Affiliation:
1. Department of Pathology, The University of Hong Kong, Queen Mary Hospital, HKSAR
2. Department of Orthopaedics and Traumatology, The University of Hong Kong, Queen Mary Hospital, HKSAR
Abstract
Soft tissue tumors with RAF1 fusion had been emerging as a group of tumors with peculiar histology and immunoprofile. While a case series and rare case reports of RAF1 translocated sarcoma had been reported, to our knowledge a primary bone tumor with RAF1 translocation and fusion partner with MAP4 had not been described in the literature. The patient was a 60-year-old lady, with strong family history of breast cancer, who presented with pathological fracture of right humerus. X-ray revealed a 9.7 cm juxta-articular lesion of the proximal humerus, which was expansile and lytic with a non-sclerotic well defined border distally, radiologically suggestive of a giant cell tumor of bone. Excision was performed after initial biopsy. Histology showed a monomorphic low grade spindle cell lesion with prominent hyalinized stroma. Immunohistochemistry demonstrated diffuse CD34 staining, with focal staining for S100. Gene sequencing for histone 3 H3 genes was negative for hotspot mutation. Targeted RNA-seq sequencing revealed the presence of MAP4::RAF1 fusion, which was confirmed by reverse transcriptase-polymerase chain reaction (RT-PCR) and fluorescence in-situ hybridization (FISH) break-apart probes involving both genes. The overall features were consistent with a primary bone sarcoma with RAF1 fusion. This report expanded the spectrum of RAF1 fusion sarcoma and was the first report documenting its primary occurrence in bone.
Subject
Pathology and Forensic Medicine,Surgery,Anatomy
Cited by
2 articles.
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