Soft Tissue Sarcoma
Soft tissue sarcomas span many histological subtypes whose natural history and treatment sensitivity differ considerably, which makes precise subtyping consequential rather than academic.
Disease categories
Major disease categories
- Liposarcoma
- Leiomyosarcoma
- Undifferentiated pleomorphic sarcoma
- Synovial sarcoma
- Myxofibrosarcoma
- Angiosarcoma
- Desmoid tumours
Molecular
Molecular considerations
Translocation-associated sarcomas carry defining fusions. MDM2 and CDK4 amplification identifies well-differentiated and dedifferentiated liposarcoma. CTNNB1 alterations characterise desmoid tumours.
Markers commonly discussed in soft tissue sarcoma
- SS18 rearrangement
- MDM2 / CDK4
- CTNNB1
- FUS-DDIT3
- NTRK fusions
Not exhaustive, and not every marker is assessed in every patient. Which of these is relevant depends on the individual case and should be discussed with the treating team.
Testing
Genomic testing considerations
Fusion-capable testing where the subtype requires it.
Germline
Germline considerations
Considered in young patients and where family history is suggestive.
Molecular monitoring
ctDNA and liquid biopsy considerations
Investigational.
Single-cell & computation
Single-cell and algorithmic approaches
Single-cell analysis in sarcoma is used to characterise differentiation state and the stromal and immune compartments, both of which vary widely across a group of more than a hundred entities. Single-cell DNA sequencing contributes to clonal structure questions in tumours that are frequently heterogeneous. Algorithm work centres on fusion detection and breakpoint characterisation — the defining event in many sarcoma subtypes — together with methylation-based classification for diagnostically difficult cases.
Decisions
Treatment decision questions
Questions worth raising with a treating team when a decision is being made:
- Is the subtype confirmed, ideally at a specialist centre?
- Has fusion or amplification testing been performed where relevant?
Resistance
Resistance and recurrence questions
- Has the diagnosis been reconsidered where behaviour is atypical?
Trials
Clinical trial considerations
Subtype-specific trials predominate.
When a precision oncology review may help
A review is most useful where the standard pathway has been exhausted or where the picture is more complicated than a protocol accounts for — rare presentations, treatment resistance, complex or apparently contradictory molecular findings, or a decision between several defensible options.
The output is a structured analysis and a set of questions for the treating team. It is not treatment, and it does not replace the treating oncologist.