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Alexander Drilon, MD

Gregory J. Riely, MD, PhD


Case Series of NTRK-Rearranged Spindle Cell Neoplasms Offers Clinical Insights

By: Celeste L. Dixon
Posted: Thursday, March 16, 2023

Although NTRK-rearranged spindle cell neoplasms—a new category of soft-tissue tumors with NTRK gene fusions—are rare, identifying them properly is crucial because NTRK inhibitors provide highly effective and durable treatment. Hiroshi Kobayashi, MD, PhD, of the University of Tokyo, Japan, and colleagues analyzed the cases of six patients, all of whom had undergone surgery, to investigate the radiologic features of NTRK-rearranged spindle cell neoplasms and their association with histopathologic findings, as well as the patients’ clinical outcomes. Two major findings about NTRK-rearranged spindle cell neoplasms emerged, the team wrote in Molecular and Clinical Oncology: They have high vascularity and tend to infiltrate into surrounding tissue, especially fat tissue.

As such, resection with wide margins is recommended to help avoid local recurrence, stated Dr. Kobayashi and co-investigators. Additionally, their findings suggest that “NTRK-rearranged spindle cell neoplasms should be considered in the differential diagnosis of highly vascular-rich mesenchymal tumors, including solitary fibrous tumors and alveolar soft-part sarcomas.”

Because commonly used assaying methods to identify NTRK fusions—including pan-TRK immunohistochemistry and DNA sequencing using targeted cancer panels—may overlook these tumors, understanding the tumors’ clinical features is vital. The authors confirmed the six patients’ fusion genes using next-generation sequencing, and they assessed the MRI features of all tumors and the histopathologic findings of the resected specimens.

The patients included three women and three men (mean age, 22 years; range, 2–43 years). They had four NTRK1 and two NTRK3 fusions, and three patients were preoperatively diagnosed with solitary fibrous tumors. Five patients had no local recurrences or metastases, but one, with an NTRK3 fusion, experienced both.

“These findings provide useful information for the diagnosis and treatment of NTRK- rearranged spindle cell neoplasms and would aid in improving the detection and curative rates of these tumors,” the authors concluded.

Disclosure: The study authors reported no conflicts of interest.

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