The optimal management of rare tumours (i.e. from accurate diagnosis to management in reference centres) is a public health challenge. In 2009, the French National Cancer Institute (INCa) identified and financially supported the two expert networks for pathological and clinical diagnosis and management of soft tissue tumours. The activities of both networks were prospectively collected using a nationwide database (rreps.org). Data describing the diagnosis management of 863 successive cases of desmoids tumours (DT) were prospectively collected from 2010 to 2013 and analysed. The number of confirmed DT constantly improved from January 2010 to December 2013 (from 173 to 273 cases per year); the expected incidence ranged from 132 to 330 cases/year. The rate of cases diagnosed with core-needle biopsies and CTNNB1 mutational status analysis increased from 30.6 to 40.7% and from 87.8 to 94.1%, respectively. The mean delay for pathological diagnosis confirmation constantly decreased from 107 to 47 d. Among the 846 adult patients, 414 (48.9%) patients were treated by reference centres. The rate of patients managed by reference centres constantly increased with time from 36.9 to 49.5% since 2010. The median management time of the referral centres constantly decreased from 440 to 67 d. The two expert networks worked synergistically and improved diagnosis modalities of rare desmoid tumours at a national level. The impact of management by expert networks on the outcome will be prospectively analysed in the future.

Biphenotypic sinonasal sarcoma (BSNS) is a locally aggressive tumor occurring in the sinonasal region. It harbors both myogenic and neural differentiation and is characterized by PAX3 rearrangement with MAML3 as the most frequent fusion partner, but the partner of PAX3 remains unidentified in a subset of cases. About 70 cases have been reported so far. In this study, we report a series of 41 cases with clinical, pathologic, and molecular description. Twenty-five (61%) patients were female individuals, and the median age was 49 years. Tumors arose predominantly in the nasal cavity and ethmoidal sinuses. Local recurrences occurred in 8 cases of the 25 (32%). Histologic features were characteristic of BSNS, with 5 cases showing focal rhabdomyoblastic differentiation. Immunohistochemistry showed a constant positivity of S100 protein and PAX3 and negativity of SOX10. MyoD1 was focally positive in 91% of cases, whereas only 20% were positive for myogenin. Molecular analysis showed a PAX3-MAML3 transcript in 37 cases (90%). RNA sequencing was performed in the 4 negative cases for PAX3-MAML3 fusion, and it showed that 1 case harbored a PAX3-FOXO1 fusion, as previously described in the literature, and 2 novel fusions: PAX3-WWTR1 fusion in 2 cases and PAX3-NCOA2 fusion in 1 case. RNA sequencing results were confirmed by fluorescence in situ hybridization, reverse transcription-polymerase chain reaction, and Sanger sequencing. The PAX3-NCOA2-positive case showed focal rhabdomyoblastic differentiation. In conclusion, we report 2 novel fusions (PAX3-WWTR1 and PAX3-NCOA2) in BSNS and show that MyoD1 is more sensitive than myogenin for demonstrating myogenic differentiation in this tumor.

The long term outcome of advanced sarcoma patients treated with trabectedin outside of clinical trials and the utility of maintenance treatment has not been reported.

Solitary Fibrous Tumours (SFT) and haemangiopericytomas (HPC) are rare meningeal tumours that have to be distinguished from meningiomas and more rarely from synovial sarcomas. We recently found that ALDH1A1 was overexpressed in SFT and HPC as compared to soft tissue sarcomas. Using whole-genome DNA microarrays, we defined the gene expression profiles of 16 SFT/HPC (9 HPC and 7 SFT). Expression profiles were compared to publicly available expression profiles of additional SFT or HPC, meningiomas and synovial sarcomas. We also performed an immunohistochemical (IHC) study with anti-ALDH1 and anti-CD34 antibodies on Tissue Micro-Arrays including 38 SFT (25 meningeal and 13 extrameningeal), 55 meningeal haemangiopericytomas (24 grade II, 31 grade III), 163 meningiomas (86 grade I, 62 grade II, 15 grade III) and 98 genetically confirmed synovial sarcomas. ALDH1A1 gene was overexpressed in SFT/HPC, as compared to meningiomas and synovial sarcomas. These findings were confirmed at the protein level. 84% of the SFT and 85.4% of the HPC were positive with anti-ALDH1 antibody, while only 7.1% of synovial sarcomas and 1.2% of meningiomas showed consistent expression. Positivity was usually more diffuse in SFT/HPC compared to other tumours with more than 50% of tumour cells immunostained in 32% of SFT and 50.8% of HPC. ALDH1 was a sensitive and specific marker for the diagnosis of SFT (SE = 84%, SP = 98.8%) and HPC (SE = 84.5%, SP = 98.7%) of the meninges. In association with CD34, ALDH1 expression had a specificity and positive predictive value of 100%. We show that ALDH1, a stem cell marker, is an accurate diagnostic marker for SFT and HPC, which improves the diagnostic value of CD34. ALDH1 could also be a new therapeutic target for these tumours which are not sensitive to conventional chemotherapy.