Case 8
An 18-year-old male presented with pain, weight loss and fever. Biopsy of the tumour mass and histopathological assessment revealed a spindle cell sarcoma.
NTRK gene fusion testing
IHC with a PAN-NTRK antibody revealed high positivity.
TRK inhibitor treatment
The patient was treated with a TRK inhibitor (larotrectinib) and responded within 2 months.
Response to treatment enabled surgery to remove residual disease 2 months later (i.e., 4 months from baseline).
Nine months after surgery however the patients developed local and metastatic relapse and was rechallenged with larotrectinib to which he responded 6 months later and continues to respond to date (July 2022).
Clinical interpretation and impact of NTRK gene fusion testing
NTRK-rearranged spindle cell tumours encompass a histologically diverse spectrum spanning low and high cellularity and represent an emerging group of molecularly defined rare sarcoma still under refinement. They do express high levels of NTRK proteins and hence IHC provides a suitable diagnostic method.
References
- Suurmeijer AJ, Dickson BC, Swanson D et al. The histologic spectrum of soft tissue spindle cell tumors with NTRK3 gene rearrangements. Genes Chromosomes Cancer. 2019; 58(11):739-746.