Biological Adaptations in Rhabdomyosarcoma Tumor Cells in lymph nodes: A Case Report of RMS with FUS::TFCP2 translocation

Abstract Introduction/Objective The WHO classification categorizes Rhabdomyosarcoma (RMS) into four main subtypes based on clinicopathological and molecular features. However, TFCP2-rearranged RMS, a rare tumor, does not neatly fit into any of these subtypes. Literature review identified only two reported cases of RMS with FUS::TFCP2 fusion and a round cell component. Methods/Case Report We present a rare case of RMS in lymph nodes with FUS::TFCP2 translocation in a 29-year- old female with a history of spindle cell rhabdomyosarcoma in the bilateral maxilla. The original tumor exhibited a distinctive spindle and epithelioid phenotype, coexpressing myogenic markers, epithelial markers, and ALK. FUS::TFCP2 translocation was confirmed, representing an uncommon subset of RMS. After chemotherapy, radiation, and surgery, the patient developed multiple bilateral pathologically enlarged cervical lymph nodes. Excision revealed metastatic rhabdomyosarcoma involving lymph nodes with a predominantly round cell and epithelioid morphology, with approximately 5% spindle cell growth, resembling the pattern identified in the primary resection. Results (if a Case Study enter NA) NA Conclusion Previous reports suggest that RMS with FUS::TFCP2 fusion displays a biphasic pattern, comprising solid proliferation of round cells in superficial areas and spindle cells in deeper regions. The altered cell morphology observed in our case may be attributed to the varied distribution pattern of each component with lesion depth and the cellular stress response. Previous literature reported that radiation stress potentially leads to biological adaptations of tumor cells and tumor radioresistance. Our findings underscore the distinctive phenotype of RMS with FUS::TFCP2 fusion, characterized by the coexpression of myogenic and epithelial markers, along with ALK positivity. Understanding the cellular adaptations of RMS cells could inform the development of novel clinical interventions aimed at enhancing radiosensitization and improving therapeutic efficacy, ultimately enhancing patient survival.