Simple and aneurysmal bone cysts are benign lytic bone lesions, usually encountered in children and adolescents. Simple bone cyst is a cystic, fluid-filled lesion, which may be unicameral (UBC) or partially separated. UBC can involve all bones, but usually the long bone metaphysis and otherwise primarily the proximal humerus and proximal femur. The classic aneurysmal bone cyst (ABC) is an expansive and hemorrhagic tumor, usually showing characteristic translocation. About 30% of ABCs are secondary, without translocation; they occur in reaction to another, usually benign, bone lesion. ABCs are metaphyseal, excentric, bulging, fluid-filled and multicameral, and may develop in all bones of the skeleton. On MRI, the fluid level is evocative. It is mandatory to distinguish ABC from UBC, as prognosis and treatment are different. UBCs resolve spontaneously between adolescence and adulthood; the main concern is the risk of pathologic fracture. Treatment in non-threatening forms consists in intracystic injection of methylprednisolone. When there is a risk of fracture, especially of the femoral neck, surgery with curettage, filling with bone substitute or graft and osteosynthesis may be required. ABCs are potentially more aggressive, with a risk of bone destruction. Diagnosis must systematically be confirmed by biopsy, identifying soft-tissue parts, as telangiectatic sarcoma can mimic ABC. Intra-lesional sclerotherapy with alcohol is an effective treatment. In spinal ABC and in aggressive lesions with a risk of fracture, surgical treatment should be preferred, possibly after preoperative embolization. The risk of malignant transformation is very low, except in case of radiation therapy.

Rhabdomyosarcomas with TFCP2 fusions represent an emerging subtype of tumors, initially discovered by RNA-sequencing. We report herein the clinicopathological, transcriptional and genomic features of a series of 14 cases.Cases were retrospectively and prospectively recruited and studied by immunohistochemistry (MYF4, MYOD1, S100, AE1/E3, ALK), fluorescence in situ hybridization with TFCP2 break-apart probe (n=10/14), array-comparative genomic hybridization (Agilent), whole RNA-sequencing (Truseq Exome, Illumina) or anchored multiplex PCR based targeted next-generation sequencing (Archer® FusionPlex® Sarcoma kit). Patient's age ranged between 11 to 86 years, including 5 pediatric cases. Tumors were located in bone (n=12/14) and soft tissue (n=2/14). Most bone tumors invaded surrounding soft tissue. Craniofacial bones were over-represented (n=8/12). Median survival was 8 months and 5 patients are currently alive with a median follow-up of 20 months. Most tumors displayed a mixed spindle cell and epithelioid pattern with frequent vesicular nuclei. All tumors expressed keratins and showed a rhabdomyogenic phenotype (defined as expression of MYF4 and/or MYOD1). ALK was overexpressed in all but 3 cases without underlying ALK fusion on break-apart FISH (n=5) nor next generation sequencing (n=14).TFCP2 was fused in 5' either to EWSR1 (n=6) or FUS (n=8). EWSR1 was involved in both soft tissue cases. FISH with TFCP2 break-apart probe was positive in all tested cases (n=8), including one case with unbalanced signal. On array-CGH, all tested tumors displayed complex genetic profiles with genomic indexes ranging from 12.8 to 90 and CDKN2A deletion was recurrent (n=9/10). FET-TFCP2 rhabdomyosarcomas clustered together and distinctly from other rhabdomyosarcomas subgroups.Altogether, our data confirm and expand the spectrum of the new family of FET-TFCP2 rhabdomyosarcomas which are associated with a predilection for the craniofacial bones, an aggressive course and recurrent pathological features. Their association with ALK overexpression might represent a therapeutic vulnerability.

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The French phase 3 trial (OS 2006) testing zoledronic acid, an osteoclast inhibitor, with chemotherapy and surgery did not improve the outcome of patients with osteosarcoma (OS). To understand this unexpected result, the presence of infiltrating immune cells was investigated in 124 pre-therapeutic biopsies of patients enrolled in the trial. The percentage of CD68/CD163 tumor-infiltrating macrophages (TAMs), CD8 lymphocytes, osteoclasts, and the PD1/PDL-1 checkpoint were assessed by immunohistochemistry. M1/M2 macrophage polarization was characterized by pSTAT1/CMAF staining. The expression of these biomarkers was correlated with clinical outcome. No statistical correlations were found with response to chemotherapy. High CD163 levels (>50% of cells per core; 43.8% of patients) were associated with CMAF nuclear expression and significantly correlated with better overall survival ( = 0.0025) and longer metastasis progression-free survival (MPFS, = 0.0315) independently of metastatic status ( = 0.002). Only a trend was observed for patients with high CD68-positive cells ( = 0.0582). CD8 staining was positive in >50% of cases with a median staining of 1%. Lower CD8 levels were associated with metastatic disease at diagnosis and the presence of CD8-positive cells significantly correlated with improved overall survival in zoledronate-treated patients ( = 0.0415). PD1/PDL-1 staining was negative in >80% of cases and was not correlated with outcome. Finally, CD163-positive TAMs and CD8 positive cells are crucial prognostic biomarkers in OS, whereas PD1/PDL-1 checkpoint plays a minor role. For the first time, we described a correlation between CD8 positive cells and survival in zoledronate-treated patients. The immunohistochemical analysis of the microenvironment in biopsies may represent a novel tool for therapeutic stratification.

Low-grade osteosarcoma is a rare malignancy that may be subdivided into two main subgroups on the basis of location in relation to the bone cortex, that is, parosteal osteosarcoma and low-grade central osteosarcoma. Their histological appearance is quite similar and characterized by spindle cell stroma with low-to-moderate cellularity and well-differentiated anastomosing bone trabeculae. Low-grade osteosarcomas have a simple genetic profile with supernumerary ring chromosomes comprising amplification of chromosome 12q13-15, including the cyclindependent kinase 4 (CDK4) and murine double-minute type 2 (MDM2) gene region. Low-grade osteosarcoma can be confused with fibrous and fibro-osseous lesions such as fibromatosis and fibrous dysplasia on radiological and histological findings. We investigated MDM2-CDK4 immunohistochemical expression in a series of 72 low-grade osteosarcomas and 107 fibrous or fibro-osseous lesions of the bone or paraosseous soft tissue. The MDM2-CDK4 amplification status of low-grade osteosarcoma was also evaluated by comparative genomic hybridization array in 18 cases, and the MDM2 amplification status was evaluated by fluorescence in situ hybridization or quantitative real-time polymerase chain reaction in 31 cases of benign fibrous and fibro-osseous lesions. MDM2-CDK4 immunostaining and MDM2 amplification by fluorescence in situ hybridization or quantitative real-time polymerase chain reaction were investigated in a control group of 23 cases of primary high-grade bone sarcoma, including 20 conventional high-grade osteosarcomas, two pleomorphic spindle cell sarcomas/malignant fibrous histiocytomas and one leiomyosarcoma. The results showed that MDM2 and/or CDK4 immunoreactivity was present in 89% of lowgrade osteosarcoma specimens. All benign fibrous and fibro-osseous lesions and the tumors of the control group were negative for MDM2 and CDK4. These results were consistent with the MDM2 and CDK4 amplification results. In conclusion, immunohistochemical expression of MDM2 and CDK4 is specific and provides sensitive markers for the diagnosis of low-grade osteosarcomas, helping to differentiate them from benign fibrous and fibro-osseous lesions, particularly in cases with atypical radio-clinical presentation and/or limited biopsy samples.

Various tumors metastasize via lymph vessels and lymph nodes to distant organs. Even though tumors are hypoxic, the mechanisms of how hypoxia regulates lymphangiogenesis remain poorly characterized. Here, we show that hypoxia reduced vascular endothelial growth factor C (VEGF-C) transcription and cap-dependent translation via the upregulation of hypophosphorylated 4E-binding protein 1 (4E-BP1). However, initiation of VEGF-C translation was induced by hypoxia through an internal ribosome entry site (IRES)-dependent mechanism. IRES-dependent VEGF-C translation was independent of hypoxia-inducible factor 1α (HIF-1α) signaling. Notably, the VEGF-C IRES activity was higher in metastasizing tumor cells in lymph nodes than in primary tumors, most likely because lymph vessels in these lymph nodes were severely hypoxic. Overall, this transcription-independent but translation-dependent upregulation of VEGF-C in hypoxia stimulates lymphangiogenesis in tumors and lymph nodes and may contribute to lymphatic metastasis.

This study suggests that bone oncogenesis driven by TP53 or RB1 mutations occurs on a background of relative genetic stability and that the dedifferentiated OS subtype represents a clinico-pathological entity with distinct oncogenic mechanisms and thus requires different therapeutic management.

This article has an accompanying continuing medical education activity, also eligible for MOC credit, on page e19. Learning Objective: Upon completion of this CME activity successful learners will be able to (1) evaluate the probability of a venous thromboembolism (VTE) in patients with newly diagnosed pancreatic ductal adenocarcinoma (PDAC); (2) identify the risk factors for VTE in patients with PDAC; and (3) assess the impact of VTE on survival in patients with PDAC. Venous Thromboembolism and Pancreatic CancerThe BACAP-VTE Study : pancreatic cancer patients prospectively followed-up from time of enrollment until last visit or death 152 patients (20.79%) developed a VTE during a median follow-up of 19.3 months Patients developing VTE during follow-up had lower PFS (HR 1.74, 95%CI 1.19-2.54, P=.004) Patients developing VTE during follow-up had lower OS (HR 2.02, 95%CI 1.57-2.60, P<.001).