title: BCOR-CCNB3-positive soft tissue sarcoma with round-cell and spindle-cell histology: a series of four cases highlighting the pitfall of mimicking poorly differentiated synovial sarcoma.
abstract: OBJECTIVE
  BCOR-CCNB3 sarcoma is a genetically defined undifferentiated malignancy with Ewing sarcoma (ES)-like round cells, and preferentially affects the bones of male adolescents. Sarcomas harbouring BCOR-CCNB3 rarely arise from soft tissues; therefore, we aimed to report four cases to expand the clinicopathological spectrum.
  
  
  RESULTS
  By reverse transcription polymerase chain reaction and confirmatory sequencing, we detected a BCOR-CCNB3 transcript in primary undifferentiated sarcomas of the deep musculature of four male patients, comprising two teenagers (aged 14 and 17 years) and two adults (aged 34 and 44 years). The tumours originated in the back (n = 2), pelvis (n = 1), and thigh (n = 1), and were 70-140 mm in size (mean, 107 mm). All tumours showed sheets of primitive round or ovoid cells with vesicular nuclei, active mitosis (28-41/10 high-power fields), variably prominent nucleoli, and geographical necrosis. This major component transformed into fascicles of elongated spindle cells with staghorn vessels and a myxoid reticular stroma, accounting for 10-50% of areas. All cases were positive for CD99, three were positive for TLE1, and one was positive for EMA, indicating poorly differentiated synovial sarcomas (PDSSs). Nuclear cyclin B3 reactivity was present in all cases, but not in molecularly confirmed atypical ESs and PDSSs. At the last follow-up (median, 13.5 months), one patient had died of lung metastasis, two were alive with tumours, and one was tumour-free.
  
  
  CONCLUSIONS
  BCOR-CCNB3-positive sarcomas may primarily occur in soft tissues of adults and show PDSS-mimicking round-cell and spindle-cell histology with aggressive behaviour. Cyclin B3 is useful for selecting candidates for BCOR-CCNB3 molecular testing.
authors.affiliation: Department of Pathology, E-DA Hospital, I-Shou University, Kaohsiung, Taiwan.|Bone and Soft Tissue Study Group, Taiwan Society of Pathology, Kaohsiung, Taiwan.
authors.forename: Wan-Shan
authors.initials: WS
authors.lastname: Li
authors.affiliation: Bone and Soft Tissue Study Group, Taiwan Society of Pathology, Kaohsiung, Taiwan.|Department of Pathology, National Cheng Kung University Hospital, Tainan, Taiwan.
authors.forename: I-Chuang
authors.initials: IC
authors.lastname: Liao
authors.affiliation: Bone and Soft Tissue Study Group, Taiwan Society of Pathology, Kaohsiung, Taiwan.|Department of Pathology and Laboratory Medicine, Taichung Veterans General Hospital, Taichung, Taiwan.
authors.forename: Mei-Chin
authors.initials: MC
authors.lastname: Wen
authors.affiliation: Department of Radiology, Taichung Veterans General Hospital, Taichung, Taiwan.|School of Radiological Technology, Central Taiwan University of Science and Technology, Taichung, Taiwan.
authors.forename: Howard Haw-Chang
authors.initials: HH
authors.lastname: Lan
authors.affiliation: Department of Anatomical Pathology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
authors.forename: Shih-Chen
authors.initials: SC
authors.lastname: Yu
authors.affiliation: Bone and Soft Tissue Study Group, Taiwan Society of Pathology, Kaohsiung, Taiwan. a120600310@yahoo.com.|Department of Anatomical Pathology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan. a120600310@yahoo.com.
authors.forename: Hsuan-Ying
authors.initials: HY
authors.lastname: Huang
mesh_terms: D000293:Adolescent; D000328:Adult; D014408:Biomarkers, Tumor / Q000032:analysis*; D019926:Cyclin B / Q000235:genetics*; D003937:Diagnosis, Differential; D006801:Humans; D008297:Male; D015514:Oncogene Proteins, Fusion / Q000032:analysis; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D012097:Repressor Proteins / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012509:Sarcoma / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D013584:Sarcoma, Synovial / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D012983:Soft Tissue Neoplasms / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology
chemical_list: C411984:BCOR protein, human; D014408:Biomarkers, Tumor; C503694:CCNB3 protein, human; D019926:Cyclin B; D015514:Oncogene Proteins, Fusion; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins
keywords: 
  BCOR-CCNB3
  ; Ewing sarcoma; round; spindle; synovial sarcoma