Identification of a novel MTAP-RAF1 fusion in a soft tissue sarcoma

BACKGROUND: RAF family activating fusions have been described as a potentially targetable molecular finding in a subset of soft tissue sarcomas. To further expand upon the landscape of this genetic feature, we describe a novel MTAP-RAF1 activating fusion identified in a S100 positive soft tissue sarcoma. CASE PRESENTATION: A 51 year old man underwent excision of a soft tissue mass in his foot. Pathology revealed a spindle cell neoplasm with S100 positivity, ultimately classified as a soft tissue sarcoma, not otherwise specified. Comprehensive molecular profiling was performed to help establish the diagnosis and revealed a novel MTAP-RAF1 fusion that includes the tyrosine kinase domain of RAF1. CONCLUSIONS: Our report adds to the spectrum of fusion-driven RAF activation observed in soft tissue sarcomas and lends additional evidence that RAF activation plays an important role in some soft tissue sarcomas. Identification of novel fusions involving the MAPK/ERK pathway in sarcomas may provide new avenues for precision medicine strategies involving targeted kinase inhibitors.