LMNA-NTRK1-rearranged spindle cell neoplasm with multiple relapses: a case report and literature review

Neurotrophic tyrosine receptor kinase (NTRK)-rearranged spindle cell neoplasms (NTRK-RSCNs) constitute a rare, heterogeneous subset of soft tissue tumors defined by oncogenic fusions involving NTRK1, NTRK2, or NTRK3 genes. Despite the remarkable efficacy of TRK inhibitor therapy in fusion-positive tumors, the histomorphologic variability of NTRK-RSCNs poses significant diagnostic challenges, and data on malignant transformation remain limited. Herein, we report a unique case of LMNA::NTRK1-rearranged spindle cell neoplasm in a 23-year-old woman, characterized by previously undescribed pigmentation, multiple local recurrences, and fibrosarcoma-like malignant transformation-features that have not been documented in prior literature. Through integrated histopathological, immunohistochemical, and molecular analyses, we characterize the diagnostic nuances, biological behavior, and potential drivers of progression in this entity. Our findings expand the morphological and clinical spectrum of LMNA::NTRK1-rearranged tumors and highlight the need for close follow-up and consideration of adjuvant targeted therapy in high-risk cases.