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

AimsThe 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. MethodsTwo 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. ResultsThe 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. ConclusionsA 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.

Automated summary

This study evaluated the clinicopathological features, immunophenotype, differential diagnosis, molecular genetic features, and prognosis of spindle cell rhabdomyosarcoma with TFCP2 rearrangement. Through histological observation, immunohistochemistry, fluorescence in-situ hybridization, and high-throughput gene sequencing, two cases of spindle cell rhabdomyosarcoma with FET::TFCP2 gene fusion were analyzed. The tumor tissues mainly consisted of spindle cells and epithelioid cells, expressing striated muscle markers and exhibiting high expression levels of CK and ALK protein markers. Molecular detection confirmed the fusion of the FET::TFCP2 gene. A rare case with a double fusion of TIMP3::ALK and FUS::TFCP2 was also observed. This study provides important information on the molecular characteristics of spindle cell rhabdomyosarcoma with FET::TFCP2 fusion, which is characterized by aggressive behavior, poor prognosis, and limited response to therapy. Further exploration of targeted therapy for ALK should be conducted through clinical studies.