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Introduction: The percentage of tumor necrosis is a crucial prognostic factor in osteosarcoma. Many studies adopt a 90 % cutoff based on osteoblastic osteosarcoma, but these findings are generalized to all conventional subtypes, including chondroblastic osteosarcoma. We sought to answer these questions: (1) Is tumor necrosis ≥90 % associated with better overall survival (OS) and disease-free survival (DFS) in osteoblastic and chondroblastic osteosarcoma? (2) Does the osteosarcoma subtype impact tumor necrosis? (3) Does the osteosarcoma subtype in "good" responders (tumor necrosis ≥90 %) affect OS and DFS?., Materials and Methods: We conducted a retrospective study of 156 patients with osteoblastic and chondroblastic osteosarcoma treated at our institution. All patients received a standardized chemotherapy protocol and underwent surgery with the goal of achieving negative margins (R0 resection). Propensity-score matching was performed to adjust for potential confounders. Kaplan-Meier survival analysis and Cox proportional hazards modeling were performed., Results: Patients with osteoblastic osteosarcoma and tumor necrosis ≥90 % had higher 5- and 10-year OS and DFS compared to those with necrosis <90 %. In chondroblastic osteosarcoma, a trend towards higher OS and DFS was seen in patients with tumor necrosis ≥90 %; this, however, was not significant. Chondroblastic osteosarcoma was not a risk factor for either tumor necrosis <90 % (p = 0.89) or tumor necrosis <70 % (p = 0.57). Patients with osteoblastic or chondroblastic osteosarcoma that were deemed "good" responders (tumor necrosis ≥90 %) had similar OS and DFS at the 5- and 10-year marks., Conclusion: Conventional osteosarcoma subtype was not a risk factor for "poor" response. Survival outcomes (OS and DFS) were similar for osteoblastic and chondroblastic osteosarcoma with good response to chemotherapy., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Myositis ossificans, a benign tumor composed of spindle cells and osteoblasts, can clinically and radiologically mimic osteosarcoma. While recognition and accurate diagnosis of myositis ossificans can be a challenge, this is critical as it may allow a conservative surgical approach to maximize functional outcomes. Herein, we present a patient with surface myositis ossificans confirmed genetically by the presence of COL1A1::USP6 gene fusion, along with a literature review. Due to the enhanced visualization of the bone matrix, computed tomography (CT) imaging may be a superior imaging modality to magnetic resonance (MR) imaging. Staged biopsies with samples obtained from the periphery and center of the lesions may allow pathologists to discern the zonal distribution histologically. Furthermore, immunohistochemistry fluorescence in situ hybridization and molecular testing can aid in the distinction of myositis ossificans from mimics. Because of their resemblance to other bone tumors, these cases of myositis ossificans highlight the importance of a multidisciplinary approach integrating clinical, radiologic, and pathologic analysis and involving serial imaging, sampling, and judicious use of ancillary immunohistochemical and molecular testing., (© 2024 Scandinavian Societies for Pathology, Medical Microbiology and Immunology.)

Primary bone tumours can pose diagnostic problems due to their overlapping radiologic and histologic features. Given the recent advancement in our understanding of the biology of bone tumours, multiple immunohistochemical and molecular markers have been devised to aid in their diagnosis. This review provides brief updates on select bone tumours, including chondrosarcomas, benign chondrogenic tumours, osteosarcomas, benign osteogenic tumours, fibroosseous lesions, vascular tumours, osteoclastic giant cell-rich or cystic tumours, chordoma, adamantinoma, small round blue cell sarcomas, and others. We discuss their salient molecular features and novel immunohistochemical correlates, along with some tips to avoid common diagnostic pitfalls., (© 2022 John Wiley & Sons Ltd.)

Aberrant methylation of genomic DNA has been reported in many cancers. Specific DNA methylation patterns have been shown to provide clinically useful prognostic information and define molecular disease subtypes with different response to therapy and long-term outcome. Osteosarcoma is an aggressive malignancy for which approximately half of tumors recur following standard combined surgical resection and chemotherapy. No accepted prognostic factor save tumor necrosis in response to adjuvant therapy currently exists, and traditional genomic studies have thus far failed to identify meaningful clinical associations. We studied the genome-wide methylation state of primary tumors and tested how they predict patient outcomes. We discovered relative genomic hypomethylation to be strongly predictive of response to standard chemotherapy. Recurrence and survival were also associated with genomic methylation, but through more site-specific patterns. Furthermore, the methylation patterns were reproducible in three small independent clinical datasets. Downstream transcriptional, in vitro, and pharmacogenomic analysis provides insight into the clinical translation of the methylation patterns. Our findings suggest the assessment of genomic methylation may represent a strategy for stratifying patients for the application of alternative therapies., (© 2022. The Author(s).)

Background: MicroRNAs are small, noncoding RNAs that regulate the expression of posttranslational genes. The presence of some specific microRNAs has been associated with increased risk of both local recurrence and metastasis and worse survival in patients with osteosarcoma. Pathologic fractures in osteosarcoma are considered to be more the manifestation of a neoplasm with a more aggressive biological behavior than the cause itself of worse prognosis. However, this has not been proved at the biological or molecular level. Currently, there has not been a microRNA profiling study of patients who have osteosarcoma with and without pathologic fractures that has described differences in terms of microRNA profiling between these two groups and their correlation with biologic behavior., Questions/purposes: (1) In patients with osteosarcoma of the extremities, how do the microRNA profiles of those with and without pathologic fractures compare? (2) What relationship do microRNAs have with local recurrence, risk of metastasis, disease-specific survival, and overall survival in osteosarcoma patients with pathologic fractures?, Methods: Between 1994 and 2013, 217 patients were diagnosed and treated at our institution for osteosarcoma of the extremities. Patients were excluded if (1) they underwent oncologic resection of the osteosarcoma at an outside institution (two patients) or (2) they were diagnosed with an extraskeletal osteosarcoma (29 patients) or (3) they had less than 1 year of clinical follow-up and no oncologic outcome (local recurrence, metastasis, or death) (four patients). A total of 182 patients were eligible. Of those, 143 were high-grade osteosarcomas. After evaluation of tumor samples before chemotherapy treatment, a total of 80 consecutive samples were selected for sequencing. Demographic and clinical comparison between the sequenced and non-sequenced patients did not demonstrate any differences, confirming that both groups were comparable. Diagnostic samples from the extremities of 80 patients with high-grade extremity osteosarcomas who had not yet received chemotherapy underwent microRNA sequencing for an ongoing large-scale osteosarcoma genome profiling project at our institution. Six samples were removed after a second look by a musculoskeletal pathologist who verified cellularity and quality of samples to be sequenced, leaving a total of 74 patients. Of these, two samples were removed as they were confirmed to be pelvic tumors in a second check after sequencing. The final study sample was 72 patients (11 patients with pathologic fractures and 61 without). Sequencing data were correlated with fractures and local recurrence, risk of metastasis, disease-specific survival, and overall survival through Kaplan-Meier analyses., Results: Several microRNAs were expressed differently between the two groups. Among the markers with the highest differential expression (edgeR and DESeq algorithms), Hsa-mIR 656-3p, hsa-miR 493-5p, and hsa-miR 381-3p were upregulated in patients with pathologic fractures, whereas hsa-miR 363, hsa-miR 885-5p, and has-miR 20b-5p were downregulated. The highest differential expression fracture and nonfracture-associated microRNA markers also distinguished groups of patients with different metastasis risk, a well as different disease-specific and overall survival. Furthermore, the profile of pathologic fractures demonstrated a higher differential expression for microRNA markers that were previously associated with a higher risk of metastasis and lower survival rates in patients with osteosarcoma., Conclusions: In patients who have osteosarcoma, the microRNA profiles of those with pathologic fractures are different than of patients without pathologic fractures. The highest differential expression mircroRNA molecules in patients with pathologic fractures predict also higher risk of metastatic disease as well as worse disease-specific survival and overall survival. Furthermore, we found higher differential expression of microRNAs in the pathologic fracture group previously associated with poor prognosis. The higher risk of metastasis and poorer overall survival in patients with pathologic fractures is inherent to tumor aggressive biologic behavior. It is plausible that the fracture itself is not the direct cause of worse prognosis but another manifestation of tumor biologic aggressiveness. Identification of these molecules through liquid biopsies may help to determine which patients may benefit from surgery before fractures occur. The same technology can be applied to identify patterns of response to conventional chemotherapy, assisting in more specific and accurate systemic therapy., Level of Evidence Level: III, prognostic study.

Giant cell tumor (GCT) of bone is a locally aggressive benign neoplasm characterized by an abundance of osteoclastic giant cells that are induced by the neoplastic mononuclear cells; the latter express high levels of receptor activator of nuclear factor κ-B ligand (RANKL). Denosumab, a RANKL inhibitor, which is clinically used to treat GCT, leads to a marked alteration in the histologic appearance of the tumor with giant cell depletion and new bone deposition, leading to substantial histologic overlap with other primary tumors of bone. Most significantly, denosumab-treated GCT (tGCT) with abundant bone deposition may mimic de novo osteosarcoma, or GCT that has undergone malignant transformation. To histologically characterize tGCT, we identified 9 cases of GCT biopsied or resected after denosumab treatment. tGCT cases included 16 specimens from 9 patients including 6 female and 3 male individuals aged 16 to 47 (median 32) years. Duration of treatment varied from 2 to 55 months. We compared these tumors with malignant neoplasms arising in GCTs (n=9). The histology of tGCT was variable but appeared to relate to the length of therapy. All tGCTs showed marked giant cell depletion. Early lesions were highly cellular, and the combination of cellularity, atypia, and haphazard bone deposition caused the lesion to resemble high-grade osteosarcoma. Unlike de novo high-grade osteosarcoma or malignancies arising in GCT, however, tGCT showed less severe atypia, reduced mitotic activity, and lack of infiltrative growth pattern. Tumor in patients on prolonged therapy showed decreased cellularity and abundant new bone, deposited as broad, rounded cords or long, curvilinear arrays. The latter morphology was reminiscent of low-grade central osteosarcoma, but, unlike low-grade central osteosarcoma, tGCT was negative for MDM2 and again lacked an infiltrative growth pattern. Overall, tGCT may have a wide range of morphologic appearances. Because the treated tumors bear little resemblance to their pretreatment counterparts, careful attention to the history of denosumab administration is crucial to avoid a misdiagnosis with an important impact on therapy. Unlike malignant GCTs, tGCTs lack significant nuclear atypia, mitotic activity, and infiltration of preexisting bone, but instead show a unique pattern of intralesional bone deposition.

Low-grade extraskeletal osteosarcoma is a rare tumor that may arise de novo or following radiation therapy. Because of the low-grade histology, it may be misdiagnosed as a benign lesion. We present a case of a 59-year-old man with a past history of radiotherapy for papillary carcinoma of the thyroid, presenting 16 years later with a low-grade extraskeletal osteosarcoma of the neck. The patient was treated with surgical excision and is disease free after 12 months of follow-up. The prognosis for patients with low-grade extraskeletal osteosarcoma is relatively good when compared with high-grade sarcomas. While there is a report of a low-grade extraskeletal osteosarcoma arising following radiotherapy for a benign condition, to the best of our knowledge this is the first reported case of a low-grade extraskeletal osteosarcoma occurring following radiotherapy for thyroid cancer, and the only case reported in the soft tissue of the head and neck region., (© The Author(s) 2015.)

Programmed cell death ligand 1 (PDL1, also known as B7H1) is a cell-surface protein that suppresses the cytotoxic CD8(+) T-cell-mediated immune response. PDL1 expression and its clinical relevance in sarcomas are not well understood. Therefore, we sought to measure RNA expression levels for PDL1 in 38 clinically annotated osteosarcoma tumor samples and aimed to determine if PDL1 expression correlates with clinical features and tumor-infiltrating lymphocytes (TIL). Quantitative real-time RT-PCR for PDL1 was optimized in 18 cell lines, of which 5 were osteosarcoma derived. qRT-PCR results were validated via flow cytometry and immunohistochemistry (IHC) in select cell lines. Total RNA was isolated from 38 human osteosarcoma samples for qRT-PCR analysis. Clinical data were sorted, and significance was determined by the Student t test. TILs were examined in patient samples by tissue microarray hematoxylin-eosin staining. We confirmed the constitutive PDL1 mRNA expression in cell lines by qRT-PCR, flow cytometry, and IHC. Across human osteosarcoma samples, PDL1 mRNA gene expression ranged over 4 log (>5,000-fold difference). Relative expression levels were evaluated against clinical factors such as age/gender, metastasis, recurrence, chemotherapy, percentage of necrosis, and survival; no significant associations were identified. The presence of TILs was associated with high PDL1 expression (R(2) = 0.37; P = 0.01). In summary, we developed an RNA-based assay to determine PDL1 expression levels, and we show, for the first time, that high levels of PDL1 are expressed in a subset of osteosarcoma, and PDL1 expression is positively correlated with TILs. Multiple agents targeting PD1/PDL1 are in clinical development, and this may be a novel immunotherapeutic strategy for osteosarcoma clinical trials., (©2014 American Association for Cancer Research.)

Distinguishing chondrosarcoma from chondroblastic osteosarcoma can be difficult and highly subjective, especially on a small biopsy specimen. This distinction is critical in determining the most accurate prognosis and appropriate treatment modality, as adjuvant chemotherapy with surgery is standard treatment for osteosarcoma, whereas chondrosarcoma is generally treated by surgical excision alone. Cartilaginous neoplasms have recently been shown to frequently (56%) harbor gene mutations in the metabolic enzymes isocitrate dehydrogenase 1 (IDH1) and IDH2 (IDH1>IDH2), whereas other mesenchymal tumors lack these genetic aberrations. We investigated whether the presence of IDH1/2 mutations can be used to distinguish chondrosarcoma from chondroblastic osteosarcoma. Tumors including 25 predominantly high-grade chondrosarcomas and 65 osteosarcomas (44 chondroblastic osteosarcomas and 21 mixed osteosarcomas with a chondroblastic component) were evaluated, and a total of 59 cases (66%) were suitable for genotyping. Mutational analysis was performed using a multiplexed polymerase chain reaction genotyping platform to query for hotspot mutations in the genes IDH1 at codon R132. IDH1-negative cases underwent Sanger sequencing of IDH2 exon 4. No osteosarcomas (0/36) and 61% of chondrosarcomas (14/23) harbored a somatic mutation in IDH1/2, with the majority (86%) of mutations found in the IDH1 gene. IDH1/2 mutation analysis appears to be a promising biomarker for the distinction of chondrosarcoma from chondroblastic osteosarcoma. A positive result strongly favors the diagnosis of chondrosarcoma over chondroblastic osteosarcoma. The presence of IDH1/2 mutations can also help confirm the diagnosis of dedifferentiated chondrosarcoma when the tumor displays osteosarcomatous differentiation.

Well-differentiated osteosarcoma of the jaw bones is rare, and is often confused with a variety of benign fibroosseous lesions. To better understand its clinicopathologic features, we reviewed our experience with 15 cases. The patients included 7 males and 8 females (age range 14 to 66 y; mean 42.8 y). Six of the tumors arose in the mandible, and 9 in the maxilla. Microscopically, the tumors were infiltrative, relatively hypocellular, and consisted of monomorphic, minimally atypical spindle cells that were usually arranged in fascicles. The tumor cells were intimately related to the surfaces of elongated trabeculae of neoplastic woven bone that lacked osteoblastic rimming. Nine patients were treated with wide excision, 2 patients with marginal excision, and 2 patients with excision and radiation therapy. After definitive therapy, there were no reports of recurrence or metastasis over an average follow-up of 34 months (range 1 to 80 mo). Well-differentiated gnathic osteosarcoma is a low-grade malignancy that may be successfully treated with wide local excision. The prognosis in our series was excellent.

Background and objectives: Bone tumours are relatively rare and, as a consequence, treatment in a centre with expertise is required. Current treatment guidelines also recommend review by a specialised pathologist. Here we report on international consensus‐based datasets for the pathology reporting of biopsy and resection specimens of bone sarcomas. The datasets were produced under the auspices of the International Collaboration on Cancer Reporting (ICCR), a global alliance of major (inter‐)national pathology and cancer organisations. Methods and results: According to the ICCR's process for dataset development, an international expert panel consisting of pathologists, an oncologic orthopaedic surgeon, a medical oncologist, and a radiologist produced a set of core and noncore data items for biopsy and resection specimens based on a critical review and discussion of current evidence. All professionals involved were bone tumour experts affiliated with tertiary referral centres. Commentary was provided for each data item to explain the rationale for selecting it as a core or noncore element, its clinical relevance, and to highlight potential areas of disagreement or lack of evidence, in which case a consensus position was formulated. Following international public consultation, the documents were finalised and ratified, and the datasets, including a synoptic reporting guide, were published on the ICCR website. Conclusion: These first international datasets for bone sarcomas are intended to promote high‐quality, standardised pathology reporting. Their widespread adoption will improve the consistency of reporting, facilitate multidisciplinary communication, and enhance comparability of data, all of which will help to improve management of bone sarcoma patients. [ABSTRACT FROM AUTHOR]

The diagnosis and treatment of a 32-year-old man with a type of bone cancer called osteosarcoma in his lower jaw are reviewed. Osteosarcoma is a rare cancer and only occurs in the jaw in 10% of all cases. The patient was successfully treated with surgery, chemotherapy, and radiation.

BACKGROUND Histologic response to chemotherapy has been shown to be an independent prognostic factor in patients with osteosarcoma and Ewing sarcoma. However, in patients with soft tissue sarcoma (STS), the prognostic impact of histologic response to chemotherapy is less clear. In the current study, the authors sought to determine the prognostic significance of treatment-induced pathologic necrosis in patients receiving neoadjuvant chemoradiotherapy for STS. METHODS Between 1989 and 2011, a total of 113 patients with grade 2 or 3 (graded according to the National Cancer Institute grading system using 3 tiers) extremity or truncal STS were identified who received neoadjuvant interdigitated chemoradiotherapy according to protocol followed by surgery. The extent of tumor necrosis in the resected specimens was quantified and correlated with outcome. RESULTS The median tumor necrosis rate was 90%, and 103 patients (91%) received all 3 cycles of planned neoadjuvant chemotherapy. The likelihood of achieving ≥95% necrosis was not related to the number of preoperative cycles of chemotherapy received but was found to be related to tumor histology (62% for malignant fibrous histiocytoma vs 0% for synovial sarcoma [ P<.001]; 56% for myxoid liposarcoma vs 0% for synovial sarcoma [ P = .002]). At a median follow-up of 6 years, there were no statistically significant differences noted in the 5-year local control, disease-specific survival, and overall survival rates for patients with ≥95% necrosis (50 patients; 44%) and <95% necrosis (63 patients; 56%), even when stratifying by histology. CONCLUSIONS In a homogeneous population of patients with high-grade extremity and truncal STS who were treated with neoadjuvant chemoradiotherapy, the extent of pathologic tumor necrosis did not correlate with outcome. Cancer 2014;120:3676-3682. © 2014 American Cancer Society. [ABSTRACT FROM AUTHOR]

The article describes the case of a 14-year-old boy with abnormal bones and a sacral mass. The boy was examined with an antalgic gait with a truncal lurch to the right side and a slight curvature of the lower lumbar spine. He was diagnosed with bone-forming tumor of the sacrum which is characterized by Doctor Richard M. Terek as an aggressive osteoblastoma of the sacrum. An atypical, bone-forming tumor with an appearance of osteosarcoma was detected in a computerized tomography (CT)-guided biopsy of the sacral lesion.