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Surgical resection and targeted therapy in a pediatric NTRK-rearranged low-grade spindle cell sarcoma: a case report
Chien-Kai Wang1,2, Yen-Lin Liu3,4,5, Wan-Ling Ho3,4,5
1Department of Neurosurgery, Taipei Medical University Hospital, Taipei Medical University, Taipei, Taiwan.
Background:
Neurotrophic tropomyosin receptor kinase (NTRK) gene fusions have emerged as important oncogenic drivers across a wide range of malignancies, including soft tissue sarcomas. Early detection of these fusions facilitates precision treatment with TRK inhibitors, significantly improving clinical outcomes. However, diagnosing NTRK-rearranged spindle cell neoplasms (NTRK-RSCNs) remains challenging due to their histological heterogeneity and overlap with other soft tissue tumors.
Case Presentation:
We present the case of an 8-year-old boy with a history of infantile fibromatosis, who developed progressive right ankle dorsiflexion weakness and right foot drop. Magnetic resonance imaging revealed a large, homogeneously enhancing soft tissue mass with extensive perineural involvement and spinal cord compression spread from T8 to L3 levels. The patient underwent T10-L1 laminectomy and partial tumor resection under intraoperative neurophysiological monitoring.
Diagnosis, Treatment, And Outcome:
Histopathological analysis identified a low-grade spindle cell neoplasm with focal positivity for S100 and CD34, and patchy pan-tropomyosin receptor kinase (TRK) expression. Molecular studies using fluorescence in situ hybridization and RNA-based next-generation sequencing confirmed a TPM3-NTRK1 fusion, establishing the diagnosis of NTRK-rearranged low-grade spindle cell sarcoma. Postoperatively, targeted therapy with a TRK inhibitor Larotrectinib (100 mg/m2/dose twice daily) was initiated. Over a 2-year follow-up period, the patient demonstrated significant neurological improvement and stable disease without evidence of progression on serial imaging studies.
Conclusion:
This case underscores the importance of integrating molecular diagnostics into the evaluation of atypical spindle cell tumors, particularly those presenting with aggressive clinical features despite low-grade histology. Early identification of NTRK fusions enables timely initiation of TRK inhibitor therapy, offering durable disease control and functional recovery. Broader awareness and implementation of molecular testing can greatly enhance the management of rare pediatric sarcomas.
Insights
Neurotrophic tropomyosin receptor kinase (NTRK) gene fusions drive rare pediatric sarcomas. Early molecular diagnosis of NTRK fusions enables effective TRK inhibitor therapy, leading to improved outcomes and disease control.
Area of Science:
- Oncology
- Molecular Diagnostics
- Pediatric Sarcoma Research
Background:
- Neurotrophic tropomyosin receptor kinase (NTRK) gene fusions are key drivers in various cancers, including soft tissue sarcomas.
- Accurate diagnosis of NTRK-rearranged spindle cell neoplasms (NTRK-RSCNs) is difficult due to histological variability.
Purpose of the Study:
- To highlight the diagnostic and therapeutic implications of NTRK gene fusions in a pediatric soft tissue sarcoma case.
- To emphasize the role of molecular diagnostics in guiding targeted therapy for rare sarcomas.
Main Methods:
- Case presentation of an 8-year-old boy with a large soft tissue mass.
- Histopathological and molecular analyses (FISH, RNA-NGS) to identify TPM3-NTRK1 fusion.
- Surgical resection followed by targeted therapy with Larotrectinib.
Main Results:
- Diagnosis of NTRK-rearranged low-grade spindle cell sarcoma confirmed by molecular testing.
- Patient showed significant neurological improvement and stable disease on TRK inhibitor therapy over 2 years.
- Successful management of a rare pediatric sarcoma through integrated diagnostics and targeted treatment.
Conclusions:
- Molecular diagnostics are crucial for evaluating spindle cell tumors with aggressive features.
- Early identification of NTRK fusions allows for prompt TRK inhibitor treatment, ensuring durable disease control and functional recovery.
- Increased awareness and use of molecular testing can improve the management of rare pediatric sarcomas.
