Journal Article

Primary clear cell sarcoma of the femur: a unique case with RT-PCR and direct sequencing confirmation of EWSR1/ATF1 fusion gene

Kubota, Yuta, Tsumura, Hiroshi, Tanaka, Kazuhiro, Daa, Tsutomu, Itonaga, Ichiro, Kawano, Masanori, Iwasaki, Tatsuya, Hisaoka, Masanori

2021

Overview

Background It is very rare for clear cell sarcomas (CCS) to arise in the bone. During diagnosis, it is important to distinguish primary CCS of bone from bone metastasis of melanoma because this difference fundamentally changes the therapeutic options. Recently, characteristic fusion genes of CCS have been detected using reverse transcription polymerase chain reaction (RT-PCR) or direct sequencing which allowed to distinguish CCS from melanoma. However, there was no study applying these analyses with positive results. In this case, we describe the use of fusion gene analysis to diagnose a primary CCS of the bone. Case presentation A 36-year-old male presented with a four-months history of left knee pain. Magnetic resonance imaging showed a lesion in the left femoral medial epicondyle. Histological examination of the biopsy specimen revealed proliferating oval or rounded cells. These cells had clear cytoplasm arranged in fascicles or compact nests with frequent deposits of brown pigment. Furthermore, immunohistochemistry analysis revealed that tumor cells were positive for S-100 protein, HMB-45, Melan-A, and SOX10. It stained negative for CD34 and BRAF v600e. Conclusively, detection of the EWSR1/ATF1 fusion gene using RT-PCR and direct sequencing confirmed that the lesion was a primary CCS of the bone. Wide-margin resection and reconstruction with a tumor endoprosthesis were performed. Conclusions Herein, we diagnosed a rare case of primary CCS of the bone by detecting EWSR1/ATF1 fusion gene using RT-PCR and direct sequencing. Since fluorescence-in situ hybridization (FISH) and RT-PCR could show false positive by mainly due to technical problems, it is better to perform direct sequencing to confidently diagnose the tumor as a primary CCS especially at very rare site such as bone.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
• Subject: Adult / Biopsy / Bone cancer / Case Report / Case reports / Case studies / CD34 antigen / Chemotherapy / Clear cell sarcoma / Cytoplasm / Diagnosis / Direct sequencing / DNA sequencing / Epidemiology / Femur / Femur - metabolism / FLI-1 protein / Fluorescence in situ hybridization / Fusion gene / Fusion protein / Genes / Genetic aspects / Humans / Immunohistochemistry / Internal Medicine / Magnetic resonance imaging / Male / Medicine / Medicine & Public Health / Melanoma / Metastases / Metastasis / Musculoskeletal diseases / Nucleotide sequencing / Oncogene Proteins, Fusion - genetics / Oncogene Proteins, Fusion - metabolism / Orthopedics / Orthopedics and biomechanics / Osteosarcoma / Polymerase chain reaction / Primary bone tumor / Proteins / Radiation therapy / Rehabilitation / Reverse Transcriptase Polymerase Chain Reaction / Reverse transcription / Reverse transcription polymerase chain reaction / Rheumatology / RNA-Binding Protein EWS - genetics / S100 protein / Sarcoma / Sarcoma, Clear Cell - diagnostic imaging / Sarcoma, Clear Cell - genetics / Smooth muscle / Sox10 protein / Sports Medicine / Tumor cells / Tumors