[Clinical, imaging and pathological and molecular characteristics of simple bone cyst]

Objective: To investigate the radiologic, pathologic, and molecular features of simple bone cysts (SBC), and their differential diagnoses. Methods: Fourteen cases of SBC were collected at the Department of Pathology, the First Affiliated Hospital of Nanjing Medical University from 2017 to 2022, and fluorescence in situ hybridization (FISH) was performed for retrospective analysis. Results: There were 14 patients, including 7 females and 7 males, with age range of 7 to 45 (median 29) years. The most common complaint was pain, including 4 cases with pathological fracture and 5 with history of previous trauma. The tumor size ranged from 3.4 to 13.5 (median 5.6) cm. The lesion involved the femur (n=4), humerus (n=5) and iliac bone (n=5). Radiologic diagnoses included SBC, aneurysmal bone cyst, and giant cell tumor of the bone or its combination with aneurysmal bone cyst-like region and fibrous dysplasia. Histologically, the cyst walls of the lesions were composed of fibrous tissue, fibrin-like collagen deposits, bone-like matrix and occasional woven bone. The lesional cells were spindled to ovoid, with scattered osteoclast-like giant cells, foamy histiocytes, hemosiderin deposits and cholesterol clefts. In 6 cases there were nodular fasciitis-like areas. Immunohistochemically, the spindled to ovoid cells were positive for SMA, EMA and SATB2 in varying degrees. FISH detection was performed in all 14 cases and EWSR1/FUS rearrangement were found in 9 cases. One case of FUS::NFATC2 fusion was detected by next-generation sequencing. Nine cases of SBC with the rearrangement were more cellular, and there were more mitotic figures in the recurrent FUS::NFATC2 fusion tumor. Clinical follow-up was obtained in all 14 cases with the time ranging from 5 to 105 (mean 46) months. Amongst them, the tumor with FUS::NFATC2 rearrangement had local recurrence twice after the first local excision, but had no more recurrence or metastasis 34 months after the subsequent segmental resection. The other 13 cases had no recurrence. Conclusions: EWSR1 or FUS rearrangement is most commonly identified in SBC, suggesting that SBC might be a neoplastic disease. In cases where the radiologic appearance and histomorphology are difficult to differentiate from aneurysmal bone cyst, FISH detection can aid in the definitive diagnosis.

Unravelling the USP6 gene: an update

Ubiquitin-specific protease 6 (USP6) rearrangements have been identified in aneurysmal bone cyst, nodular fasciitis, myositis ossificans, fibro-osseous pseudotumour of digits and cellular fibroma of tendon sheath. These entities show clinical as well as histological overlap, suggesting they are all clonal neoplastic belonging to the same biological spectrum and referred to as 'USP6-associated neoplasms'. They all show a characteristic gene fusion formed by juxtaposition of the USP6 coding sequences to the promoter regions of several partner genes, leading to USP6 transcriptional upregulation.

Aneurysmal Bone Cyst of the Orbit With USP6 Gene Rearrangement

PURPOSE

Aneurysmal bone cyst (ABC) of the orbit is a very rare tumor, occurring mostly in the pediatric population, and can result in sight threatening complications and disfigurement. This review discusses previously reported cases with a focus on evolving treatment options and molecular genetics.

METHODS

We report the youngest case of an orbital ABC with a confirmed gene fusion: a 17-month-old girl, with confirmed FGFR-UPS6 (Fibroblast Growth Factor Receptor 1-ubiquitin specific peptidase 6/tre-2). A literature search for relevant publications on the topic was performed via Medline and PubMed, with the appropriate data extracted.

RESULTS

Thirty-two cases of orbital aneurysmal bone cyst were identified in the literature. Presentations are varied and can include pain, proptosis, decreased vision, and extraocular motility disturbance. Typical imaging and histopathology findings are discussed, in particular the usefulness of identifying USP6 gene arrangements. Treatment modalities are reviewed including surgery, embolization, and receptor activator of nuclear factor kappa-B ligand (RANKL) inhibitors. Recurrences can occur, usually within 2 years.

CONCLUSIONS

Orbital ABC is a neoplasm that presents unique diagnostic and treatment challenges. Gene rearrangements can confirm primary ABC and rule out other underlying pathology. Disfigurement and sight threatening complications can occur due to both the disease process and with treatment. Outcomes may be improved with the use of systemic therapy.

Expanding the Spectrum of EWSR1-NFATC2-rearranged Benign Tumors: A Common Genomic Abnormality in Vascular Malformation/Hemangioma and Simple Bone Cyst

A simple bone cyst (SBC) is a cystic bone lesion predominantly affecting young males. The cyst is lined by a fibrous membrane and filled with serosanguinous fluid. EWSR1/FUS-NFATC2 rearrangements were recently identified in SBC. We here report exactly the same rearrangement in 3 lesions diagnosed as vascular malformations of 2 elderly patients. In total, through Archer FusionPlex, fluorescence in situ hybridization and/or reverse transcriptase-polymerase chain reaction the EWSR1-NFATC2 rearrangement was identified in 6 of 9 SBC, 3 of 12 benign vascular tumors, and none of 5 aneurysmal bone cyst lacking USP6 fusion. Using fluorescence in situ hybridization, it was apparent that amplification of the fusion, as seen in EWSR1-NFATC2 round cell sarcomas, was absent, and that in the vascular tumors the fusion was present both in the lining cells as well as in the surrounding spindle cells. Of note, not all of the spaces in the vascular malformations were lined by endothelial cells. Aggrecan was positive in all cases but was not specific. NKX2-2 and NKX3-1 staining were negative in all cases. Thus, even though the overlap between the 2 entities is limited to the presence of few thick-walled cysts lacking endothelial lining in the benign vascular malformations, the spectrum of benign tumors containing NFATC2 fusions should be expanded and contains not only SBC in the young, but also vascular malformation/hemangioma in elderly patients.

Validation of Fluorescence in situ Hybridization Testing of USP6 Gene Rearrangement for Diagnosis of Primary Aneurysmal Bone Cyst

GOALS

Ubiquitin specific protease 6 (USP6) gene rearrangement has been reported in approximately 70%-75% of aneurysmal bone cyst cases. We hypothesize that fluorescence in situ hybridization (FISH) testing of this marker will be useful in the pathological differentiation of primary aneurysmal bone cyst (ABC), secondary ABC, giant cell tumor of bone (GCT), and telangiectatic osteosarcoma (TOS) which are morphologically similar. This study aims to evaluate the efficacy of this test and validate it for diagnostic use.

PROCEDURES

FISH was performed in primary ABC, secondary ABC, GCT and TOS using dual color USP6 gene break apart probes. The sensitivity, specificity, positive predictive value, and negative predictive values were calculated.

RESULTS

Primary ABC demonstrates USP6 rearrangement. All secondary ABC, GCT and TOS were negative. The test sensitivity and specificity in primary ABC were 53% (9/17) and 100% (18/18), respectively. The positive predictive value and negative predictive value were 100% (9/9) and 69% (18/26), respectively.

CONCLUSION

The USP6 gene break apart detected by FISH is validated as a novel diagnostic tool for primary ABC in our laboratory. This test could be used to study the predictive value of USP6 targeted therapy for primary ABC in the near future.

Aneurysmal Bone Cyst of the Maxillary Sinus with USP6 Rearrangement: Case Report of a Rare Entity and Review of the Literature

Aneurysmal bone cysts (ABCs) are benign lesions which most frequently occur in the long bones of pediatric patients. Long thought to be reactive, recent molecular advances have demonstrated that the majority of primary ABCs harbor rearrangements of the USP6 gene, confirming their neoplastic nature. Secondary ABCs arising from other lesions do not demonstrate this recurrent genetic anomaly. ABCs rarely occur in the craniofacial bones, and sinonasal ABCs are exceedingly rare. We report a case of a primary ABC arising the maxillary sinus of a 14-year-old female, which was found to harbor USP6 rearrangement. We describe the clinical, radiologic, and pathologic features of this case, and review the current literature on craniofacial ABCs. Careful histologic evaluation and genetic studies are warranted in order to confirm the rare occurrence of a primary sinonasal ABC.

Aneurysmal bone cystic lesions: value of genomic studies

Aneurysmal bone cystic (ABC) lesions can be primary or secondary (to a trauma or a pre-existing benign or malignant tumour). Specific translocations of the USP6 gene are reported in about 70% of primary but never in secondary ABC lesions. We report two cases of ABC lesions in which imbalanced genomic aberrations were detected at initial presentation and showed complex clonal evolution. These demonstrative observations strengthen the guidelines regarding the diagnostic approach when an ABC is suggested by imaging. Biopsy is mandatory including genomic analysis. When a primary ABC is not clearly proven by the initial biopsy, an extensive curettage should be performed, with pathological examination of all removed tissue in order to exclude a secondary ABC. It also illustrates the added value of genomic analyses in the setting of an ABC lesion: complex clonal aberrations argues for a lesion secondary to a malignant proliferation whereas USP6 rearrangement allows the diagnosis of primary ABC.

Receptor-Activator of Nuclear KappaB Ligand Expression as a New Therapeutic Target in Primary Bone Tumors

The receptor-activator of nuclear kappaB ligand (RANKL) signaling pathway plays an important role in the regulation of bone growth and mediates the formation and activation of osteoclasts. Osteoclasts are involved in significant bone resorption and destruction. Denosumab is a fully human monoclonal antibody against RANKL that specifically inhibits osteoclast differentiation and bone resorption. It has been approved for use for multiple myeloma and bone metastases, as well as for giant cell tumor of bone. However, there is no previous report quantitatively, comparing RANKL expression in histologically varied bone tumors. Therefore, we analyzed the mRNA level of various bone tumors and investigated the possibility of these tumors as a new therapeutic target for denosumab. We examined RANKL mRNA expression in 135 clinical specimens of primary and metastatic bone tumors using real-time PCR. The relative quantification of mRNA expression levels was performed via normalization with RPMI8226, a human multiple myeloma cell line that is recognized to express RANKL. Of 135 cases, 64 were also evaluated for RANKL expression by using immunohistochemistry. Among all of the tumors investigated, RANKL expression and the RANKL/osteoprotegerin ratio were highest in giant cell tumor of bone. High RANKL mRNA expression was observed in cases of aneurysmal bone cyst, fibrous dysplasia, osteosarcoma, chondrosarcoma, and enchondroma, as compared to cases of multiple myeloma and bone lesions from metastatic carcinoma. RANKL-positive stromal cells were detected in six cases: five cases of GCTB and one case of fibrous dysplasia. The current study findings indicate that some primary bone tumors present new therapeutic targets for denosumab, particularly those tumors expressing RANKL and those involving bone resorption by osteoclasts.

Frequency of USP6 rearrangements in myositis ossificans, brown tumor, and cherubism: molecular cytogenetic evidence that a subset of "myositis ossificans-like lesions" are the early phases in the formation of soft-tissue aneurysmal bone cyst

OBJECTIVE

USP6 rearrangements with several partner genes have been identified recently in primary but not in secondary aneurysmal bone cysts (ABCs). Several lesions show histologic features that may overlap with ABC, including myositis ossificans (MO), brown tumor, and cherubism. The objective of this study was to assess whether these lesions harbored USP6 rearrangements.

MATERIALS AND METHODS

Twelve patients with classic radiologic and histologic features of MO, 6 with brown tumors, and 5 with cherubism diagnosed at our institution were studied for the presence of USP6 rearrangements using fluorescence in situ hybridization with probes flanking the USP6 locus on chromosome 17p13. In addition, conventional cytogenetic analysis was performed in 2 patients with cherubism.

RESULTS

USP6 rearrangements were identified in 2 patients with radiologic and histologic features consistent with MO. None of the patients with brown tumor or cherubism demonstrated USP6 rearrangements. Cytogenetic analysis of the cherubism patients demonstrated normal karyotypes.

CONCLUSION

These findings indicate that a subset of cases with apparent classic histologic and imaging features of MO are rather better classified as being soft-tissue ABC with clonal USP6 rearrangements. In contrast, no USP6 rearrangements were found in patients with cherubism or brown tumor, supporting the prevailing view that these lesions are distinct biologic entities.

Novel karyotypes in giant cell-rich lesions of bone

Giant cell-rich lesions of bone, including giant cell tumor of bone, giant cell reparative granuloma (GCRG), and aneurysmal bone cyst (ABC), may have overlapping clinical, radiologic, and histopathologic features. In fact, GCRG and solid ABC are currently differentiated solely based on skeletal location. Prior cytogenetic studies have reported that telomeric associations are present in the majority of giant cell tumors of bone, whereas translocations involving 16q22 and/or 17p13 are characteristic of ABCs. There is only one previously published karyotype of a GCRG, which revealed a reciprocal translocation, t(X;4)(q22;q31.3). We report 3 cases of giant cell-rich bone lesions with novel karyotypes: one lesion located in the first metacarpal, a typical location for GCRG, was histologically consistent with a giant cell tumor and showed the following karyotype [46,XX,inv(2)(p13q21),t(inv2;11)(q21;q13)]; the second lesion, also a giant cell tumor of bone, in the sacrum showed the following karyotype [46,XX,r(9)(p24q34)[cp7]/46,idem,?r(16)(p13.3q24)[cp10]/46,XX]. The third lesion, a hard palate mass, had the histopathologic features of a GCRG and a karyotype showing a reciprocal translocation, 46,XY,t(2;10)(q23;q24). These findings suggest that at least a subset of GCRGs may be neoplastic and that these lesions differ cytogenetically from classic giant cell tumors of bone or solid ABC, although the latter entity is otherwise indistinguishable from reparative granuloma. Further cytogenetic characterization of giant cell-rich bone lesions may improve the utility of karyotyping as a tool in their differential diagnosis and may shed light on the pathogenetic relationship between these lesions.

Soft-tissue aneurysmal bone cyst: report of a case with t(5;17)(q33;p13)

We describe a primary aneurysmal bone cyst (ABC) of the soft tissue of the distal thigh in a 10-year-old girl. Radiographs showed an oblong density in the soft tissue that was consistent with hemorrhage or calcification; the underlying bone was unremarkable. Pathologic findings were consistent with myositis ossificans on gross examination, but numerous hemorrhagic cysts were present in the lesion. Histopathologic findings showed features of an ABC. Cytogenetic analysis of the tumor revealed 46,XX,t(5;17)(q33;p13); 17p13 breakpoints have been reported in intraosseous ABC. Thirteen months after diagnosis, the patient had excellent function and no radiologic evidence of recurrent disease. Soft-tissue ABC is a rare, benign lesion that can have a similar radiologic appearance to myositis ossificans but has a histologic appearance identical to that of its intraosseus counterpart.

Aneurysmal bone cyst variant translocations upregulate USP6 transcription by promoter swapping with the ZNF9, COL1A1, TRAP150, and OMD genes

Aneurysmal bone cysts (ABC) are locally aggressive bone tumors that often feature chromosome 17p13 rearrangements. One of the ABC 17p13 rearrangements--t(16;17)(q22;p13)--was recently shown to create a CDH11-USP6 fusion in which the USP6/TRE17 oncogene is overexpressed through juxtaposition with the CDH11 promoter. Herein, we characterize four different ABC translocations involving 17p13, and we show that each is associated with a novel USP6 fusion oncogene. Specifically, we demonstrate that t(1;17), t(3;17), t(9;17), and t(17;17) result in USP6 fusions with TRAP150 (thyroid receptor-associated protein 150), ZNF9 (ZiNc Finger 9), Osteomodulin, and COL1A1 (Collagen 1A1), respectively. The oncogenic mechanism in these fusion genes is akin to CDH11-USP6, with the USP6 coding sequences juxtaposed to the promoter regions in each of the four novel translocation partners. The novel fusion partners appear well suited to drive USP6 transcription in the bone/mesenchymal context: osteomodulin is expressed strongly in osteoblastic lineages, and the COL1A1 promoter has an oncogenic role in the mesenchymal cancer dermatofibrosarcoma protuberans. In summary, these studies show that USP6 oncogenic activation results from heterogeneous genomic mechanisms involving USP6 transcriptional upregulation by juxtaposition with ectopic promoters.

USP6 and CDH11 oncogenes identify the neoplastic cell in primary aneurysmal bone cysts and are absent in so-called secondary aneurysmal bone cysts

Aneurysmal bone cyst (ABC) is a locally recurrent bone lesion that has been regarded as a reactive process. Recently, a neoplastic basis in primary ABC was evidenced by demonstration of clonal chromosome band 17p13 translocations that place the USP6 (TRE2 or TRE17) oncogene under the regulatory influence of the highly active CDH11 promoter. Herein, we report CDH11 and/or USP6 rearrangements in 36 of 52 primary ABCs (69%), of which 10 had CDH11-USP6 fusion, 23 had variant USP6 rearrangements without CDH11 rearrangement, and three had variant CDH11 rearrangements without USP6 rearrangement. USP6 and CDH11 rearrangements were restricted to spindle cells in the ABC and were not found in multinucleated giant cells, inflammatory cells, endothelial cells, or osteoblasts. CDH11 and USP6 rearrangements did not correlate with recurrence-free survival, or with other clinicopathological features. CDH11 and USP6 rearrangements were not found in any of 17 secondary ABC associated with giant cell tumor, chondroblastoma, osteoblastoma, and fibrous dysplasia. These findings demonstrate that primary ABC are mesenchymal neoplasms exhibiting USP6 and/or CDH11 oncogenic rearrangements. By contrast, secondary ABC lack CDH11 and USP6 rearrangements, and although morphological mimics of primary ABC, appear to represent a non-specific morphological pattern of a diverse group of non-ABC neoplasms.

Aneurysmal bone cyst: a hereditary disease?

Recent genetic and immunohistochemical studies propose that the primary aneurysmal bone cyst is a tumour and not a reactive tumour-simulating lesion. Based on a familial case of aneurysmal bone cyst the authors contacted 135 patients with this disease. Sixty-eight females and 67 males (median age 14 years; range 2-73 years) were asked if other family members had bone lesions. One hundred and seven patients (79%) denied having other family members with lesions, 23 patients (17%) did not answer, and five patients (4%) gave evidence of other bone lesions in the family. These data indicate that a predisposing genetic defect could be part of a multifactorial pathogenesis in the development of some aneurysmal bone cysts.

Cytogenetic and molecular cytogenetic findings in 43 aneurysmal bone cysts: aberrations of 17p mapped to 17p13.2 by fluorescence in situ hybridization

Aneurysmal bone cyst is a benign, cystic lesion of bone composed of blood-filled spaces separated by fibrous septa. Relatively few cases of aneurysmal bone cyst have been cytogenetically characterized, yet abnormalities of the short arm of chromosome 17 appear to be recurrent. In this study, conventional cytogenetic analysis of 43 aneurysmal bone cyst specimens from 38 patients over a 12-year period revealed clonal chromosomal abnormalities in 12 specimens. Karyotypic anomalies of 17p, including a complex translocation and inversion, were identified in eight of these 12 specimens. In an effort to further define the aberrant 17p breakpoint, fluorescence in situ hybridization (FISH) analyses were performed using a series of probe combinations spanning a 5.1 Mb region between the TP53 (17p13.1) and Miller-Dieker lissencephaly syndrome (17p13.3) gene loci. These studies revealed the critical breakpoint locus at 17p13.2, flanked proximally by an RP11-46I8, RP11-333E1, and RP11-457I18 bacterial artificial chromosome (BAC) probe cocktail and distally by an RP11-198F11 and RP11-115H24 BAC and RP5-1050D4 P1 artificial chromosome (PAC) probe cocktail. Overall, abnormalities of the 17p13.2 locus were identified by metaphase and/or interphase cell FISH analysis in 22 of 35 (63%) aneurysmal bone cyst specimens examined including 26 karyotypically normal specimens. These cytogenetic and molecular cytogenetic findings expand our knowledge of chromosomal alterations in aneurysmal bone cyst, further localize the critically involved 17p breakpoint, and provide an alternative approach (ie FISH) for detecting 17p abnormalities in nondividing cells of aneurysmal bone cysts. The latter could potentially be utilized as an adjunct in diagnostically challenging cases.

USP6 (Tre2) fusion oncogenes in aneurysmal bone cyst

Aneurysmal bone cyst (ABC) is a locally aggressive osseous lesion that typically occurs during the first two decades of life. ABC was regarded historically as a nonneoplastic process, but recent cytogenetic data have shown clonal rearrangements of chromosomal bands 16q22 and 17p13, indicating a neoplastic basis in at least some ABCs. Herein we show that a recurring ABC chromosomal translocation t(16;17)(q22;p13) creates a fusion gene in which the osteoblast cadherin 11 gene (CDH11) promoter region on 16q22 is juxtaposed to the entire ubiquitin-specific protease USP6 (Tre2) coding sequence on 17p13. CDH11-USP6 fusion transcripts were demonstrated only in ABC with t(16;17) but other ABCs had CDH11 or USP6 rearrangements resulting from alternate cytogenetic mechanisms. CDH11 is expressed strongly in bone, and our findings implicate a novel oncogenic mechanism in which deregulated USP6 transcription results from juxtaposition to the highly active CDH11 promoter.

Metachronous and multiple aneurysmal bone cysts: a rare variant of primary aneurysmal bone cysts

In 1942, Jaffe and Lichtenstein introduced the term aneurysmal bone cyst (ABC). Primary ABC is characterized by the presence of spongy or multi-cameral cystic tissue filled with blood. The process is benign, but it is locally destructive and has a high propensity for recurrence. In this paper, we present the third case of multiple metachronous primary ABCs as a rare variant of ABC. We describe the 10-year history of a 12-year-old boy with metachronous multiple primary ABCs at five different sites (right proximal humerus, right ulna, bilateral distal radius and right lateral clavicle). Furthermore, our patient suffered from vascular malformations, such as aortic isthmus stenosis, hypoplastic thoraco-abdominal aorta and bilateral renal artery stenosis. To date, in contrast to solitary ABC, the multiple lesions have been found more frequently in male individuals. Using interphase cytogenetics, we analyzed three of five of the patient's ABCs and one of these was also analyzed by GTG-banding. No chromosomal abnormalities were found. Significantly, we excluded the missense mutation of codon 201 in guanine nucleotide-binding protein 1 gene consistently found in McCune-Albright syndrome (MAS) and in non-MAS cases of polyostotic fibrous dysplasia of bone with or without secondary ABC.

[Comparative DNA cytometric investigations on aneurysmal bone cysts and giant cell tumors]

Giant cell-rich bone lesions consist of tumor-like lesions and true neoplastic giant cell tumors. In this study it was investigated whether DNA cytometry may contribute to the differential diagnosis between aneurysmal bone cysts and giant cell tumors. Statistically significant differences in the frequency of tetraploid stemlines were detected. Nevertheless, the knowledge of age, localization and radiological signs in addition to morphological findings are essential to distinguish between these lesions.

Soft tissue aneurysmal bone cyst: a clinicopathologic study of five cases

We describe five primary soft tissue tumors that had histologic features identical to intraosseous aneurysmal bone cyst. The tumors occurred in three females and two males, who ranged in age from 8 to 37 years (median 28 years). They arose in the deep soft tissue of the upper extremities, thigh, and groin region and typically presented as a rapidly growing mass; no involvement of the adjacent bones was identified. The tumors ranged in size from 2.5 to 9 cm (median 4 cm). Grossly, they were surrounded by a thin rim of bone and on sectioning had hemorrhagic cystic spaces delineated by fibrous septa. Histologically, the cystic spaces were filled with blood and the fibrous septa were composed of fibroblasts, osteoclast-type giant cells, and woven bone. Cytogenetic analysis of one tumor showed 46,XY,t(17;17)(p13;q12), a result similar to that which has been reported for intraosseous aneurysmal bone cyst. The differential diagnosis includes a variety of bone-forming and giant cell-containing tumors, the most important being extraskeletal osteosarcoma. Follow-up showed that four patients are free of disease 16 months to 10 years after surgery; one tumor regrew after incomplete initial excision, but the patient has been free of disease 16 months after a second operation. Soft tissue aneurysmal bone cyst is an uncommon benign tumor that can be treated by simple excision, and it should be distinguished from a variety of other reactive and neoplastic processes.

Aneurysmal bone cyst of the nose with 17p13 involvement

We report on a 6-year-old girl with a polypoid mass, filling up the entire right nasal cavity as shown on a magnetic resonance imaging scan. Histologically, the tumor had the characteristics of an aneurysmal bone cyst, which is extremely rare in this location. Cytogenetic analysis disclosed a single (6:17)(p21;p13) translocation, confirming a specific genetic involvement in the development of aneurysmal bone cysts. Fluorescent in situ hybridization analysis mapped the putative gene between the p53 (17p13.1) and the Mieller-Dieker gene (17p13.3) loci.

Expression of insulin-like growth factor-I (IGF-I) in aneurysmal bone cyst

The effects of insulin-like growth factor-I on bone tissue and its role in bone development have been extensively investigated, but there is little information on its role in the pathogenesis of aneurysmal bone cyst. Therefore, using the techniques of immunohistochemistry and in situ hybridization, the authors studied the expression of insulin-like growth factor-I in 19 specimens of aneurysmal bone cyst. Insulin-like growth factor-I or specific mRNA sequences encoding for insulin-like growth factor-I were detectable in all specimens tested and were mainly localized in multinucleate giant cells. In contrast, only insignificant levels of insulin-like growth factor-I expression were detectable in normal human bone tissue. Taken together with the previously reported role of insulin-like growth factor-I in the pathogenesis of giant cell tumor, the findings of this study suggest that insulin-like growth factor-I may play a role in the pathogenesis of aneurysmal bone cyst.

Aneurysmal bone cyst with chromosomal changes involving 7q and 16p

An aneurysmal bone cyst was submitted to cytogenetic analysis. The modal chromosome number was 46. The composite karyotype was 40 approximately 48,XY,-Y[4],-6[3],del(7)(q32)[3],-9[3],+12[2],+13[2], inv(16)(p13.1q24)[4],-17[3],-19[4],-20[3][cp13]. The clonal structural changes detected were del(7)(q32) and inv(16)(p13.1q24). The breakpoints involved affected areas to which important genes for cell cycle regulation have been mapped. There is only one report in the literature of three aneurysmal bone cysts presenting clonal karyotypic alterations. The cytogenetic study of the aneurysmal bone cyst reported here showed different results when compared to those previously described in the literature.

Translocation (16;17)(q22;p13) is a recurrent anomaly of aneurysmal bone cysts

Recently, Panoutsakopoulos et al. (1999) reported 2 cases of aneurysmal bone cysts with a recurrent (16;17)(q22;p13) translocation. We present here two additional cases harboring the same translocation as well as additional chromosomal changes.

Cytogenetic-morphologic correlations in aneurysmal bone cyst, giant cell tumor of bone and combined lesions. A report from the CHAMP study group

Aneurysmal bone cyst and giant cell tumor of bone are relatively rare bone tumors that sometimes coexist. We examined the karyotypes of 3 aneurysmal bone cysts, 12 giant cell tumors, and 3 combined lesions. All aneurysmal bone cysts showed involvement of chromosome segments 17p11-13 and/or 16q22. In addition, in 1 of the 3 giant cell tumors with secondary aneurysmal bone cyst, both chromosome bands were rearranged as well, albeit not in a balanced translocation. Seven out of 12 giant cell tumors were characterized by telomeric associations. One giant cell tumor showed a dup(16)(q13q22), suggesting the presence of a (minor) secondary aneurysmal bone cyst component, despite the absence of histological proof. Our results, combined with literature data further substantiate that segments 16q22 and 17p11-13 are nonrandomly involved in at least some aneurysmal bone cysts, irrespective of subtype (primary, secondary, intra/extraosseous, solid or classic). These findings strongly suggest that some aneurysmal bone cysts are true neoplasms. In addition, telomeric associations are the most frequent chromosomal aberrations in giant cell tumor of bone, the significance of which remains elusive. In combined giant cell tumor/aneurysmal bone cyst each component seems to retain its own karyotypic abnormality.

Aneurysmal bone cyst of the spine with familial incidence

STUDY DESIGN

A report of two cases of aneurysmal bone cysts of the spine occurring in a father and daughter.

OBJECTIVE

To present an unusual finding of familial incidence of aneurysmal bone cyst and review the literature.

SUMMARY OF BACKGROUND DATA

Aneurysmal bone cysts are benign, expanding, locally aggressive lesions. Up to 20% of cases involve the spine. The cause of primary aneurysmal bone cysts remains unclear. There have been three previous reports of a familial incidence supporting the importance of a hereditary component in the cause of aneurysmal bone cysts.

METHODS

A 36-year-old man and a 7-year-old girl were diagnosed with aneurysmal bone cyst involving the spine by clinical manifestations, radiographic features, and histologic evaluation.

RESULTS

The father remains recurrence- and symptom-free 6 years after primary resection. Five months after surgery, the daughter was found to have recurrent disease by magnetic resonance imaging and underwent a second procedure within 1 year of the primary resection.

CONCLUSION

The occurrence of a primary aneurysmal bone cyst in two family members, occurring at adjacent vertebral levels, is suggestive of a hereditary component to the formation of primary aneurysmal bone cyst.

Telomerase activity in benign bone tumors and tumor-like lesions

To assess the role and status of telomerase activity in benign bone tumors and tumor-like lesions, we performed telomerase assays in four giant cell tumors of bone, four fibrous dysplasias, three osteochondromas, three aneurysmal bone cysts, two osteoblastomas, one juvenile bone cyst and one myositis ossificans. A very sensitive non-radioactive TRAP assay was applied. Low level activity was detected in 7 of 18 tumor samples (38.9%), and high level activity was not detected in any of the cases. Telomerase activity was observed in all patients with osteochondromas, in two of the three aneurysmal bone cysts, in one of the four giant cell tumors of bone and in one of the four fibrous dysplasias, but not in osteoblastomas, juvenile bone cyst and myositis ossificans. Although the origin of this enzyme is still unclear, it might play a role in precancerous immortalization of benign bone tumors. Other possible reasons explaining the occurrence of telomerase activity, such as migrating lymphocytes or contamination of immortalized non-tumor cells, should not be ruled out. Telomerase activity, however, does exist in those samples having no malignant phenotype, for which reason telomerase assays are not always useful for the clinical and diagnostic approach in benign bone tumors. Determination of the telomerase status in benign lesions may contribute to a better understanding of the regulation mechanism of telomerase activity during progression of bone tumors.

Recurrent t(16;17)(q22;p13) in aneurysmal bone cysts

Aneurysmal bone cyst (ABC) is a benign bone lesion for which no previous cytogenetic data exist. We describe the finding of clonal chromosome aberrations in three tumors; two had a t(16;17)(q22;p13) as the sole anomaly, and the third had a del(16)(q22) as the only change. These findings show that somatic mutations contribute to the development of ABC and furthermore indicate that bands 16q22 and 17p13 may harbor genes of importance in this process.

A case of aneurysmal bone cyst in father and son

The authors report a familial case of primary aneurysmal bone cyst in father and son, affecting both at the same location at nearly the same age. This fact again raises the speculation of a genetic link as another factor in the pathogenesis of aneurysmal bone cyst.

Expression of regulatory apoptotic proteins in peripheral giant cell granulomas and lesions containing osteoclast-like giant cells

Peripheral giant cell granuloma consists of mononuclear cells and osteoclast-like giant cells. The proliferative ability of peripheral giant cell granuloma is restricted to the mononuclear cell compartment, whereas multinucleated giant cells lack mitotic activity. Although the proliferative compartment of peripheral giant cell granuloma has been investigated in detail, the expression and distribution of proteins regulating apoptosis is unknown. The present study demonstrates strong expression of bak and bax in the majority of giant cells. In contrast, giant cells show only weak positivity for bcl-2 and moderate positivity for bcl-x. Mononuclear cells were negative to weakly positive for bcl-x. Only scattered mononuclear cells were positive for bak, bax and bcl-2. The frequency of apoptotic nuclei detected by TUNEL-staining compared to regular nuclei was 18 times higher in giant cells than in mononuclear cells. In summary, our findings support the presumption that giant cells of bone and soft tissue tumors are reactive cell forms and not of neoplastic origin.

[Cell proliferation in bone tumors. Immunohistologic study of Ki-67 protein expression]

Bone tumors represent a group of tumors of various dignity. In spite of this single tumor entities may display strong morphological resemblance to each other which can in turn result in profound difficulties in differential diagnosis. The biological behaviour of a tumor is mainly determined by its rate of proliferation. In this study the rate of proliferation of 64 bone tumors (30 high-grade central osteosarcomas, 6 low-grade osteosarcomas, 8 giant cell tumors, 8 aneurysmatic bone cysts, 5 osteoidosteomas/osteoblastomas, 7 fibrous dysplasias and 5 cases of a myositis ossificans) were analysed. Immunohistochemistry was performed on paraffin-embedded tissue sections using the MIB-1 monoclonal antibody. MIB-1 recognizes the proliferation-associated Ki-67 protein which is expressed during the active phases of the cell cycle but cannot be detected in senescent cells. Among high-grade central osteosarcomas a significantly higher rate of proliferation (average value 30%) was found in comparison with low-grade osteosarcomas and other benign intraosseous bone tumors. This approach proved to be very useful in the distinction between high-grade and low-grade osteosarcomas as well as bone-forming intraosseous tumors. However distinguishing low-grade osteosarcomas from benign bone tumors by determining only the rate of proliferation was not possible, although interestingly, the proliferative rate of myositis ossificans, a purely reactive lesion, was in the range of the values determined for high-grade osteosarcoma.

[DNA cytometry of solitary and aneurysmal bone cysts and low malignancy and high malignancy central osteosarcomas. Current significance within the scope of morphologic diagnosis of intraosseous cystic and osteoblastic lesions]

DNA cytometric investigations of intraosseous cystic lesions and osteoblastic tumors may be helpful in morphological diagnosis. The detection of a DNA-aneuploid stemline supports the diagnosis of a high-grade malignant bone neoplasm, even in small biopsies. Solitary and aneurysmal bone cysts have DNA-diploid cell populations. Low-grade central osteosarcomas may show single-cell aneuploidies of varying extent as well as a DNA-diploid stemline. Their presence may be a sign of genetic instability within the population of neoplastic cells before a DNA-aneuploid stemline is established and should prompt careful postoperative observation.

Focal dermal hypoplasia (Goltz syndrome) with vertebral solid aneurysmal bone cyst variant. A case report

Focal dermal hypoplasia or Goltz syndrome is a rare clinical entity, usually presenting in early childhood as a mix of ectodermal and mesodermal anomalies. Previously reported cases have included skeletal lesions of the long bones, metacarpals, metatarsals and pelvis. We present a case with a vertebral lesion causing neurologic deficit. A discussion of the history of the syndrome is included as well as detailed histologic description.