Metastatic potential of an aneurysmal bone cyst

Aneurysmal bone cyst: a review

Aneurysmal bone cyst (ABC) is a benign locally destructive bone neoplasm composed of multi-loculated blood-filled cystic spaces. The most common sites of involvement are the meta-diaphysis of the long bones and posterior elements of the vertebrae. Secondary, ABC-like changes can complicate a variety of other benign and malignant primary bone neoplasms, including giant cell tumor, fibrous dysplasia, and osteosarcoma. About two-third of primary ABCs have a rearrangement of the USP6 gene, which is not present in the ABC-like changes that occur secondary to other primary bone tumors (i.e., secondary ABC). Primary ABC of bone carries a variable but generally high rate of local recurrence. This paper provides an overview of the pathophysiology, clinical presentation, radiographic and pathologic findings, treatment, and prognosis of ABC.

Uncommon Bone Injuries in Soccer Players

Soccer is the most common team sport in the world. A significant number of players are associated with a large number of injuries. Injuries occur in a variety of contexts regardless of the age or performance level of players. The vast majority of injuries involve soft tissues. Bone injuries are less common, but usually result in long-term exclusion from the game. Three different types of fractures related to soccer are classified as acute types, stress fractures and avulsion. This manuscript outlines the diagnostic procedures and treatments for stress fractures, avulsion fractures and bone cyst. The common feature of the described injuries includes frequent difficulties associated with the correct diagnosis and treatment direction. In therapeutic treatment, the doctor and the patient often have to choose between conservative treatment and surgical treatment, which in many cases is not simple. We suggest that in the event of injuries to soccer players, surgical treatment should be used, shortening the time to return to full sports activity. A very important element of the therapeutic process is proper rehabilitation, which should be individually tailored to the patient in order to optimize the treatment process. Some of the rehabilitation protocols should be permanently incorporated into the warm-up protocols for training. Such a procedure has a preventive effect.

Unusual split green-orange signals in USP6 fluorescence in situ hybridization in a malignant peripheral nerve sheath tumor with a novel NF1-SCIMP fusion: a potential diagnostic pitfall

Deletion of the neurofibromatosis 1 (NF1) gene is common, but NF1 rearrangement or fusion has rarely been reported in peripheral nerve sheath tumors. Here, we present a case of malignant peripheral nerve sheath tumor (MPNST) in a 36-year-old Chinese female. Histologically, the lesion was composed of spindle cells with moderate atypia, immature bone, and atypical cartilage elements. Fluorescence in situ hybridization (FISH) for USP6 revealed green-orange split signals, strongly suggesting the presence of USP6 rearrangement. Subsequent next-generation sequencing-based technology analyses revealed t(17,17) (p13.2, q11.2) intrachromosomal translocation resulting in a novel NF1-SCIMP fusion gene along with NF1 deletion. However, USP6 fusion was not identified. To the best of our knowledge, this is the first case with a confirmed NF1 gene fusion partner in a peripheral nerve sheath tumor. Notably, rearrangement of the SCIMP may cause a pitfall in the interpretation of USP6 FISH results.

Atypical nodular fasciitis with a novel PAFAH1B1-USP6 fusion in a 22-month-old boy

Nodular fasciitis (NF) rarely occurs in infants aged < 2 years although cranial fasciitis develops predominantly in this age group. Histologically, NF may present high cellularity and brisk mitoses, but atypical forms are generally absent. Here, we report a NF in a 22-month-old Chinese boy. Microscopically, the lesion was manifested as cellular variant of NF. Notably, atypical mitotic figures including multipolar form were identified. Immunohistochemically, the neoplastic cells showed strong positivity for smooth muscle actin. Fluorescence in situ hybridization analysis revealed an unbalanced rearrangement of USP6, along with the USP6 increased copies. Subsequent next-generation sequencing-based technology revealed a novel PAFAH1B1-USP6 fusion gene as well as unusual fusion point on USP6 (exon 9). To the best of our knowledge, this is the only reported case with overt atypical mitosis. This case is also the first published example of genetically confirmed infant NF. Additionally, PAFAH1B1-USP6 fusion has never been described in NF.

USP6-Associated Neoplasms: A Rapidly Expanding Family of Lesions

Nearly 20 years ago, the first description of a translocation involving chromosome 17 on which USP6 resides was described. Since then, not only the culprit gene but also many fusion partners, leading to transcriptional activation of USP6, have been detected. The first neoplasm known to harbor USP6 rearrangements was aneurysmal bone cyst. Since then, other entities like nodular fasciitis, myositis ossificans, fibro-osseous pseudotumor of digits, and a subgroup of fibromas of tendon sheath, probably representing tenosynovial nodular fasciitis, have been added to the list of USP6-rearranged lesions. Remarkably, all of them share clinical as well as morphological characteristics, and authors have suggested that these entities actually belong to the same spectrum. This review summarizes the current knowledge regarding USP6-rearranged lesions and further elaborates on how these neoplasms relate to one another. We propose to call these lesions UAN (Usp6-associated neoplasm).

[Updates to the WHO classification of bone tumours]

The fourth edition of the WHO Classification of Soft Tissue and Bone Tumours, published in 2013, extends the approach to describe genetics and pathology of these tumours in the context of epidemiological, clinical and imaging data, which was adopted in the third edition. Added are a few new entities, reclassifications and renamings. The most important point, also of clinical relevance and with consequences for treatment, is the introduction of a stratification of bone tumours based on their biological behaviour into three groups (benign, intermediate, malignant) in analogy to soft tissue tumours.

[Foot and ankle tumours : Part I: overview of incidence, diagnosis and staging of pedal tumours]

CLINICAL ISSUE

Foot and ankle tumours are rare. Part I of this paper provides a survey about tumour distribution regarding age and location of benign and malignant bone and soft tissue tumours.

STANDARD RADIOLOGICAL METHODS

All diagnostic radiological procedures are used for the diagnostic work-up of pedal tumours, in particular plain radiography, MRI, and ultrasonography.

METHODICAL INNOVATIONS

Dual-energy CT proves to be a valuable (differential) diagnostic tool in identifying urate dihydrate crystals.

PERFORMANCE

There are no reliable numbers available on accuracy of the aforementioned diagnostic procedures regarding tumour detection and identification. This is particularly true for soft tissue tumours which are small and well-defined, thus requiring histological clarification.

ACHIEVEMENTS

To evaluate pedal tumours correctly and reasonably, a full range of radiological diagnostics should be employed. Neither plain radiography alone nor a stand-alone MRI examination-depending on the tumour site-are sufficient to characterize such tumours including staging.

PRACTICAL RECOMMENDATIONS

Plain radiography remains the first-choice imaging modality. Ultrasonography is superior to reliably detect and identify ganglion cysts. MRI, however, continues to remain the upmost diagnostic modality of choice for evaluating foot and ankle tumours. CT possesses unchallanged diagnostic power to assess osseous changes. Bone scintigraphy (including SPECT-CT) and FDG-PET imaging are used when multifocal distribution or metastatic disease are suspected or to detect avidity of the pedal lesions, respectively.

Early Recurrence of a Solid Variant of Aneurysmal Bone Cyst in a Young Child After Resection: Technique and Literature Review and Two-year Follow-up After Corpectomy

Aneurysmal bone cysts (ABCs) are considered to be rare benign tumors that may affect long bones or the vertebral column. Their incidence varies and is reported to be 1.4% of all benign skeletal tumors. The solid-variant aneurysmal bone cyst (S-ABC) is even rarer and constitutes 3.5% to 7% of all vertebral ABCs. We report the case of an Enneking stage 3 S-ABC in a 5-year-old boy at C7 that showed rapid local recurrence after primary excision from posterior and dorsal stabilization requiring ventral corpectomy and posterior excision of the right lateral mass and right posterolateral fusion. Histologic examination disclosed an S-ABC. To our knowledge, this is the first case of S-ABC described in the literature that used both anterior and posterior approaches and complete corpectomy. Over a 2-year period, the patient showed no radiologic or clinical signs of local recurrence with excellent neurologic function. Solid-variant aneurysmal bone cysts are difficult to diagnose and treat, and careful clinical and radiologic assessment should be done to tailor an appropriate surgical plan to prevent recurrence and neurologic sequelae. To the best of our knowledge, there are to date no publications that studied the behavior of this subtype.

Radiotherapy for aneurysmal bone cysts : A rare indication

BACKGROUND

Aneurysmal bone cysts (ABC) are rapidly growing benign osseous lesions composed of blood-filled channels separated by fibrous septa. Since the value of external beam radiotherapy (EBRT) for ABC has not been well defined, the German Cooperative Group on Radiotherapy for Benign Diseases performed the national register study described herein.

PATIENTS AND METHODS

Five German institutions collected data regarding clinical features, treatment concepts, and outcome for patients with ABC who had been referred for local EBRT over the past 30 years.

RESULTS

Between 1990 and 2015, 10 patients with ABC were irradiated (5 female/5 male). Median age was 23 years (range 14-40 years). Involved sites were: spine (n = 3), sacrum/pelvis (n = 2), shoulder/scapula (n = 2), humerus (n = 1), femur (n = 1), and radius (n = 1). The median EBRT total and fractional doses were 28 Gy (range 5-40 Gy) and 2 Gy (range 1-2 Gy), respectively. Median follow-up was 65 months (range 12-358 months). Persistent pain relief was achieved for all patients. However, long-term follow-up response data were only available for 7/10 patients. All 7 patients exhibited a radiological response and experienced no recurrent disease activity or pain during follow-up. Acute and late radiogenic toxicities ≥ grade 3 and secondary malignancies were also not observed.

CONCLUSION

Primary or adjuvant EBRT seems to be an effective and safe treatment option for persistent or recurrent ABC. Fractionated doses below 30 Gy may be recommended.

Differential diagnostic value of "blue reticulated chondroid-like material" in aneurysmal bone cysts: a classic histopathologic analysis of 215 cases

OBJECTIVES

Our classic histopathologic study of aneurysmal bone cyst (ABC) revealed that "blue reticulated chondroid-like material" (BRC) is characteristic of ABC.

METHODS

The light microscopic findings were retrospectively analyzed in 215 cases of ABC, including 101 primary and 114 secondary cases. In addition, 22 cases of telangiectatic osteosarcoma (TOS) were drawn from the same source and used as a control.

RESULTS

We found the presence of typical BRC in 24 (23.8%) of 101 cases of primary ABC and in six (5.3%) of 114 cases of secondary ABC, with an overall incidence of 30 (14%). None of the cases of TOS showed BRC. BRC was significantly more common in primary ABC than in secondary ABC (P < .05) and in patients 19 years or younger than in those 20 years or older (P < .05).

CONCLUSIONS

BRC appears to be a unique histopathologic feature of ABC, making it valuable to differentiate benign ABC from TOS. Simple H&E stain can be economically performed anywhere.

USP6-induced neoplasms: the biologic spectrum of aneurysmal bone cyst and nodular fasciitis

USP6 (also known as TRE17) is a ubiquitin-specific protease that was identified as an oncogene in transfection experiments with Ewing sarcoma DNA 2 decades ago. Until recently, little was known about USP6 function and mechanisms of oncogenic activation. The identification of USP6 fusion genes in aneurysmal bone cyst (ABC) and, more recently, in nodular fasciitis led to a better understanding of the pathogenesis of these lesions. Furthermore, the detection of USP6 genomic rearrangements or USP6 fusion genes may be used as a diagnostic tool for these lesions. In this review, we discuss the clinicopathologic features, molecular pathology, and pathogenesis of ABC and nodular fasciitis. We also discuss the possible line of differentiation of ABC and its relationship to nodular fasciitis and other lesions.

Metachronous aneurysmal bone cyst in a 9-year-old boy: case report and review of the literature

Aneurysmal bone cyst (ABC) is a locally aggressive, benign bone tumor that commonly affects children. Metachronous ABCs are rare, and have been described only three times in the literature. Here we present a fourth case in a 9-year-old boy who presented with an ABC of the scapula; 2½ years later he presented with a tibial ABC. We also review the literature and discuss the pathological and clinical characteristics of this lesion.

Chondroblastoma with secondary aneurysmal bone cyst of the hamate: case report

Chondroblastoma of the carpals is rare, can mimic other benign bone tumors, and presents a diagnostic challenge. There have been few cases of benign tumors involving the hamate, with only one reported case of chondroblastoma, which was treated with complete hamate excision. We present a case of chondroblastoma with secondary aneurysmal bone cyst of the hamate treated with curettage, high-speed burring, phenol, and autogenous iliac crest bone grafting. At the time of the most recent radiographic follow-up, there was full graft incorporation, preserved hamate morphology, and no evidence of recurrence.

Soft tissue aneurysmal bone cyst in a 10-year-old girl

We report the case of a 10-year-old girl with a soft tissue aneurysmal bone cyst (STABC) located in the posterior aspect of the left shoulder. Conventional radiography revealed an oblong mass with a calcified rim. On the computed tomography scan, the lesion appeared to have a non-uniform intralesional density with an incomplete rim. Magnetic resonance imaging revealed a multi-cavity lesion with fluid-fluid levels. Following pathological examination, the lesion was diagnosed as a STABC. This may be only the twentieth reported case in the English literature of this extremely rare benign tumor occurring in soft tissue. Eight months after surgery the patient was assessed at our outpatient clinic and found to have excellent mobility of her left shoulder and no sign of recurrence.

Unknown partner for USP6 and unusual SS18 rearrangement detected by fluorescence in situ hybridization in a solid aneurysmal bone cyst

USP6 rearrangement is the most common genetic abnormality in primary aneurysmal bone cyst, and SS18 rearrangement has not been previously described in any type of tumor where synovial sarcoma was excluded from the differential diagnosis. We report a case of solid aneurysmal bone cyst in which fluorescence in situ hybridization (FISH) analysis indicated rearrangements of both USP6 and SS18, but histologic features were consistent with aneurysmal bone cyst throughout the lesion. Reverse-transcription polymerase chain reaction (RT-PCR) for the SS18-SSX1 and SS18-SSX2 translocations, identity testing, and SS18 FISH were performed on cytogenetic monolayer cultures and formalin-fixed paraffin-embedded (FFPE) tissue. Genomic microarray, FISH, and immunohistochemistry were performed on follow-up studies of the FFPE specimen. The karyotype was 45,X,add(X)(p11.2),add(4)(q13),add(8)(p21),-13,add(17)(p11.2),add(18)(q11.2) in all 20 cells analyzed from monolayer cultures. The karyotype showed no cytogenetically visible alterations of chromosomal regions harboring known partners for USP6. Metaphase FISH with a commercial SS18 break-apart probe showed translocation of the 5' portion of the SS18 probe to the short arm of the derivative X, as is observed in synovial sarcoma. RT-PCR showed no evidence of a SS18-SSX fusion, and immunohistochemistry was negative for TLE1, EMA, and cytokeratin AE1/3 expression. FISH on FFPE sections with a custom break-apart probe flanking USP6 showed evidence for a USP6 rearrangement throughout the tumor (25-50%). FISH on FFPE sections with a commercial SS18 break-apart FISH probe showed more variable results (0-50% split signals). There was no evidence of a SS18-USP6 fusion by FISH or RT-PCR. A molecular inversion probe array revealed a deletion encompassing the entire SS18 gene and its promoter, as well as portions of the region targeted by the commercial SS18 FISH probe. In conclusion, results obtained from commercially available FISH probes may occasionally yield misleading results. In this case, the SS18 rearrangement by FISH resulted from a complex rearrangement of 18q11.2 with a deletion of the SS18 gene. The translocation partner for USP6 remains unknown in this case.

TRE17/ubiquitin-specific protease 6 (USP6) oncogene translocated in aneurysmal bone cyst blocks osteoblastic maturation via an autocrine mechanism involving bone morphogenetic protein dysregulation

Aneurysmal bone cyst (ABC) is a pediatric osseous tumor characterized by extensive destruction of the surrounding bone. The molecular mechanisms underlying its pathogenesis are completely unknown. Recent work showed that translocation of the TRE17/USP6 locus occurs in over 60% of ABC cases resulting in TRE17 overexpression. Immature osteoblasts are presumed to be the cell type harboring translocation of TRE17 in at least a subset of ABCs. However, the effects of TRE17 overexpression on transformation and osteoblast function are unknown. TRE17 encodes a ubiquitin-specific protease (USP) and a TBC (TRE2-Bub2-Cdc16) domain that promotes activation of the Arf6 GTPase. Here we report that TRE17 potently inhibits the maturation of MC3T3 pre-osteoblasts in a USP-dependent and Arf6-independent manner. Notably, we find that TRE17 function is mediated through an autocrine mechanism. Transcriptome analysis of TRE17-expressing cells reveals dysregulation of several pathways with established roles in osteoblast maturation. In particular, signaling through the bone morphogenetic protein (BMP) pathway, a key regulator of osteogenesis, is profoundly altered. TRE17 simultaneously inhibits the expression of BMP-4 while augmenting the BMP antagonist, Gremlin-1. Osteoblastic maturation is restored in TRE17-expressing cells by the addition of exogenous BMP-4, thus establishing a functional role for BMP-4 during TRE17-induced transformation. Because bone homeostasis involves a precise balance between the activities of osteoblasts and osteoclasts, our studies raise the possibility that attenuated osteoblast maturation caused by TRE17 overexpression may contribute to the bone loss/destruction observed in ABC.

Emerging roles of deubiquitinases in cancer-associated pathways

Deubiquitinases (DUBs) are emerging as important regulators of many pathways germane to cancer. They may regulate the stability of key oncogenes, exemplified by USP28 stabilisation of c-Myc. Alternatively they can negatively regulate ubiquitin-dependent signalling cascades such as the NF-kappaB activation pathway. We review the current literature that associates DUBs with cancer and discuss their suitability as drug targets of the future.