MDM2 and CDK4 expression in periosteal osteosarcoma

Soft Tissue Sarcomas with Chromosomal Alterations in the 12q13-15 Region: Differential Diagnosis and Therapeutic Implications

The chromosomal region 12q13-15 is rich in oncogenes and contains several genes involved in the pathogenesis of various mesenchymal neoplasms. Notable genes in this region include MDM2, CDK4, STAT6, DDIT3, and GLI1. Amplification of MDM2 and CDK4 genes can be detected in various mesenchymal and nonmesenchymal neoplasms. Therefore, gene amplification alone is not entirely specific for making a definitive diagnosis and requires the integration of clinical, radiological, morphological, and immunohistochemical findings. Neoplasms with GLI1 alterations may exhibit either GLI1 rearrangements or amplifications of this gene. Despite the diagnostic implications that the overlap of genetic alterations in neoplasms with changes in genes within the 12q13-15 region could create, the discovery of coamplifications of MDM2 with CDK4 and GLI1 offers new therapeutic targets in neoplasms with MDM2/CDK4 amplification. Lastly, it is worth noting that MDM2 or CDK4 amplification is not exclusive to mesenchymal neoplasms; this genetic alteration has also been observed in other epithelial neoplasms or melanomas. This suggests the potential use of MDM2 or CDK4 inhibitors in neoplasms where alterations in these genes do not aid the pathological diagnosis but may help identify potential therapeutic targets. In this review, we delve into the diagnosis and therapeutic implications of tumors with genetic alterations involving the chromosomal region 12q13-15, mainly MDM2, CDK4, and GLI1.

Osteogenic sarcomas of the hands: A case series with emphasis in its peculiarities and literature review

AIM

To present our experience on osteosarcomas of the hands and review the existing literature pertaining osteosarcomas in this extremely rare location.

METHODS

and results: Seven cases of osteosarcomas of the hands were reviewed, and a literature search of all primary osteosarcomas of the hands was performed. All tumors occurred in adults (mean age, 41 years) and were located mainly around the metacarpophalangeal joints. All patients presented with localized long-lasting pain as main symptom. The mean size at diagnosis was 33 mm. Three tumors were low-grade central osteosarcomas, 1 low-grade central chondroblastoma-like osteosarcoma and 3 high-grade osteosarcomas. All tumors were positive for mouse double-minute 2 homolog (MDM2) immunohistochemistry. Three cases yielded results with fluorescence in-situ amplification for MDM2 (12q15)/CEP12. At last follow-up, one patient with a high-grade osteosarcoma was dead of disease. The literature review revealed similar demographic and site distribution of osteosarcomas within the hands than our series and an unusually high proportion of low-grade central and parosteal osteosarcomas when compared to the proportion of these infrequent neoplasms in the whole skeleton.

CONCLUSIONS

osteosarcomas of hands present in older individuals compared to the population affected by conventional osteosarcomas of all sites. Importantly from a diagnostic, therapeutic and prognostic points of view, around 40% of osteosarcomas of the hands are low-grade osteosarcomas of the central or parosteal types.

Effect of adjuvant chemotherapy on periosteal osteosarcoma: a systematic review

BACKGROUND AND OBJECTIVE

The effects of adjuvant chemotherapy on periosteal osteosarcoma are controversial. Therefore, we conducted a systematic review of studies comparing mortality, local recurrence, distant metastasis and secondary malignancy incidence among patients who underwent surgery and (neo-) adjuvant chemotherapy or surgery alone for periosteal osteosarcoma without distant metastases at diagnosis.

METHODS

Of the 210 studies identified in the search, 13 were included in this study, involving 291 patients with periosteal osteosarcoma in total.

RESULTS

The mortality rates in the surgery and (neo-) adjuvant chemotherapy and surgery alone groups were 11.3% (8/71) and 16.3% (16/98), respectively. The overall pooled odds ratio was 0.89 (P = 0.800). The local recurrence rate in the surgery and (neo-) adjuvant chemotherapy group was 12.1% (8/66), while that in the surgery alone group was 17.6% (13/74). The overall pooled odds ratio was 1.31 (P = 0.601). The distant metastasis rate in the surgery and (neo-) adjuvant chemotherapy group was 15.2% (10/66) and that in the surgery alone group was 10.8% (8/74). The overall pooled odds ratio was 1.51 (P = 0.444). The incidence of secondary malignancy in the surgery and (neo-) adjuvant chemotherapy group was 7.6% (9/118) and that in the surgery alone group was 2.7% (2/74). The overall pooled odds ratio was 2.29 (P = 0.187).

CONCLUSIONS

Adjuvant chemotherapy did not appear to improve the prognosis of patients with periosteal osteosarcoma. No association was found between the use of adjuvant chemotherapy and development of secondary malignancies.

Clinicopathological value of the upregulation of cyclin-dependent kinases regulatory subunit 2 in osteosarcoma

Background

Cyclin-dependent kinase subunit 2 (CKS2) is a member of cyclin dependent kinase subfamily and the relationship between CKS2 and osteosarcoma (OS) remains to be further analyzed.

Methods

80 OS and 41 non-tumor tissue samples were arranged to perform immunohistochemistry (IHC) to evaluate CKS2 expression between OS and non-tumor samples. The standard mean deviation (SMD) was calculated based on in-house IHC and tissue microarrays, and exterior high-throughput datasets for further verification of CKS2 expression trend in OS. The effect of CKS2 expression on clinicopathological parameters of OS patients, and single-cell in OS tissues was analyzed through public high-throughput datasets and functional enrichment analysis was conducted for co-expression genes of CKS2 in accordance with weighted correlation network analysis.

Results

A total of 217 OS samples and 87 non-tumor samples (including tissue and cell line) were obtained from in-house IHC, microarrays and exterior high-throughput datasets. The analysis of integrated expression status demonstrated up-regulation of CKS2 in OS (SMD = 1.57, 95%CI [0.27–2.86]) and the significant power of CKS2 expression in distinguishing OS samples from non-tumor samples (AUC = 0.97 95%CI [0.95–0.98]). Clinicopathological analysis of GSE21257 indicated that OS patients with higher CKS2 expression was more likely to suffer OS metastasis. Although Kaplan–Meier curves showed no remarkable difference of overall survival rate between OS patients with high and low-CKS2, CKS2 was found up-regulated in proliferating osteosarcoma cells. Co-expression genes of CKS2 were mainly assembled in function and pathways such as cell cycle, cell adhesion, and intercellular material transport.

Conclusions

In summary, up-regulation of CKS2 expression in OS tissue was found through multiple technical approaches. In addition, scRNA-seq and co-expression analysis showed that CKS2 may have an impact on important biological process linked with cell cycle, cell adhesion, and intercellular material transport. Present study on CKS2 in OS indicated a promising prospect for CKS2 as a biomarker for OS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01234-8.

Osteosarcoma: Old and New Challenges

Diagnosis of osteosarcoma can be challenging because of its diverse histological patterns and the lack of diagnostic biomarkers for most examples. This review summarizes the key pathologic findings of osteosarcoma subtypes (high-grade central, parosteal, low-grade central, periosteal, high-grade surface, and secondary) with an emphasis on describing and illustrating histological heterogeneity to help general pathologists. Differential diagnoses are listed for each entity, and histological subtype and distinguishing features, including molecular genetic findings (eg, MDM2, IDH, H3F3A, FOS, and USP6), are discussed. The review also covers recently established and emerging concepts and controversies regarding osteosarcoma.

Primary synovial sarcoma of bone: A retrospective analysis of 25 patients

AIMS

To evaluate diagnostic accuracy of SSX and SSX-SS18 antibodies in decalcified surgical specimens and outcome of synovial sarcomas (SS) of bone.

METHODS AND RESULTS

Twenty-five cases were classified as bone SS (prevalence 0.32% among malignant primary bone sarcoma). Median age was 34 years (range 9 -79) . 24/25 patients presented with non-metastatic tumors, one with lung metastases. The majority of tumors involved the long bones of extremities with metaphyseal origin. Mean size of the tumor was 7.1 cm. 20 cases (80%) were monophasic and 5 (20%) biphasic. SS18-SSX fusion-specific antibody had 92% sensitivity and 99% specificity for primary bone SS, whereas SSX C-terminus antibody had 100% sensitivity and 94% specificity. FISH analysis was feasible in 9 (36%) cases and detected SS18 rearrangement in all 9 cases. All patients underwent surgical removal of their primary tumor, with adequate margins in 18 (72%) patients. Chemotherapy with metothrexate, cisplatin, doxorubicin, ifosfamide was used in the 7 patients. Two patients with inadequate surgical margins received radiotherapy. With a median follow-up of 80 months (range 6-428), 5-year and 10-year overall survival (OS) were 66.6% and 47.9% respectively and 5-and 10-years disease-free survival (DFS) were 36.8% (95% C.I.: 18.0-55.7%), and 32.2% (95% C.I.: 14.6-51.2%) respectively A significant improvement in 10-years DFS in patients undergoing chemotherapy as compared with patients who did not was observed (p 0.039).

CONCLUSIONS

Our series highlights the utility of SS18-SSX fusion-specific and SSX C-terminus antibodies to support the diagnosis of SS, Adjustment chemotherapy was associated with improved prognosis in this series.

Parosteal osteosarcoma with a manifestation of subperiosteal low-grade central osteosarcoma

We report the peculiar case of a parosteal osteosarcoma arising beneath the periosteum in a 12-year-old boy. He complained of difficulty in left knee flexion. Plain radiography showed a uniformly dense mineralized mass in the bone cortex and parosteal ossified nodules at the metaphysis and diaphysis of the left distal femur. Periosteal reaction was not evident. Uniquely, plain radiography had a smooth outline and revealed gradually thickening mass toward the center. Histologically, the tumor showed a proliferation of spindle-shaped cells with parallel-oriented dense bone trabeculae and hyaline cartilaginous tissue disclosing mild atypia. The periosteum was inverted along the polypoid mass, but there was no periosteum at the top. Immunohistochemically, the spindle cells, including those at the top of the polypoid mass, and cartilaginous cells were positive for MDM2 and CDK4. MDM2 gene amplification was detected in these cells by fluorescence in situ hybridization. Despite the peculiar feature of plain radiography, the lesion was diagnosed as parosteal osteosarcoma. This case report presents a case of parosteal osteosarcoma arising beneath the periosteum, although it is postulated to arise in the outer layer of the periosteum. The unique radiographic findings in this case suggest an association of parosteal osteosarcoma with vigorous bone growth before closure of the growth plate.

Exosomal PD-L1 and N-cadherin predict pulmonary metastasis progression for osteosarcoma patients

BACKGROUND

Recent studies indicated that exosomal programmed death-ligand 1 (PD-L1) derived from cancers could induce immunosuppression and tumor pathogenesis. However, it is unclear how exosomes influence osteosarcoma (OS) progression and whether PD-L1 also exists in serum exosomes (Sr-exosomes) of patients with osteosarcoma. We examined serum exosomes from 70 OS patients, 9 patients with benign tumors and 22 healthy donors. OS-derived exosomes were functionally evaluated in vivo and in vitro.

RESULTS

The characteristics of exosomes derived from OS patient serum and OS cell lines were confirmed by several methods. We found OS patients had a higher level of exosomal PD-L1 compared to healthy donors. Meanwhile, OS patients with pulmonary metastasis also showed a relatively higher level of exosomal PD-L1 than patients without metastasis. Next, bioinformatic analysis demonstrated that Sr-exosomes isolated from OS patients may involve in the important process of immune function and cancer pathogenesis for OS patients. Co-expression network centered with PD-L1 among Sr-exosomal differently expressed mRNA demonstrated exosomal N-cadherin had a close relationship with exosomal PD-L1 expression. Then, we confirmed higher level of Sr-exosomal N-cadherin in OS patients with pulmonary metastasis compared to ones without metastasis. Furthermore, we elucidated osteosarcoma-derived exosomes and exosomal-PD-L1 promoted the pulmonary metastasis in metastatic models. ROC (Receiver Operating Characteristic Curve) analysis showed AUC (Area Under Curve) of 0.823 for exosomal PD-L1, 0.806 for exosomal N-cadherin and 0.817 for exosomal N-cadherin/E-cadherin to distinguish OS patients with pulmonary metastasis from ones without metastasis.

CONCLUSIONS

Osteosarcoma stimulates pulmonary metastasis by releasing exosomes, that carry PD-L1 and N-cadherin. Detection of exosomal PD-L1 and N-cadherin from serum of OS patients may predict pulmonary metastasis progression for OS patients.

Association of Clinicopathological Features With Outcome in Chondrosarcomas of the Head and Neck

OBJECTIVE

The aim of this study is to assess the association between clinical and radiological features as well as of isocitrate dehydrogenase 1 and 2 (IDH 1,2) mutations with outcome in head and neck chondrosarcomas.

STUDY DESIGN

Retrospective study.

SETTING

Tertiary referral center.

METHODS

Clinical, histological, and molecular data of patients with head and neck chondrosarcomas treated by surgery were collected.

RESULTS

Forty-six patients were included. The mean age at diagnosis was 56 years (range, 17-78). The tumor originated from the skull base (52.2%), facial bones (28.2%), or laryngotracheal area (19.6%). At last follow-up (median 52.5 months), 38 patients were alive, 30 of which were disease free, whereas 8 had died, 4 of disease progression and 4 of other causes. Fourteen (30.4%) had local recurrence and 2 (4.3%) had lung metastasis. All cases were negative for cytokeratin AE1/AE3, brachyury, and IDH1 at immunohistochemistry, while Sanger sequencing identified IDH1/2 point mutations, typically IDH1 R132C, in 9 (37.5%) tumors arising from the skull base. Margin infiltration on the surgical specimen negatively affected the outcome, whereas no correlation was identified with IDH mutation status.

CONCLUSIONS

An adequate margin positively affects survival. IDH mutation status does not affect patient outcome.

Rational drug design, synthesis, and biological evaluation of novel chiral tetrahydronaphthalene-fused spirooxindole as MDM2-CDK4 dual inhibitor against glioblastoma

Simultaneous inhibition of MDM2 and CDK4 may be an effective treatment against glioblastoma. A collection of chiral spirocyclic tetrahydronaphthalene (THN)-oxindole hybrids for this purpose have been developed. Appropriate stereochemistry in THN-fused spirooxindole compounds is key to their inhibitory activity: selectivity differed by over 40-fold between the least and most potent stereoisomers in time-resolved FRET and KINOMEscan® in vitro assays. Studies in glioblastoma cell lines showed that the most active compound ent-4g induced apoptosis and cell cycle arrest by interfering with MDM2 -P53 interaction and CDK4 activation. Cells treated with ent-4g showed up-regulation of proteins involved in P53 and cell cycle pathways. The compound showed good anti-tumor efficacy against glioblastoma xenografts in mice. These results suggested that rational design, asymmetric synthesis and biological evaluation of novel tetrahydronaphthalene fused spirooxindoles could generate promising MDM2-CDK4 dual inhibitors in glioblastoma therapy.

Chondromesenchymal hamartomas in a 24-year-old male mimicking a posterior mediastinal tumor and a 5-month-old boy with postoperative disseminated intravascular coagulation: two case reports

BACKGROUND

Chondromesenchymal hamartoma of the chest wall is a rare, benign disease that usually presents at birth or in early infancy. It typically involves one or more ribs, forming a unilateral or bilateral extrapleural mass. Patients may be asymptomatic or complain of mild respiratory distress depending on tumor size and location. To the best of our knowledge, only two of the approximately 100 cases reported so far are adults.

CASE PRESENTATION

We present two cases of chondromesenchymal hamartoma. The first case involved the left fifth rib in a 24-year-old male, in close proximity to the fifth vertebral body in the left posterior mediastinum, mimicking a posterior mediastinal tumor on imaging. The tumor was excised via thoracoscopy and the patient had an uneventful postoperative course. The second case was that of a 5-month-old boy, who had a tumor involving the left fifth and sixth ribs which caused thoracic cage collapse. Following en bloc resection of the tumor and the involved rib segments, the patient was transferred to the intensive care unit for treatment of pulmonary infection and disseminated intravascular coagulation (DIC). He was discharged from the hospital in stable condition 11 days later. On histopathology, the tumor was found to be a chondromesenchymal hamartoma with immature spindle-shaped mesenchymal cells, plate-like hyaline cartilage, areas of woven bone formation, endochondral ossification and calcification, osteoclastic giant cells, and secondary aneurysmal bone cysts.

CONCLUSIONS

Although the presently reported cases have morphological characteristics similar to previously reported ones, they had distinct radiological and clinical characteristics. Patient 1 is only the third report of an adult with chondromesenchymal hamartoma. His case was characterized by its radiological appearance mimicking a posterior mediastinal tumor. Patient 2 represents the first documentation of DIC as a postoperative complication following excision of a chondromesenchymal hamartoma. We present these two cases to provide clinicopathological insights regarding this extremely rare tumor that are relevant to both pathologists and clinicians.

[Osteoid-forming bone tumors : Morphology and current translational cell biology]

Osteoid osteoma and osteoblastoma are the most important benign osteoid-forming tumors. They grow slowly and are well differentiated. Histologically, the tumor cells show no atypia and no increased mitoses. In typical cases, they can be clearly diagnosed. However, the rare cases on the dividing line between osteoblastoma and osteosarcoma are extremely problematic. In these cases, molecular genetic investigations should contribute to finding the correct diagnosis in the future.Juvenile highly malignant osteosarcoma is the most important malignant osteoid-forming tumor. About 40 years ago, neoadjuvant chemotherapy was introduced for the mostly young patients. This therapy highly significantly improved prognosis. However, a plateau phase was quickly reached and the last several decades have seen no further progress in conventional therapeutic approaches. There is no doubt that further progress can only be achieved on the basis of new molecular genetic and cell biological findings. The target-therapeutic strategies derived from these findings will be discussed in this review.The rare parosteal osteosarcoma and the even rarer periosteal osteosarcoma are mostly not highly malignant tumors that are located on the surface of bone. The parosteal osteosarcoma is usually G1 and the periosteal osteosarcoma G2. Occasionally, the differential diagnosis between a parosteal osteosarcoma and a fibrous dysplasia is difficult. In such rare cases, the detection of GNAS mutations in fibrous dysplasia can prove useful. In contrast to chondromas and chondrosarcomas, periosteal osteosarcomas do not contain IDH1 and IDH2 mutations.

Histological and molecular features of solitary fibrous tumor of the extremities: clinical correlation

Solitary fibrous tumor is a rare mesenchymal neoplasm that exhibits a broad spectrum of biological behaviors. Few studies relative to clinical-pathologic features and predictive factors have been reported, all involving a mixed population of tumors occurring at different anatomic sites. In this study, we described a cohort of 41 patients with solitary fibrous tumor of the extremities and evaluated the prognostic role of clinical and histological features, presence of C228T and C250T mutations at the TERT promoter region, and NAB2-STAT6 fusion variants. Patients were stratified according to the latest risk stratification model proposed by Demicco. The two patients with metastasis at presentation were in the high-risk group; the one with metastasis after surgery was classified in the intermediate-risk group. TERT promoter mutations were detected in 9 out of 38 DNA available. All patients with metastasis were characterized by a TERT promoter mutation. TERT promoter mutation was associated with mitoses > 4 per high-power field (p = 0.001), necrosis (p = 0.049), and size > 10 cm (p = 0.031). NAB2-STAT6 fusion variants were detected in 27 out of 41 cases without any prognostic value. In conclusion, we confirmed that the patients with solitary fibrous tumor of the limbs have a better prognosis than other solitary fibrous tumors, with a very low percentage of metastatic events. Besides, our data support an association between TERT promoter mutations and histologically malignant features, suggesting a possible molecular role in stratifying patients into intermediate- to high-risk tumor.

Future directions in soft tissue sarcoma treatment

Sarcoma is a broad term for mesenchymal malignancies that arise from soft tissue or bone. Despite classification by histologic subtype, clinical behavior and response to therapy have great variability. Modern genetic sequencing techniques have been able to identify additional genetic variability and subsequently new targeted therapies. In this review, we discuss the current state of STS diagnostics and treatment and explore some of the more promising areas in which progress is being made. We discuss therapies targeting PDGFRα/KIT, β-Catenin/APC/NOTCH, IDH-1/2 mutations, MDM2 amplifications, EZH2/INI1 expression loss, ALK fusion, and ASPSCR1-TFE3 fusion. We also discuss the progress that has been made within immunotherapies. While soft tissue sarcomas still portend a poor prognosis, these targeted therapies and immunotherapies provide treatment with less toxic side effects.

Unlocking bone for proteomic analysis and FISH

Bone tissue is critically lagging behind soft tissues and biofluids in our effort to advance precision medicine. The main challenges have been accessibility and the requirement for deleterious decalcification processes that impact the fidelity of diagnostic histomorphology and hinder downstream analyses such as fluorescence in-situ hybridization (FISH). We have developed an alternative fixation chemistry that simultaneously fixes and decalcifies bone tissue. We compared tissue morphology, immunohistochemistry (IHC), cell signal phosphoprotein analysis, and FISH in 50 patient matched primary bone cancer cases that were either formalin fixed and decalcified, or theralin fixed with and without decalcification. Use of theralin improved tissue histomorphology, whereas overall IHC was comparable to formalin fixed, decalcified samples. Theralin-fixed samples showed a significant increase in protein and DNA extractability, supporting technologies such as laser-capture microdissection and reverse phase protein microarrays. Formalin-fixed bone samples suffered from a fixation artifact where protein quantification of β-actin directly correlated with fixation time. Theralin-fixed samples were not affected by this artifact. Moreover, theralin fixation enabled standard FISH staining in bone cancer samples, whereas no FISH staining was observed in formalin-fixed samples. We conclude that the use of theralin fixation unlocks the molecular archive within bone tissue allowing bone to enter the standard tissue analysis pipeline. This will have significant implications for bone cancer patients, in whom personalized medicine has yet to be implemented.

Clinical genomic profiling to identify actionable alterations for investigational therapies in patients with diverse sarcomas

Background

There are currently no United States Food and Drug Administration approved molecularly matched therapies for sarcomas except gastrointestinal stromal tumors. Complicating this is the extreme diversity, heterogeneity, and rarity of these neoplasms. Few therapeutic options exist for relapsed and refractory sarcomas. In clinical practice many oncologists refer patients for genomic profiling hoping for guidance on treatment options after standard therapy. However, a systematic analysis of actionable mutations has yet to be completed. We analyzed genomic profiling results in patients referred to MD Anderson Cancer Center with advanced sarcomas to elucidate the frequency of potentially actionable genomic alterations in this population.

Methods

We reviewed charts of patients with advanced sarcoma who were referred to investigational cancer therapeutics department and had CLIA certified comprehensive genomic profiling (CGP) of 236 or 315 cancer genes in at least 50ng of DNA. Actionable alterations were defined as those identifying anti-cancer drugs on the market, in registered clinical trials, or in the Drug-Gene Interaction Database.

Results

Among the 102 patients analyzed median age was 45.5 years (range 8-76), M: F ratio 48:54. The most common subtypes seen in our study were leiomyosarcoma (18.6%), dedifferentiated liposarcoma (11%), osteosarcoma (11%), well-differentiated liposarcoma (7%), carcinosarcoma (6%), and rhabdomyosarcoma (6%). Ninety-five out of 102 patients (93%) had at least one genomic alteration identified with a mean of six mutations per patient. Of the 95 biopsy samples with identifiable genomic alterations, the most commonly affected genes were TP53 (31.4%), CDK4 (23.5%), MDM2 (21.6%), RB1 (18.6%), and CDKN2A/B (13.7%). Notable co-segregating amplifications included MDM2-CDK4 and FRS2-FGF. Sixteen percent of patients received targeted therapy based on CGP of which 50% had at least stable disease.

Conclusions

Incorporating CGP into sarcoma management may allow for more precise diagnosis and sub-classification of this diverse and rare disease, as well as personalized matching of patients to targeted therapies such as those available in basket clinical trials.

Development of high-grade osteosarcoma in a patient with recurrent giant cell tumor of the ischium while receiving treatment with denosumab

Malignant transformation of giant cell tumor of bone (GCTB) without radiotherapy exposure is exceptionally rare, occurring in less than 1% of GCTBs. The safety and efficacy of denosumab in patients with GCTB was recently reported. We herein report a case of a benign recurrent GCTB with an H3F3A mutation that underwent secondary malignant transformation during treatment with denosumab. A 29-year-old woman underwent curettage of a GCTB of the left ischium in 2005. Ten years after the first surgery, the GCTB recurred locally. We started treatment with denosumab. During the first 5 months of treatment, we observed a demarcated area of osteosclerosis in the recurrent lesion, and the patient's clinical condition improved. At 6 months, however, the patient developed pain, and a rapidly growing mass was detected by computed tomography. An incisional biopsy was performed. Histologic analysis showed a high-grade osteosarcoma. The patient developed lung metastases and died soon after beginning chemotherapy. The mechanism of sarcomatous transformation of GCTB during denosumab therapy is unclear. These findings suggest that the scientific community should be aware of the possible malignant transformation of GCTB during denosumab treatment.

[Protocol for the study of bone tumours and standardization of pathology reports]

Primary bone neoplasms represent a rare and heterogeneous group of mesenchymal tumours. The prevalence of benign and malignant tumours varies; the latter (sarcomas) account for less than 0.2% of all malignant tumours. Primary bone neoplasms are usually diagnosed and classified according to the criteria established and published by the World Health Organization (WHO 2013). These criteria are a result of advances in molecular pathology, which complements the histopathological diagnosis. Bone tumours should be diagnosed and treated in referral centers by a multidisciplinary team including pathologists, radiologists, orthopedic surgeons and oncologists. We analyzed different national and international protocols in order to provide a guide of recommendations for the improvement of pathological evaluation and management of bone tumours. We include specific recommendations for the pre-analytical, analytical, and post-analytical phases, as well as protocols for gross and microscopic pathology.

GNAS mutations are not detected in parosteal and low-grade central osteosarcomas

Parosteal osteosarcoma, low-grade central osteosarcoma, and fibrous dysplasia share similar histological features that may pose a diagnostic challenge. The detection of GNAS mutations in primary bone tumors has been useful in clinical practice for diagnosing fibrous dysplasia. However, the recent report of GNAS mutations being detected in a significant proportion of parosteal osteosarcoma challenges the specificity of this mutation. As the number of cases reported in this study was small we set out to determine if these results could be reproduced. We studied 97 formalin-fixed paraffin-embedded low-grade osteosarcomas from 90 patients including 62 parosteal osteosarcomas, of which MDM2 amplification was detected in 79%, 11 periosteal osteosarcomas and 24 low-grade central osteosarcoma samples. The mutational status of GNAS was analyzed in codons p.R201, p.Q227, and other less common GNAS alterations by bidirectional Sanger sequencing and/or next generation sequencing using the Life Technologies Ion Torrent platform. GNAS mutations were not detected in any of the low-grade osteosarcomas from which informative DNA was extracted. Our findings therefore support prior observations that GNAS mutations are highly specific for fibrous dysplasia and occur rarely, if ever, in parosteal and other low-grade osteosarcomas.