosis of BFOL and that a characteristic chromosomal arrangement is associated with ossifying fibroma.

Benign fibro-osseous lesions: a review of current concepts

The benign fibro-osseous lesions (BFOL) represent a clinically diverse group of disorders of bone that share similar histopathologic features. As a group, they are relatively common in the craniofacial complex, especially the jaws. Although the general concept of BFOL is relatively well known, specific diagnostic interpretation of individual cases is often challenging. New concepts and controversies have arisen over the past 10 to 15 years regarding classification and diagnostic criteria. However, among the new theories and contentions, there is now essential agreement that the osseous dysplasias represent a single disease process, while the so-called "juvenile active ossifying fibroma" and other "aggressive," "active," "psammomatoid" ossifying/cementifying fibromas remain controversial. This review is presented to update the surgical pathologist on the various entities comprising the spectrum of BFOL and to examine the criteria for their diagnosis.

Multiple acral fibromas in a patient with familial retinoblastoma: a cutaneous marker of tumour-suppressor gene germline mutation?

We report a 40-year-old patient with familial retinoblastoma also affecting his elder son, who developed multiple fibromas on the periungual or subungual areas of all the fingers. Molecular analysis disclosed a loss of heterozygosity for the RB1 gene in the larger tumour, with disappearance of the normal allele and persistence of the mutated allele only. The similarity of this observation with distal fibrous tumours encountered in other diseases with germline mutations of tumour-suppressor genes such as neurofibromatosis type 1, tuberous sclerosis and multiple endocrine neoplasia type 1 led to the hypothesis that multiple acral benign tumours with a fibrous component might be a cutaneous marker of tumour suppressor gene germline mutation with low sensitivity but high specificity.

Infant cardiac fibroma with clonal t(1;9)(q32;q22) and review of benign fibrous tissue cytogenetics

Cardiac fibromas are rare lesions which occur more frequently in infants and children than in the adult population. These tumors are nonmalignant proliferations of connective tissue most often found in the left ventricular myocardium or septal myocardium. No cytogenetic studies of cardiac fibromas have been reported. We report a case of an infant with a subepicardial tumor in whom the cytogenetic analysis showed a clonal reciprocal translocation, 46,XY,t(1;9)(q32;q22),inv(9)(p11q12)c. We review the literature regarding cardiac fibromas and briefly discuss the cytogenetics of benign fibrous neoplasias.

Nonrandom chromosome breakpoints at Xq26 and 2q33 characterize cemento-ossifying fibromas of the orbit

BACKGROUND

Cytogenetic reports of histologically benign fibroosseous lesions are rare, with only nine previously reported cases. None of these previous studies revealed consistent numerical or structural chromosome aberrations, and to the authors' knowledge, no karyotypic abnormalities in cemento-ossifying fibromas of the orbit have been reported.

METHODS

Short term in situ culture and Giesma-band chromosome methods were used to analyze three cementifying fibromas of the orbit: one from a 13-year-old African American male, one from a 14-year-old Hispanic male, and one from a 17-year-old white male.

RESULTS

Cytogenetic findings in these three cases revealed the presence of identical chromosomal breakpoints occurring in all three tumors at bands Xq26 and 2q33. Two of the tumors showed an identical t(X;2)(q26;q33) reciprocal translocation as the sole abnormality. The third tumor revealed an interstitial insertion of bands 2q24.2q33 into Xq26 as the sole abnormality.

CONCLUSIONS

The authors described new nonrandom breakpoints in fibroosseous lesions of the orbit, which can result from at least two different types of structural chromosomal aberrations. The identification of recurring breakpoints at Xq26 and 2q33 provides a new cytogenetic tumor marker for the identification of this tumor subtype. The sublocalization of breakpoints in this tumor should provide important information for the precise localization and characterization of genes involved in the histiogenesis of these lesions.

Cytogenetics of tumors of soft tissue and bone. Implication for pathology

Pathologists should be aware of the existence of diagnostically useful chromosomal rearrangements in several soft tissue and bone tumors. They include rearrangement of 8q12 in lipoblastomas, ring chromosomes in atypical lipomas, ring and giant marker chromosomes in well differentiated liposarcomas, t(12;16)(q13;p11) in myxoid liposarcomas, rearrangement of 7p21-22 in low-grade endometrial stromal sarcomas, t(2;13)(q37;q14) in alveolar rhabdomyosarcomas, t(X;18)(p11.2;q11.2) in synovial sarcomas, t(12;22) (q13;q13) in clear cell sarcomas, t(11;22)(q24;q12) in Ewing's sarcomas and peripheral neuroepitheliomas, and t(9;22)(q21-31;q11-12) in extraskeletal myxoid chondrosarcomas.

Chromosome aberrations in fibrous dysplasia

We report the cytogenetic findings of two cases of fibrous dysplasia, one occurring in the tibia, the other in the sphenoid. Both cases exhibited only one chromosome change: a t(6;11)(q15;p15) in the first case, a derivative chromosome 2 in the second. The previous cytogenetic report on fibrous dysplasia revealed only numerical changes. The significance of these inconsistent chromosomal findings in fibrous dysplasia is unclear.

Cytogenetics of cranial base tumors

Many different tumor types can arise in or invade the skull base. The more common tumors include, but are not limited to, angiofibromas, chondrosarcomas, chordomas, hemangiopericytomas, meningiomas, carcinomas, olfactory neuroblastomas, paragangliomas, pituitary adenomas, and rhabdomyosarcomas. Several of these tumors, including meningiomas, hemangiopericytomas, and rhabdomyosarcomas are characterized by nonrandom cytogenetic abnormalities. In this paper, we review the recognized chromosomal aberrations in cranial base tumors and illustrate the insights that can be gained into the genetic basis of tumor formation using karyotypes from skull base tumors that we have examined. As in tumors in other locations, chromosomal findings may be of diagnostic and prognostic value in cranial base tumors.

Chromosome abnormalities in cementifying fibroma

Cementifying fibroma is the most frequent benign fibro-osseous odontogenic tumor. We found chromosome abnormalities in a second case of this type of benign tumor. The chromosome changes in both cases are different. The chromosome bands involved in our case have not been described before in any benign fibroma so far reported.