Methods :
Three pediatric extrapulmonary spindle cell sarcomas with primitive morphology and rhabdomyosarcomatous differentiation which raised suspicion for association with DICER1 pathogenic variation were studied. The cases were enrolled in the International Pleuropulmonary Blastoma / (PPB) / DICER1 Registry. Institutional review board approval was sought (EC/WV/TMC/41/20). Tumour sequencing was done at Heidelberg Institute, on Illumina NextSeq platform for 130 brain tumour related genes applying panel NPHD2015A, enriched with Agilent SureSelect method for 1 case. This was followed by confirmation of germline alteration using Sanger sequencing. DNA methylation profiling was also done with Illumina Human Methylation 850 (850k) array and internal classified V11b4 and sarcoma_v6.3. For other two cases sequencing was performed using the Ion Torrent Personal Genome Machine (PGM) for coding regions of DICER1 , p53 and a single amplicon of FOXL2, at ResourcePath, through the International PPB/DICER1 Registry and Children’s Minnesota, Minneapolis, MN.
All immunohistochemical studies on the cases were done in-house, on the Leica Bondmax. Fluorescent in-situ hybridization (FISH) evaluation for chromosome 8 using MYC/CEN-8 dual colour probe (Zytovision GmbH, Germany) was performed in 2 cases.
Clinical details were retrieved from the hospital electronic medical records.