Purpuric Patches as Cutaneous Presentation of Pediatric NTRK-Rearranged Spindle Cell Neoplasm.

Neurotrophic tyrosine receptor kinase-rearranged spindle cell neoplasms (NTRK-RSCNs) are rare soft tissue tumors with a broad histologic spectrum. Limited data exist on their cutaneous manifestations, particularly in pediatric patients. We present the case of a 4-year-old girl with an LMNA-NTRK1 fusion-positive spindle cell neoplasm initially presenting as a subcutaneous nodule adjacent to purpuric patches on the abdomen. This case highlights an atypical cutaneous presentation of NTRK-RSCNs and demonstrates the successful use of larotrectinib, a TRK inhibitor, in achieving both clinical and histological remission.