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Ancillary molecular analysis in the diagnosis of soft tissue tumours: reassessment of its utility at a specialist centre
  1. Katherine Vroobel1,
  2. David Gonzalez2,
  3. Dorte Wren2,
  4. Lisa Thompson2,
  5. John Swansbury3,
  6. Cyril Fisher1,
  7. Khin Thway1
  1. 1Sarcoma Unit, Royal Marsden Hospital, London, UK
  2. 2Department of Molecular Diagnostics, Royal Marsden Hospital, Sutton, Surrey, UK
  3. 3Department of Clinical Cytogenetics, Royal Marsden Hospital, Sutton, Surrey, UK
  1. Correspondence to Dr Khin Thway, Sarcoma Unit, The Royal Marsden NHS Foundation Trust, 203 Fulham Road, London SW3 6JJ, UK; khin.thway{at}rmh.nhs.uk

Abstract

Aims The histological diagnosis of soft tissue tumours (STTs) can be difficult, sometimes requiring a combination of morphology, immunophenotype and ancillary molecular tests. Many STTs are associated with characteristic genetic aberrations that can be assessed using fluorescence in situ hybridisation (FISH), reverse transcription-PCR (RT-PCR) or mutational analysis. We have previously assessed the practicality and sensitivity of using these modalities as part of the routine diagnosis of STT in paraffin-embedded material and now revisit the subject in light of further experience in this field.

Methods 200 consecutive cases from 2013 that had undergone FISH, RT-PCR or mutational analysis were assessed to evaluate their diagnostic utility compared with preliminary histological assessment.

Results 218 FISH, 91 RT-PCR and 43 mutational analysis tests were performed. Compared with the previous study, FISH for MDM2 amplification in possible well-differentiated/dedifferentiated liposarcomas, and mutational analysis for assessing KIT, PDGFR and BRAF mutations made up a large proportion of the workload (107 and 43 tests, respectively). As in the previous study, alveolar rhabdomyosarcoma showed the best FISH:RT-PCR concordance. Unlike previously, RT-PCR showed marginally higher sensitivity than FISH (78.9% and 76.9%), while continuing to demonstrate higher specificity (90.9% and 84.3%). RT-PCR again showed an increased failure rate (5.5%; 1% for FISH).

Conclusions We demonstrate the continuing utility of RT-PCR and FISH for STT diagnosis, and that each has advantages in specific contexts. These ancillary molecular tests are important tools in both defining and excluding diagnoses of STT, which is crucial in determining prognosis and guiding appropriate management.

  • SOFT TISSUE
  • SOFT TISSUE TUMOURS
  • MOLECULAR PATHOLOGY
  • FISH

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