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12.1 What are the main types of genetic alterations that are found in mesenchymal tumours?
Chromosomal translocations that generate a chimeric fusion transcript; copy number change (gene amplifications); point mutations and complex genomic events.
12.2. Is the presence of EWSR1 gene rearrangement specific of Ewing’s sarcoma?
No. EWSR1 gene rearrangement is involved in a variety of sarcoma subtypes, including Ewing’s sarcoma.
12.3 What type of FISH probe should be used to detect gene rearrangements on unbalanced translocations?
Fusion probes. Break-apart probes should be avoided as they would reveal a normal signal (fused –yellow) and a single red or green signal, which would be non-conclusive.
12.4 How can you safely differentiate a large lipoma from an atypical lipomatous tumour?
The presence of MDM2 gene amplification in a well-differentiated lipomatous tumo
12.5 Gastro-intestinal stromal tumour has specific mutations that can be therapeutically targeted. Check if you know the main genes involved.
KIT and PDGFR alpha