Technical Feasibility and Outcome of Cryoablation of Aneurysmal Bone Cysts in Pediatric Patients.

PURPOSE: To evaluate the clinical and imaging outcome of aneurysmal bone cysts (ABCs) in children using percutaneous cryoablation as the sole treatment. MATERIALS AND METHODS: This retrospective study included 7 children with a mean age of 8.7 years (range, 3.0-11.9 years) who underwent at least 1 cryoablation for ABC. Cryoablation needles were placed and guided by computed tomography (CT). Imaging follow-up and clinical examination were performed by radiography 1 and 6 months after the procedure and magnetic resonance (MR) imaging was performed 3 and 12 months after the procedure. Additional cryoablation was performed in case of MR imaging-detected recurrence. Data were analyzed by anatomical location, measurement of lesion volume, numbers of intralesional cysts, grade of mineralization (5-point Likert scale), pain (0 [none] to 4 [severe]), and grade of fluid-fluid levels (FFLs; 4-point Likert scale). RESULTS: Fourteen cryoablations were performed. Patients showed volume reduction, with 1 showing a complete response and 6 showing partial response. Following treatment, there was a substantial reduction in lesion volume compared with baseline, leading to a mean volume decrease of 81.9% (range, 66.8%-100%). The grade of mineralization (3.2 [SD ± 1.2] after therapy vs 1.1 [SD ± 0.3] at baseline), grade of FFL (1.6 [SD ± 0.5] after therapy vs 3.4 [SD ± 1.1] at baseline), and pain (0.29 [SD ± 0.4] after therapy vs 1.86 [SD ± 0.7] at baseline) significantly improved after therapy (all P < .05). One severe adverse event occurred. CONCLUSIONS: Cryoablation is an effective treatment option for ABC in children. Further research is needed to compare it with other techniques.

Adjunct role of liquid absolute alcohol intralesional sclerotherapy during the surgical management of spinal primary aneurysmal bone cyst in a child: a technical case report.

BACKGROUND: Aneurysmal bone cyst is composed of variable -sized cystic blood-filled spaces separated by connective tissue septae. First-line surgical resection of spinal aneurysmal bone cyst in a child with limited total blood volume can lead to massive intraoperative bleeding, thus limiting extent of resection. Our Centre's has good experience of using absolute alcohol as an effective immediate devascularizing agent during vertebral hemangioma surgery in children. MATERIAL AND METHODS: We report the first case of pediatric lumbar primary aneurysmal bone cyst in which completely blood-less piecemeal total resection of the lesion was performed after intraoperative absolute alcohol intralesional sclerotherapy. RESULTS: Completely blood-less piecemeal total resection of the lumbar aneurysmal bone cyst was performed after intraoperative absolute alcohol intralesional sclerotherapy. CONCLUSION: Intraoperative absolute alcohol intralesional sclerotherapy is a very effective devascularizing adjunct for complete piecemeal resection of spinal aneurysmal bone cyst in children with limited blood volume.

Unusual presentation of aneurysmal bone cyst (ABC) in children: pediatric intracranial osteosarcoma with secondary ABC.

A 13-year-old female patient presented with painless vision loss and proptosis for 18 months. Imaging findings were highly suggestive of a supraorbital aneurysmal bone cyst (ABC) for which she underwent complete surgical excision. Postoperatively, she developed left hemiparesis. Computed tomography angiography (CTA) revealed right complete internal carotid arterial (ICA) thrombosis. This was managed conservatively, and she improved in hemiparesis over the next 3 weeks. Histopathology report revealed osteosarcoma with secondary ABC, for which she was referred for radiotherapy. At 1.5 months follow-up, the patient's left lower limb power improved to 4 + /5. She was walking without support, and her left upper limb power was 4/5.

A rare case of aneurysmal bone cyst of the anterior clinoid process in an 18-year-old female mimicking optic neuritis.

BACKGROUND: Aneurysmal bone cyst (ABC) is an uncommon, benign, vascular multicystic bony lesion that most frequently develops in the first two decades of life. The metaphysis of long bones, pelvic, and vertebral column are the most common locations. The precise underlying pathophysiology of ABCs formation remains unclear; however, it is believed that reactive processes subsequent to trauma or vascular disturbance may play an important role. Involvement of the skull base rarely occurs with a prevalence of up to 5% of intracranial ABCs. CASE PRESENTATIONS: An 18-year-old adolescent female with a history of progressive blurred vision since three months ago presented to our office. The brain and orbital MRI demonstrated no abnormal findings. After three months of glucocorticoid treatment with the diagnosis of multiple sclerosis, the visual impairment of the left eye deteriorated abruptly. The patient underwent an MRI and the imaging study demonstrated a well-defined 30 × 22 × 20-mm lesion at the anterior clinoid process with an extension to the optic canal and ethmoid sinus. The patient underwent pterional craniotomy, and the tumor was resected. The histopathological examination was suggestive of ABC. CONCLUSION: ABC and other conditions should be considered in young-age people with an early unilateral decline in vision and imaging studies should be obtained in early stages and during follow-ups.

Analysis of Diagnosis and Treatment Strategies for Primary Juvenile Psammomatoid Ossifying Fibroma Complicated With Primary Aneurysmal Bone Cyst.

BACKGROUND: Juvenile Psammomatoid Ossifying Fibroma (JPOF) is a type of noncancerous bone tumor that usually affects adolescents in the craniomaxillofacial area. Clinical manifestations are usually symptoms caused by the tumor's invasive compression of surrounding tissues. Aneurysmal Bone Cyst (ABC) is also a benign bone tumor, and it typically occurs in long bones and the spine. Only 2% to 3% of cases occur in the head and neck. Due to the rarity of this combination of clinical cases, clinicians face difficulties in comprehensively understanding this complex lesion. Therefore, a comprehensive review of the clinical manifestations and characteristic imaging findings is necessary for surgeons. CASE PRESENTATIONS: On April 6, 2019, a 13-year-old boy presented with left maxillofacial bulge and pain for 1 month. Magnetic resonance imaging of the paranasal sinuses showed an irregular hive-like mass signal in the left maxillary sinus, and cystic changes with fluid levels were seen in the lesion. After the initial diagnosis of JPOF with primary ABC, we decided to perform a facial mid-facial resection of maxillary sinus tumor to remove the tumor tissue. Finally, after 3 recurrences and 4 operations, there was no tumor recurrence for 20 months after the last operation, and the patient was still under continuous follow-up. CONCLUSIONS: This case provided a reference for the diagnosis and treatment of JPOF combined with ABC. In particular, a new understanding of the association between the two diseases and the management of recurrence were proposed, which had the potential to improve clinical understanding of this complicated condition.

[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.

[Aneurysmal Bone Cyst of the Rib:Report of a Case].

We report a case of an aneurysmal bone cyst (ABC) originating in a rib. A 34-year-old woman was admitted to our medical department for evaluation of left rib pain and an abnormal shadow in the left 7th rib observed on chest radiography. Computed tomography (CT) revealed an osteolytic lesion involving the left 7th rib. Positron emission tomography/CT showed slight fluorodeoxyglucose uptake in the lesion. We performed 7th rib resection with a 4 cm margin from the tumor, including the intercostal muscles in the 6th and 7th interspaces. Histopathological examination of the resected specimen showed multiple blood-filled spaces and fibrous trabeculae, which confirmed the diagnosis of an ABC. The patient's postoperative course was uneventful. Although rare, clinicians should consider ABCs in the differential diagnosis of rib tumors.

Giant cell tumor of bone with secondary aneurysmal bone cyst does not have a higher risk of local recurrence.

BACKGROUND: Fluid-fluid levels (FFLs) is found in 10%-16% of giant cell tumor of bone (GCTB), and the presence of FFLs raises the suspicion of GCTB with secondary aneurysmal bone cyst (ABC), which can lead to increased intraoperative bleeding and, blurring the operative field, be associated with a risk of local recurrence. The first objective of this study is to determine whether secondary ABC is associated with a higher risk of local recurrence after curettage in patients with GCTB of the extremities. The second objective of this study is to investigate the sensitivity, specificity, positive predictive value, and negative predictive value of the presence of FFLs detected on magnetic resonance imaging (MRI) to diagnose secondary ABC associated with GCTB. METHODS: Two hundred and eighty patients with GCTB of the extremities who underwent curettage at the authors' institutions between 1980 and 2021 were included in this study. RESULTS: Secondary ABC was found in 36 of 280 patients (12.9%) and local recurrence occurred in 66 of 280 patients (23.6%). Multivariate analysis showed no significant correlation between secondary ABC and local recurrence (hazard ratio [HR]: 1.87 (95% confidence interval [CI]: 1.00-3.53]; p = 0.051). Preoperative MRI revealed FFLs in 13 of 82 patients (15.9%). Sensitivity, specificity, positive predictive value, and negative predictive value of FFLs detected on preoperative MRI to diagnose secondary ABC were 36.8%, 90.5%, 53.8%, and 82.6%, respectively. CONCLUSION: The results of this study showed that secondary ABC does not increase the risk of local recurrence after curettage in patients with GCTB of the extremities. Although rare, FFLs were present in patients with GCTB and half of those with FFLs detected on preoperative MRI had secondary ABC.

Differentiation of giant cell tumours of bone, primary aneurysmal bone cysts, and aneurysmal bone cysts secondary to giant cell tumour of bone: using whole-tumour CT texture analysis parameters as quantitative biomarkers.

AIM: To determine whether computed tomography (CT) texture analysis parameters can be used as quantitative biomarkers to help differentiate giant cell tumour of bones (GCTs), primary aneurysmal bone cysts (PABCs), and aneurysmal bone cysts (ABCs) secondary to giant cell tumours of bone (GABCs). MATERIALS AND METHODS: One hundred and seven patients with 63 GCTs, 31 PABCs, and 13 GABCs were analysed retrospectively. All patients underwent preoperative CT. Two radiologists independently evaluated the qualitative features of the CT images and extracted texture parameters. Patient demographics, qualitative features, and texture parameters among GCTs, PABCs, and GABCs were compared statistically. Differences in these parameters between ABCs and GCTs were also assessed. ROC curves were obtained to determine optimal parameter values. RESULTS: The best preoperative CT parameters to differentiate GCTs, PABCs, and GABCs included one qualitative feature (location around the knee) and four texture parameters (95th percentile, maximum intensity, skewness, and kurtosis). Age and three texture parameters (5th percentile, inhomogeneity, and kurtosis) enabled statistically significant differentiation between GCTs and ABCs. Combination of the above four parameters generated the largest area under the ROC curve (AUC) for the differentiation of GCTs and ABCs. CONCLUSION: CT texture analysis parameters can be used as quantitative biomarkers for preoperative differentiation among GCTs, PABCs, and GABCs.

Langerhans cell histiocytosis with aneurysmal bone cyst-like changes: a case-based literature review.

BACKGROUND: Langerhans cell histiocytosis (LCH) is a neoplastic transformation of myeloid precursors that commonly presents as an osteolytic lesion of the long or flat bones in children. Aneurysmal bone cysts (ABC) are benign neoplasms that frequently affect the metaphysis of long bones and the spine, often revealing a rapidly expansile lesion with fluid-fluid levels. LCH with secondary ABC-like changes is a rare condition that has only been reported five times, with two presentations in the cranium. The aim of this paper is to review the etiology, clinical and radiographic presentations, and treatment of this condition, as well as to present a novel case on the topic. CASE DESCRIPTION: We describe a 5-year-old boy with a rapidly growing head mass and eye pain resulting in a diagnosis of LCH with secondary ABC-like changes. Radiography demonstrated an expansile, lytic lesion of the left parietal bone with fluid-fluid levels. A confirmatory diagnosis was made through histopathology, demonstrating an inflammatory, histiocytic infiltrate staining positive for CD1a, CD68, CD207 (Langerin), and S-100. The lesion was surgically excised, and the patient recovered without any complications. CONCLUSION: We present a novel case of LCH with secondary ABC-like changes managed with surgical excision. While a radiographic workup with multiple imaging modalities is helpful for diagnosis, a thorough immunohistochemical analysis is essential as imaging characteristics are variable and nonspecific. Furthermore, surgical excision should be considered first-line treatment for lesions involving the skull in surgically accessible areas as it is curative, alleviates symptoms, and allows for histopathological diagnosis.

Multimodality imaging features of USP6-associated neoplasms.

Since the discovery of USP6 gene rearrangements in aneurysmal bone cysts nearly 20 years ago, we have come to recognize that there is a family of USP6-driven mesenchymal neoplasms with overlapping clinical, morphologic, and imaging features. This family of neoplasms now includes myositis ossificans, aneurysmal bone cyst, nodular fasciitis, fibroma of tendon sheath, fibro-osseous pseudotumor of digits, and their associated variants. While generally benign and in many cases self-limiting, these lesions may undergo rapid growth, and be confused with malignant bone and soft tissue lesions, both clinically and on imaging. The purpose of this article is to review the imaging characteristics of the spectrum of USP6-driven neoplasms, highlight key features that allow distinction from malignant bone or soft tissue lesions, and discuss the role of imaging and molecular analysis in diagnosis.

Novel method to biopsy aneurysmal bone cysts in children.

PURPOSE: The thin and friable septations composing aneurysmal bone cysts (ABC) may be challenging to target for percutaneous biopsy. The purpose of this study was to describe and evaluate a novel method of ABC biopsy using endomyocardial biopsy forceps as an attempt to capture larger fragments of tissue for diagnosis. METHODS AND MATERIALS: This was a retrospective study performed over a 17-year period. Patients <18 years old who underwent percutaneous biopsy for a presumed ABC, based on pre-procedure imaging, were included. Medical records were reviewed to identify age, sex, lesion location, biopsy procedure details, complications, and pathology results. A diagnostic biopsy was defined as conclusive histologic confirmation. Inconclusive findings or findings suggestive of but not diagnostic of an ABC were treated as non-diagnostic, even if imaging and clinical findings were characteristic. Biopsy device selection and quantity of tissue obtained was at the discretion of the pediatric interventional radiologist. Fisher's exact test was used to compare the diagnostic yield of standard biopsies to those employing biopsy forceps. RESULTS: Twenty-three biopsies were performed in 18 patients (11 female) with a median age of 14.7 years (IQR 10.6-15.6). Lesions were located in the extremities (7, 30.4%), chest (6, 26.1%), pelvis (5, 21.7%), spine (4, 17.4%), and mandible (1, 4.3%). Specimens were obtained using a 13- or 15-gauge bone coring needle (11, 47.8%); 14-, 16-, or 18-gauge soft tissue needle (6, 26.1%); or a combination of bone and soft tissue (4, 17.4%) needles. Endomyocardial biopsy forceps were utilized in 7 cases (30.4%), 2 in which it was the only device used. Overall, a conclusive pathologic diagnosis was made in 13/23 (56.5%) biopsies. Of the diagnostic biopsies, 1 was a unicameral bone cyst and all others were ABCs. No malignancy was identified. Compared to the standard approach, the use of forceps was more likely to result in a diagnostic biopsy (40.0% vs 100.0%, p = 0.008). There were no complications. CONCLUSIONS: Endomyocardial biopsy forceps offer an additional, novel technique to biopsy presumed ABCs and may improve diagnostic yield.

Primary aneurysmal bone cyst of hands and feet: A series of 14 cases.

Aneurysmal bone cyst (ABC) is a relatively rare, benign bone tumor that occurs exceptionally in the hands and feet. The objective of this article is to present clinical, radiological, histopathological features and management of a series of 14 primary ABC cases in these unusual locations. Eight cases occurred in hands and six in feet. We present the first reported subungual case to occur in the hand. The average age of the patients was 26 years (range 7 to 49), with half being over the age of twenty at diagnosis. The male to female ration was 9:5. In radiological terms, ABC appeared as an expansive lesion with internal septa and without cortical disruption. Twelve cases displayed the classic multicystic morphology and two cases were of the solid variant. "Blue bone" was detected in 50 % of the specimens. Treatment consisted of curettage, excision, or amputation in all cases. Recurrence rate was observed in 35 % of the cases, with the similar ABC morphology as the original samples. New therapeutic options have been proposed on their own or in combination with surgery to reduce local recurrence rates.

Total en bloc spondylectomy of thoracic giant cell tumor with secondary aneurysmal bone cyst: case reports and review of literature.

Spinal giant cell tumor (GCT) combined with secondary aneurysmal bone cyst (ABC) is a locally aggressive primary bone tumor. Total en bloc spondylectomy has never been reported to treat thoracic GCT combined with secondary ABC. We retrospectively reviewed two cases of spinal GCT combined with secondary ABC. A 41-year-old male patient was presented with back pain due to irregular expansive bone destruction involving the T6 vertebral body and intraspinal space-occupying lesion. Total en bloc spondylectomy of T6 vertebra was performed with good neurological status after the surgery. A 29-year-old female patient was presented with right scapular region pain due to irregular expansive bone destruction involving the T5 vertebral body and intraspinal space-occupying lesion. Total en bloc spondylectomy of T5 vertebra was performed with good neurological status after the surgery. Adjuvant radiation therapy was applied after the surgery without local recurrence at the 12-month or 24-month follow-up. Spinal GCT combined with secondary ABC appears to have a high local recurrence rate. Therefore, total en bloc spondylectomy should be applied to treat thoracic GCT combined with secondary ABC.

Do's and Don'ts in Primary Aneurysmal Bone Cysts of the Proximal Femur in Children and Adolescents: Retrospective Multicenter EPOS Study of 79 Patients.

BACKGROUND: Aneurysmal bone cysts (ABC) are rare benign cystic bone tumors, generally diagnosed in children and adolescents. Proximal femoral ABCs may require specific treatment strategies because of an increased pathologic fracture risk. As few reports are published on ABCs, specifically for this localization, consensus regarding optimal treatment is lacking. We present a large retrospective study on the treatment of pediatric proximal femoral ABCs. METHODS: All eligible pediatric patients with proximal femoral ABC were included, from 11 tertiary referral centers for musculo-skeletal oncology (2000-2021). Patient demographics, diagnostics, treatments, and complications were evaluated. Index procedures were categorized as percutaneous/open procedures and osteosynthesis alone. Primary outcomes were: time until full weight-bearing and failure-free survival. Failure was defined as open procedure after primary surgery, >3 percutaneous procedures, recurrence, and/or fracture. Risk factors for failure were evaluated. RESULTS: Seventy-nine patients with ABC were included [mean age, 10.2 (±SD4.0) y, n=56 male]. The median follow-up was 5.1 years (interquartile ranges=2.5 to 8.8).Index procedure was percutaneous procedure (n=22), open procedure (n=35), or osteosynthesis alone (n=22). The median time until full weight-bearing was 13 weeks [95% confidence interval (CI)=7.9-18.1] for open procedures, 9 weeks (95% CI=1.4-16.6) for percutaneous, and 6 weeks (95% CI=4.3-7.7) for osteosynthesis alone ( P =0.1). Failure rates were 41%, 43%, and 36%, respectively. Overall, 2 and 5-year failure-free survival was 69.6% (95% CI=59.2-80.0) and 54.5% (95% CI=41.6-67.4), respectively. Risk factors associated with failure were age younger than 10 years [hazard ratios (HR)=2.9, 95% CI=1.4-5.8], cyst volume >55 cm 3 (HR=1.7, 95% CI=0.8-2.5), and fracture at diagnosis (HR=1.4, 95% CI=0.7-3.3). CONCLUSIONS: As both open and percutaneous procedures along with osteosynthesis alone seem viable treatment options in this weight-bearing location, optimal treatment for proximal femoral ABCs remains unclear. The aim of the treatment was to achieve local cyst control while minimizing complications and ensuring that children can continue their normal activities as soon as possible. A personalized balance should be maintained between undertreatment, with potentially higher risks of pathologic fractures, prolonged periods of partial weight-bearing, or recurrences, versus overtreatment with large surgical procedures, and associated risks. LEVEL OF EVIDENCE: Level IV, therapeutic study.

Pseudocysts of the jaw: a retrospective study of 41 cases from a single institution.

OBJECTIVE: The purpose of this retrospective study was to investigate and compare the clinical, radiographic, pathological, pathogenesis, and therapeutic features of simple bone cysts (SBCs) and aneurysmal bone cysts (ABCs) of the jaw. METHODS: 35 patients with SBCs and 6 patients with ABCs who received treatment at the Department of Oral and Maxillofacial Surgery, Zhejiang University School of Medicine from 2017 to 2022 were followed up and reviewed retrospectively. RESULTS: The study included 41 patients, accounting for 2.14% of all jaw pathologies, with 35 patients having SBCs and 6 patients having ABCs; their average ages were 26.63 ± 13.62 years and 17.83 ± 7.88 years, respectively. The prevalence of SBC and ABC did not differ significantly by sex. The mandible was the most vulnerable area to be involved. Only 5.71% (2/35) of patients with SBCs and 16.7% (1/6) of patients with ABCs reported histories of previous trauma in the same region of the pseudocysts. A total of 42.86% (15/35) of SBC cases and 66.67% (4/6) of ABC cases had malocclusions. The radiographic features of pseudocysts varied in shape, were associated with the root, and unilocular or multilocular. All patients had curettage with or without bone graft or substitute implantation, and recurrences did not occur in 94.29% (33/35) of SBC patients and 100% (6/6) of ABC patients after a mean follow-up time of 26.23 ± 15.47 months and 21.67 ± 19.75 months, respectively. CONCLUSIONS: Pseudocysts, including SBCs and ABCs, are benign osteolytic lesions without an epithelial lining that occur occasionally in the jaw, mostly in adolescents and young adults, and their incidence did not significantly differ by sex. The most vulnerable site of involvement is the mandible, and they are generally not overtly aggressive. Trauma has a less significant role in pseudocysts, but minor trauma, such as malocclusion, has the potential to influence pseudocyst development. The clinical presentation of pseudocysts lacks specificity, and most patients are asymptomatic and found incidentally during radiographs. Dental panoramic radiographs and CBCT cannot accurately distinguish between SBC and ABC, and the final diagnosis depends on pathological diagnosis. Curettage combined with bone grafting is currently the best treatment for both, with a 5.71% (2/35) recurrence rate for SBC and no recurrence found for ABC.

Large skull osteoblastoma presented as aneurysmal bone cyst (ABC).

Aneurysmal bone cysts (ABCs) are rare benign vascular bony lesions mostly encountered in young patients. These cysts can occur as primary lesions or, less frequently, secondary to other pathologies such as osteoblastomas. Skull ABCs are rare and can extend intracranially, presenting with hydrocephalus and bleeding. Here we illustrate the case of a 9-year-old male who presented with headache, nausea, and vomiting, without neurological deficit. Radiological investigations showed a soap-bubble lesion with mass effect over the right cerebellum. The patient underwent right sub-occipital craniotomy with marginal wide resection of the cystic lesion. The patient had excellent outcomes. The histopathological report was consistent with osteoblastoma with an aneurysmal bone cyst.

Solid-variant aneurysmal bone cysts in the craniofacial skeleton: the role of genomic analysis.

BACKGROUND: Solid variant aneurysmal bone cysts (SVABCs) are a rare but well-described subtype of ABCs. While classic ABCs are readily identified radiographically, SVABCs lack these characteristic radiographic features and thus have a wide differential diagnosis on presentation (including Ewing sarcoma, Langerhans cell histiocytosis, osteosarcoma, metastasis, and giant cell tumor). Genomic/molecular analyses are often necessary for the diagnosis of SVABCs, with USP6 rearrangements being a characteristic finding. We present two cases in which genomic analysis was critical in the diagnosis of SVABCs and revealed unique gene fusions that may provide insight into SVABC pathogenesis. CASE DESCRIPTIONS: Two 13-year old male children presented to our institution with new mass lesions involving the craniofacial skeleton. Magnetic resonance imaging (MRI) in both cases revealed predominantly solid, avidly enhancing masses, one of the squamous portion of the temporal bone, and the other arising from the sphenopalatine foramen with extension into the ipsilateral maxillary and ethmoid sinuses. Histopathology displayed predominantly solid morphology, and next generation sequencing (NGS) revealed a FAT1-USP6 gene fusion in the temporal lesion, and a MIR22HG-USP6 gene fusion in the maxillofacial lesion, the latter of which was not identified on fluorescence in situ hybridization (FISH). These findings were most consistent with a diagnosis of SVABC in each case. CONCLUSIONS: These two cases highlight novel gene fusions in atypically located SVABCs and emphasize the ability of NGS to more accurately and consistently identify USP6 gene fusions, particularly in SVABCs that may otherwise be indistinguishable from alternative pathologies.

Percutaneous image-guided treatment of aneurysmal bone cysts: is there a superior treatment option?

BACKGROUND: Aneurysmal bone cysts (ABCs) are often treated with intralesional surgery (curettage) with or without adjuvant treatments. Side effects and conflicting results regarding recurrence rates do not suggest one clearly superior therapy. Percutaneous therapeutic options including sclerotherapy and thermal ablation have gained popularity as potential alternatives. OBJECTIVE: The purpose of this retrospective review is to report this institution's experience and results of various image-guided minimally invasive treatments in a single institution series of cases referred to interventional radiology by orthopedic surgery after surgical failure or in patients with anatomically challenging ABCs. MATERIALS AND METHODS: This study identified all patients ≤18 years old who received percutaneous therapy for an ABC, including cryoablation, doxycycline sclerotherapy, microwave ablation or a combination of these modalities. Procedural details, complications, imaging follow-up and clinical follow-up were analyzed. RESULTS: A total of 21 patients received 41 procedures, with major complications seen in 7.7% (3/39) of procedures involving cryoablation or doxycycline sclerotherapy. Patients receiving cryoablation required an average of 1.7 procedures (median: 1 procedure, range: 1-4 procedures) while patients receiving doxycycline sclerotherapy required an average of 3 procedures (median: 2 procedures, range: 1-6 procedures). Patients were followed clinically and with computed tomography or magnetic resonance imaging (average: 23.9 months, range: 3.9-68.3 months). Follow-up imaging demonstrated improvement in 17 (85%) patients. Clinically, 93.8% (15/16) of patients who presented with fracture or pain had markedly reduced or absent pain as well as no fractures. CONCLUSION: Percutaneous image-guided treatment of ABCs demonstrates a favorable efficacy and safety profile. Adding cryoablation may lead to fewer total procedures than using doxycycline sclerotherapy alone.

Aneurysmal bone cyst of the pelvis and sacrum: a single-center study of 17 cases.

BACKGROUND: The aneurysmal bone cyst (ABC) is a benign, but locally aggressive cystic lesion of the bone. It usually occurs in the metaphysis of long bones of adolescents and young adults but can also affect the pelvis. METHODS: This single-center study is a retrospective review of 17 patients with primary ABCs of the pelvis. It examines the importance of polidocanol instillations as minimally invasive treatment option for ABCs of the pelvis compared to intralesional curettage or marginal resection. RESULTS: Seventeen patients with the diagnosis of a primary ABC of the pelvis were included in the study. Six patients were male (35%) and 11 patients female (65%); the mean age was 18 (9-49) years. The mean follow-up time was 50 months (12-136 months). The most common location of manifestation was the pubis (6; 35%), followed by the ilium (6; 35%), the sacrum (3; 18%) and the ischium (2; 12%). Eight patients were treated by intralesional curettage with the use of adjuvants, one patient by marginal resection, seven by sequential instillation of polidocanol and one patient by simple observation. Five patients received an additional transarterial embolization. After intralesional curettage local recurrence was detected in 4/8 cases (50%). After instillation therapy six patients (86%) had a stable disease without recurrence, only one patient (14%) had a persistent disease with need of additional treatment and was therefore converted to intralesional curettage without local recurrence in the follow-up. CONCLUSIONS: Sequential instillations of polidocanol are a promising, minimally invasive treatment method for ABCs of the pelvis and can be well combined with transarterial embolization.