round cell variant), tumor grading, tumor site and patients’ median age or gender. Solitary fibrous tumors (SFTs) showed TERT promoter mutations in four cases (4/31; 13%), which were exclusively located at position C228T. In addition, two malignant peripheral nerve sheath tumors (MPNSTs) harbored a TERT promoter mutation (2/35; 6%), one case with a C228T and the other one with a C250T mutation. Finally, a TERT promoter mutation at position C228T was found in one of the synovial sarcomas (SSs) examined (1/25; 4%).

All other sarcoma types, which comprised 61 dedifferentiated liposarcomas, 15 pleomorphic liposarcomas, 27 leiomyosarcomas, 40 undifferentiated pleomorphic sarcomas, 17 myxofibrosarcomas, Proteasome inhibitor 9 low-grade fibromyxoid sarcomas, 10 dermatofibrosarcomata

protuberans, 8 extraskeletal myxoid chondrosarcomas, 9 angiosarcomas, 6 alveolar soft part sarcomas, 5 clear ITF2357 cell sarcomas, and 4 epithelioid sarcomas had a wild type genotype at the two TERT promoter hotspot loci (Table 1). Table 1 Prevalence of TERT promoter hotspot mutations in soft tissue tumors Diagnosis Mut (n) Total (n) Mut (%) C228T (n) C250T (n) Myxoid liposarcoma 29 39 74% 28 1 Dedifferentiated liposarcoma 0 61       Pleomorphic liposarcoma 0 15       Leiomyosarcoma 0 27       Synovial sarcoma 1 25 4%   1 Malignant peripheral nerve sheath tumor 2 35 6% 1 1 Undifferentiated pleomorphic sarcoma 0 40       Myxofibrosarcoma 0 17       Low grade fibromyxoid sarcoma 0 9       Dermatofibrosarcoma protuberans 0 10       Solitary fibrous tumor 4 31 13% 4   Extraskeletal myxoid chondrosarcoma 0 8       Angiosarcoma 0 9       Alveolar soft part tumor 0 6       Clear cell sarcoma 0 5       Epithelioid sarcoma 0 4         36 341   33 much 3 Figure 1 Schematic figure of the TERT promoter region. Schematic figure of the TERT promoter region with nucleotide numbering of the molecular

position on chromosome 5, DNA sequence of the mutational hotspot region with a wild type strand and a mutated strand, which shows the nucleotide exchange of cytosine by thymine (depicted in red). Each mutation leads to a new binding motif for E-twenty six/ternary complex factors (Ets/TCF) transcription factors (highlighted by greyish rectangles). Representative sequencing chromatograms show heterozygous C228T/C250T mutations (indicated by arrows). Table 2 Correlation between clinicopathological patient characteristics and TERT promoter genotype in myxoid liposarcomas   Mutant VX-689 cell line Wild-type Pvalue Phenotype (n = 39)     0.2125   Myxoid 23 6     Round cell 6 4   Grading (n = 39)     0.6034   G1 3 1     G2 22 6     G3 4 3   Localization (n = 39)     0.1958   Extremity 23 10     Other 5 0   Age (years) (n = 39)     0.6748   Mean ± SD 48 ± 3 50 ± 5     Median (range) 46 (16–84) 43 (36–74)   Gender (n = 39)     0.6395   Female 9 3     Male 20 7   TERT promoter hotspot mutations in soft tissue sarcoma cell lines We also sequenced 16 sarcoma cell lines for the TERT promoter hotspot mutations (Table 3).