Clinicopathological features of rhabdomyosarcoma with novel FET::TFCP2 and TIMP3::ALK fusion: report of two cases and literature review

Aims The aim of this study was to evaluate the clinicopathological features, immunophenotype, differential diagnosis, molecular genetic features and prognosis of spindle cell rhabdomyosarcoma with TFCP2 rearrangement. Methods Two cases of spindle cell rhabdomyosarcoma with FET::TFCP2 gene fusion were included in this study. Samples were collected and evaluated through histological observation, immunohistochemistry, fluorescence in‐situ hybridisation and high‐throughput gene sequencing and previous findings. Results The tumour tissues mainly comprised spindle cells and epithelioid cells, which expressed striated muscle markers, and exhibited high expression levels of CK and ALK protein markers. Molecular detection showed that the FET::TFCP2 gene was fused. A rare case with TIMP3::ALK and FUS::TFCP2 double‐fusion was observed in this study. Conclusions A case with double fusion of ALK and TFCP2 was reported in rhabdomyosarcoma for the first time in this study, which provides information on the molecular characteristic of the tumour. Spindle cell rhabdomyosarcoma with FET::TFCP2 fusion is characterised by histological, immunohistochemical and genetic changes. The tumour is aggressive, with poor prognosis and poor response to radiotherapy and chemotherapy. The efficacy of targeted therapy for ALK should be explored through more clinical studies. Two cases of spindle cell rhabdomyosarcoma with FET::TFCP2 gene fusion were included in this study. A case with FUS::TFCP2 and TIMP3::ALK double‐fusion was reported in rhabdomyosarcoma for the first time in this study, which provides information on the molecular characteristic of the tumour.