[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.

[Pediatric neurosurgical treatment of aneurysmal bone cyst at the level of thoracic spine]. / Aneurysmás csontcysta gyermek-idegsebészeti megoldása a háti gerinc magasságában.

Aneurysmal bone cysts are benign but locally aggressive bone tumours, most often affecting children and young adults. In this case report, we present the clinical  picture of a 15-year-old boy with progressive, chronic back pain. An MRI of thoracic spine  confirmed a T2 cystic spinal tumour. After considering potential options surgical removal was our choice and gross total removal was achieved with T1-3 short-segment fixation. Aneurysmal bone cysts are often rapidly expanding lesions with vascular  transformation. In order to avoid irreversible damage, in addition to early diagnosis, it is necessary to carefully consider the therapeutic options, perform surgical removal and stabilization as necessary. In case of the presented patient, extensive surgical removal and short-segmentation were performed. At 18 months of follow-up, he had no complaints and was asymptomatic. Follow-up imaging studies showed no residual or recurrent tumour to date.

Aneurysmal bone cysts: A UK wide tumor center experience.

BACKGROUND AND OBJECTIVES: This multicenter retrospective series of consecutive extra-spinal aneurysmal bone cysts aims to identify risk factors for treatment failure. METHODS: Aneurysmal bone cysts treated within seven collaborating centers with over 12-months follow-up were eligible for inclusion. Survival analyses were performed to identify variables associated with recurrence using log-rank tests and Cox proportional hazard regression. RESULTS: One hundred and fifteen (M:F 60:55) patients were included. Median age at presentation was 13 years and median follow-up was 27 months. Seventy-five patients underwent surgical curettage and 27% of these required further intervention for recurrence. Of the 30 patients who underwent biopsy with limited percutaneous curettage as initial procedure, 47% required no further treatment. Patients under 13 years (log-rank p = 0.006, HR 2.3, p = 0.011) and those treated who had limited curettage (log-rank p = 0.001, HR 2.7, p = 0.002) had a higher risk of recurrence/persistence. CONCLUSIONS: There is a high risk of recurrence following surgical treatment for aneurysmal bone cysts and this risk is higher in young patients. However, the cyst heals in a substantial number of patients who have a limited curettage at the time of biopsy.

Use of Surgical Adjuvants Does Not Decrease Recurrence of Aneurysmal Bone Cysts in Surgical Intervention With Pediatric Patients.

BACKGROUND: Aneurysmal bone cysts (ABCs) are benign active tumors often requiring intralesional curettage with or without adjuvants. The primary aim of this study was to analyze whether recurrence is influenced by the use of surgical adjuvants in pediatric patients with ABCs. Secondary aims examined recurrence rates based on age, sex, and physeal contact. METHODS: A retrospective review was performed at a tertiary pediatric hospital from 2004 to 2020. Inclusion criteria consisted of patients treated surgically for histologically confirmed ABCs with a minimum of 6 months follow-up. Patients with treatment for a recurrent tumor or incomplete records were excluded. Patient demographics, location of the lesion, treatment technique, and incidence of recurrence were collected. Statistical analyses were performed using STATA. RESULTS: There were 129 patients (74 males and 55 females) with a mean age of 11.5 ± 4.1 years and an average follow-up of 29.0 ± 25.4 months. The most common locations for ABCs were the femur and tibia. Of the patients, 53.5% had tumors abutting the physis, 28.7% had no physeal contact, and 17.8% had insufficient imaging to evaluate physeal contact. Surgical adjuvants (high-speed burr, coagulation, liquid nitrogen, and/or hydrogen peroxide) were used in 91 of the 129 cases (70.5%). There was no significant difference in recurrence when comparing those who received an adjuvant and those who did not (25.3% vs 23.7%, P = 1.000). Physeal contact was also not significantly associated with recurrence ( P = 0.146). Finally, patients younger than 6 years old were significantly more likely to have recurrence compared with those 6 years old or older (66.7% vs 21.7%, P = 0.007). CONCLUSION: Our study found no association between the use of surgical adjuvants and the risk of recurrence after intralesional curettage for ABCs. Although our study did demonstrate that patients 6 years old or younger had an increased rate of recurrence, no significant association was found regarding physeal contact or sex. These data indicate that surgical adjuvant may not affect the recurrence rates of pediatric patients with ABCs. LEVEL OF EVIDENCE: Level III. This retrospective review compares rates of recurrence based on the choice of surgical adjuvant.

Does the preoperative neutrophil-to-lymphocyte ratio have a prognostic value in aneurysmal bone cysts?

OBJECTIVES: The aim of this study was to evaluate the prognostic value of neutrophil-to-lymphocyte ratio (NLR), lymphocyte-tomonocyte ratio (LMR), and platelet-to-lymphocyte ratio (PLR) in aneurysmal bone cysts (ABCs). PATIENTS AND METHODS: Between February 2001 and August 2019, a total of 86 patients (44 males, 42 females; mean age: 21.5±15.2 years; range, 2 to 73 years) with a histologically confirmed diagnosis of ABCs who did not receive cancer treatment previously and had a minimum follow-up period of 24 months were retrospectively analyzed. Data including age, sex, side, tumor location, pre-treatment complete blood count analysis results, preferred surgical method, follow-up period, presence of recurrence, and date of recurrence were recorded. Preoperative NLR, LMR and PLR values were calculated in all patients. RESULTS: The mean follow-up was 56.7±13.5 (range, 24 to 179) months. Forty-one (47.7%) ABCs were located in the lower extremities, 36 (41.8%) in the upper extremities, and nine (10.4%) in the pelvic girdle. A statistically significant difference was detected in the NLR values according to recurrence status (p=0.023). The PLR and LMR values were not significant for area under the curve, while NLR values were significant for recurrence. The cut-off value was determined as 2.054. Those with an NLR of ≥2.054 were found to have a 4.561-fold higher risk of recurrence than those with an NLR of <2.054 (odds ratio [OR]=4.561). CONCLUSION: Our study results suggest that NLR, which is the pre-treatment inflammatory index, is a prognostic factor in patients with ABCs. Although NLR alone is not decisive in patients with elevated NLR, it can be used to evaluate the clinical prognosis and recommend an appropriate treatment strategy.

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.

Secondary aneurysmal bone cyst of the frontal bone with fibrous dysplasia showing rapid expansion: a case report.

A 19-year-old woman presented with swelling of the left forehead without pain. She did not have any relevant past or family history. Computed tomography showed destruction of the outer cortex of the frontal bone. A solitary mass lesion with a fluid collection was detected with magnetic resonance imaging. Because the swelling of the left forehead had enlarged rapidly with osteolytic changes, surgical removal of the lesion was performed. The lesion appeared to be enveloped in a fibrous capsule. The soft lesion was removed from the frontal bone. The outer frontal bone was absent, although the inner frontal bone was preserved. Then, the frontal bone was resected with margins from the edge of the erosion. The dura mater under the lesion was intact. A cranioplasty was performed using titanium mesh. On histological examination, the trabecular bones revealed irregular shapes and arrangements, indicating fibrous dysplasia. There was a continuous high-cell-concentration pathological lesion outside the fibrous dysplasia. There were numerous cells, such as mononuclear cells, osteoclast-like multinucleated giant cells, foam cells, and red blood cells. The osteoclast-like multinucleated giant cells and other cells did not show significant nuclear atypia. Immunostaining with H3.3G34W was negative, and the ubiquitin-specific peptidase 6/Tre-2 gene showed no rearrangements. The histopathological diagnosis was secondary aneurysmal bone cyst with fibrous dysplasia. Additional postsurgical therapy was not performed. There has been no evidence of recurrence of the lesion for two years.

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.

Clínica, epidemiología e imagenología del quiste óseo aneurismático en el territorio craneofacial, análisis de sus patrones histopatólogicos: revisión narrativa / Clinical, epidemiology and imaging of the aneurysmal bone cyst in the craniofacial territory, analysis of its histopathological patterns: a narrative review

Introducción: El quiste óseo aneurismático (QOA) tiene una diversidad de características clínicase imagenológicas. Existe poca información respecto a la posible relación entre algunas de estas características y los patrones histopatológicos del QOA. El propósito de la presente revisión fue analizar la clínica, epidemiología e imagenología de casos de QOA, y determinar qué características podrían tener relación con algún tipo de patrón histopatológico del QOA en el territorio craneofacial. Materiales y métodos:Se realizó una búsqueda de casos de QOA en el territorio craneofacial publicados desde el año 2000, en PubMed, Scopus y Web of Science, mediante la búsqueda ("Aneurysmal bone cyst") AND ("Skull" OR "Jaw" OR "Mandible" OR "Maxilla"). Los casos debían tener información histopatológica, clínica, epidemiológica e imagenológica. Revisión: Se incluyó 40 artículos con 41 lesiones, siendo 34 de patrón clásico y 7 de patrón mixto-sólido (M-S). El patrón M-S se presentó mayoritariamente sin dolor y en el sexo masculino, mientras que el patrón clásico con dolor asociado y en el sexo femenino. Respecto a la imagenología, el patrón M-S se presentó sin límites definidos-corticalizados y generó perforación ósea con mayor frecuencia que el patrón clásico. Conclusiones: Los patrones histopatológicos del QOA tienen características clínicas, epidemiológicas e imagenológicas similares. Sin embargo, difieren en sexo, dolor asociado, límites definidos corticalizados y perforación ósea, lo que permitiría orientar al diagnóstico hacia un patrón histopatológico. (AU)

Introduction: The aneurysmal bone cyst (ABC) has a variety of clinical and imaging characteristics. There is little information regarding the possible relationship between some of these characteristics and its histopathological patterns. The aim of this review was to analyze the clinical, epidemiology and imaging characteristics of ABC cases, and determine what characteristics might be related to some type of histopathological pattern of ABC in the craniofacial territory. Materials and methods: A search was conducted for ABC cases in the craniofacial territory published since 2000, on PubMed, Scopus and Web of Science, by searching ("Aneurysmal bone cyst") AND ("Skull" OR "Jaw" OR "Mandible" OR "Maxilla"). Cases had to have histopathological, clinical, epidemiological, and imaging information. Review: 40 articles with 41 ABC lesions were included, with 34 being classic pattern and 7 mixed-solid (M-S). The M-S pattern was mostly painless and in males, while the classic pattern, with associated pain was mostly in females. Regarding imaging, the M-S pattern was without defined-corticated limits and with bone perforation more frequently than the classic pattern. Conclusions: Histopathological patterns of ABC have similar clinical, epidemiological and imaging characteristics. However, they differ in sex, associated pain, defined-corticated limits and bone perforation, which would allow the diagnosis to be directed towards a specific histopathological pattern. (AU)

Frequency of translocation of USP-6 in the aneurysmal bone cyst of the jaw.

BACKGROUND: This study aims to detect USP6 translocation in aneurysmal cysts located in the jaw and to give an overview of demographic data. METHODS: The present retrospective cohort study includes 10 patients who underwent surgery due to an aneurysmal cyst of the jaw in our hospital between 2002 and 2021. Unstained formalin-fixed and paraffin-embedded tissue sections cut at 4 µm thickness were subjected to USP6 FISH testing. RESULTS: All patients underwent surgical treatment. In four of ten patients (40%) USP-6-translocations have been found. CONCLUSION: Based on the study, it is hypothesized that the aneurysmal bone cyst of the jaw bone may be subject to a different pathomechanism than that of the long bones. Therefore, it seems conceivable that the primary cause of aneurysmal bone cysts in the jaw might differ.

The treatment of aneurysmal bone cysts.

PURPOSE OF REVIEW: Aneurysmal bone cysts are rare, locally aggressive bone tumors. Optimal treatment of ABCs is still matter of debate as therapies including sclerotherapy, selective arterial embolization and systemic treatment with denosumab are increasingly utilized, in addition to or instead of traditional curettage. The purpose of this review is to discuss current concepts and difficulties in diagnosing and treating primary ABCs, based on latest available literature. RECENT FINDINGS: In diagnostics, multiple new fusion partners of USP-6 have been described on next-generation sequencing specifically for primary ABCs. In a recent systematic review, failure rates of percutaneous injections and surgery were comparable. In a literature review, the use of denosumab seemed effective but resulted in multiple cases of severe hypercalcemia in children. SUMMARY: Accurately diagnosing primary ABC is crucial for treatment decisions. Curettage remains a valid treatment option, especially with adjuvant burring, autogenous bone grafting and phenolization. Percutaneous sclerotherapy represents a solid alternative to surgery, with polidocanol showing good results in larger studies. Systematic therapy with denosumab exhibits favorable results but should be reserved in the pediatric population for unresectable lesions, as it may result in severe hypercalcemia in children. When selecting a treatment option, localization, stability and safety should be considered.

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.

Talar metastasis of mucinous lung adenocarcinoma with fluid-fluid levels: a rare presentation mimicking a benign tumor.

The differential diagnosis of bone tumors in the talus is broad and includes both benign and malignant conditions. Metastases, although very rare, are one of these conditions. The typical nonspecific clinical and radiological presentations of metastases are a diagnostic challenge, and a high level of suspicion is needed in order to perform an adequate diagnostic approach. Moreover, they can present with features which have classically been associated with benign conditions such as fluid-fluid levels. We present a rare case of talar metastasis of a mucinous pulmonary adenocarcinoma that presented with fluid-fluid levels and was initially misdiagnosed as a giant-cell tumor with areas of secondary aneurysmal bone cyst transformation.

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.

Histopathogenesis of bone- and soft-tissue tumor spectrum with USP6 gene rearrangement: multiple partners involved in the tissue repair process.

Primary aneurysmal bone cyst, nodular fasciitis, myositis ossificans and related lesions as well as fibroma of tendon sheath are benign tumors that share common histological features and a chromosomal rearrangement involving the ubiquitin-specific peptidase 6 (USP6) gene. The tumorigenesis of this tumor spectrum has become complex with the identification of an increasing number of new partners involved in USP6 rearrangements. Because traumatic involvement has long been mentioned in the histogenesis of most lesions in the USP6 spectrum and they morphologically resemble granulation tissue or callus, we attempted to shed light on the function and role USP6 partners play in tissue remodelling and the repair process and, to a lesser extent, bone metabolism.

Clinical outcomes of tumors and tumor-like lesions located in the clavicle.

OBJECTIVES: The aim of this study was to examine the characterization of tumors and tumor-like lesions located in the clavicle and to present their clinical results. PATIENTS AND METHODS: Between January 2006 and December 2018, a total of 44 patients (25 males, 19 females; mean age: 36.2±21.8 years; range, 2 to 87 years) who were operated in our clinic for a clavicular lesion were included. Among 4,856 extremity tumors operated in our clinic between these years, 44 cases (0.9%) located in the clavicle were eligible. Demographic data, tumor types, location, surgical method, metastasis, survival analyzes and clinical results of these patients were reviewed retrospectively. According to the clavicle location, the patients were divided into groups according to their involvement in proximal, middle, lateral and more than one region. RESULTS: The most frequently involved site was the lateral edge of the clavicle, and the most common tumor was aneurysmal bone cyst. The most common malignant tumor was Ewing sarcoma and plasmacytoma (13.6%) and the most common surgical method in the clavicle was wide resection with 34.1%. Of the 38 primary clavicle tumors remaining after the metastatic lesions were removed, 21 (55%) were benign, while 17 (45%) were malignant. Aneurysmal bone cyst was most common in the group under 30 years of age, osteochondroma was most common in the 30-50 age group, and plasmacytoma was most common in those over 50 years of age. The mean musculoskeletal tumor society (MSTS) score of 15 patients (34.1%) who underwent clavicle resection was 79.4±6. CONCLUSION: We believe that a wide spectrum should be considered in the differential diagnosis of tumors located in the clavicle. Age is an important predictive factor for malignancy. We believe that resection should be applied without fear considering its effects on function and recurrence.

Synchronous polyostotic solid variant of aneurysmal bone cyst involving thoracic vertebrae and harboring a novel AHNAK::USP6 gene fusion. A case report and review.

Aneurysmal bone cyst (ABC) is a benign bone neoplasm that usually affects the metaphysis of long bones and the posterior elements of vertebral bodies. The rearrangement of USP6 gene is present in most of primary ABC cases. Synchronous polyostotic presentation is extremely rare. All of the eight reported cases in literature have a classic ABC histomorphology, including dilated-blood filled cystic spaces separated by fibrous septa and composed of variably cellular bland fibroblasts with scattered osteoclast-like giant cells and reactive new bone formation. Herein, we report a case of a 29-year-old female with a synchronous polyostotic solid variant of ABC involving her T7-T11 posterior elements of her thoracic vertebrae with a novel AHNAK::USP6 fusion, detected by next-generation sequencing (NGS). This case is distinguished by its synchronous polyostotic presentation, solid rather than classic ABC morphology and novel AHNAK::USP6 fusion, which has not been previously reported in ABC or in any mesenchymal bone tumor.

Clinicoradiological spectrum of primary aneurysmal bone cysts of the maxillofacial region: A series of 31 cases.

OBJECTIVES: The aim of the current study was to analyse the demographic, clinical and radiological features of primary aneurysmal bone cysts (ABCs) involving the maxillofacial region. METHODS: Histologically confirmed cases affecting the maxillofacial region were retrospectively reviewed over a 21-year period (2000-2021). Cases were collected from the archives of five Oral Pathology laboratories from three countries: South Africa, Guatemala and Brazil. The information was analysed, with emphasis on the clinical and radiological spectrum. RESULTS: Following the inclusion criteria, a total of 31 cases of primary ABCs were included in the study. A nearly equal male-to-female distribution was seen, with ABCs occurring in males at an earlier age compared to females. Localised swelling was the main clinical presentation. ABCs had a mandibular predominance, particularly in the posterior regions. All ABCs presented as blow-out expansile well-demarcated radiolucent lesions with the majority having a multilocular appearance. Cortical expansion was seen in 91% of cases with loss of cortical integrity being common (78%). CONCLUSION: Primary ABCs involving the maxillofacial region are extremely rare with the majority of current published literature consisting of isolated case reports. The current study is the first large series detailing the radiological features.

FDG PET/CT Image of Soft Tissue Aneurysmal Bone Cyst.

ABSTRACT: Soft tissue aneurysmal bone cyst is very rare. Herein, we report FDG PET/CT findings of aneurysmal bone cyst in a 19-year-old man. On conventional image, it presented as a paravertebral soft tissue mass with heterogeneous enhancement and rim eggshell-like calcification. On PET/CT, this solitary lesion had intense FDG uptake with an SUV max of 10.33. The final pathology supported a diagnosis of aneurysmal bone cyst. Our case suggests that soft tissue aneurysmal bone cyst should be regarded as a differential diagnosis of solitary paravertebral mass with intense FDG uptake.

[Giant cell-containing tumors of bone and differential diagnoses]. / Riesenzell-haltige Tumoren des Knochens und Differenzialdiagnosen.

Osteoclastic giant cells represent a common cellular component of lesions arising in bone. Highlighting this morphological finding, the current WHO classification of bone tumors defines a diagnostic group comprising aneurysmal bone cyst, giant cell tumor of bone and non-ossifying fibroma, which may display morphologic similarities while being distinct with regard to molecular and biological features. Starting with these tumors - putting a focus on lesions arising in bone - this article gives a survey of other (chondrogenic and osteogenic) tumors that frequently contain osteoclastic giant cells, which may, particularly in small biopsies, enter differential diagnosis. Overlapping features with selected giant cell-containing soft tissue tumors, which may be of differential diagnostic relevance in daily routine, are discussed.