Excellent response to trametinib and low dose chemotherapy in a patient with rare RAF1 mutated sarcoma in a tertiary care center in India.

With the advent of next-generation sequencing, increasingly we can sub classify the soft tissue sarcomas into various subtypes with distinct prognostic and therapeutic implications. Sarcomas with RAF1 mutations are extremely rare and so far, the treatment strategies are not known. Here, we report a case of a 48-year-old lady who initially presented with right ear swelling, which was excised and was suggestive of dermatofibrosarcoma protuberans with S100 expression. After a disease-free interval of 25 months, the patient relapsed with metastasis in the lung. Repeat biopsy and next-generation sequencing (NGS) were suggestive of PDZRN3/RAF1 fusion mutated sarcoma. On presentation, the patient had an Eastern Cooperative Oncology Group performance status of 4 and had respiratory distress due to lung metastasis. After consensus and decision in the molecular tumour board, the patient was started on low-dose trametinib and doxorubicin. After three cycles of treatment, the patient had a partial response and post six cycles she had a near-complete response. This case exemplifies the value of molecular characterisation of soft tissue sarcoma and adds to the already sparse literature for RAF1 mutated sarcomas.