Utility of characteristic 'Weak to Absent' INI1/SMARCB1/BAF47 expression in diagnosis of synovial sarcomas.
Recently, very few studies have shown value of immunohistochemical (IHC) expression of INI1/SMARCB1 in diagnosis of synovial sarcomas (SSs). This study was aimed at testing reproducibility and utility of this finding. Sixty-eight SSs and 147 other tumours, in the form of various biopsies, were tested for IHC expression of INI1. Twenty-six SSs were further confirmed with positive SS18 rearrangement. Forty monophasic spindle cell type (58.8%), 13 biphasic (19.1%), 12 poorly differentiated (17.6%) and three calcifying SSs (4.4%) were positive for epithelial membrane antigen (EMA) (46/62) (74.1%), pan cytokeratin (AE1/AE3) (31/47) (65.9%), cytokeratin (CK7) (20/31) (64.5%), BCL2 (62/66) (93.9%), MIC2 (61/63) (96.8%), transducin-like enhancer of split 1 (TLE1) (29/31) (93.5%) and CK19 (14/24) (58.3%). INI1 expression was 'weak to absent' in 60/68 (88.2%) SSs; in 1/3 atypical ossifying fibromyxoid tumours (AOFMTs) and in 3/10 (30%) malignant peripheral nerve sheath tumours (MPNSTs) of various types. INI1 was completely absent in 10/10 (100%) epithelioid sarcomas (ESs), 4/4 (100%) malignant rhabdoid tumours, single paediatric undifferentiated sarcoma, 5/19 (26.3%) myoepithelial carcinomas and in 2/4 (50%) epithelioid-subtype of MPNSTs. Remaining 100 tumours, including 12 Ewing sarcomas, 15 carcinomas, eight solitary fibrous tumours (SFT), seven extraskeletal myxoid chondrosarcomas, three fibrosarcomas and other tumours retained INI1 expression. A unique 'weak to absent' IHC expression of INI1 is highly sensitive (88.2%) and specific (97.3%) for a SS, irrespective of its subtypes and types of biopsies. This can be considered useful in diagnosing SSs, especially in settings lacking molecular and/or cytogenetic analysis. A similar INI1 expression is shared by certain AOFMTs and MPNSTs.
Department of Pathology, Tata Memorial Centre, Parel, Mumbai, India.
Bharat
B
Rekhi
Institute of Pathology, University Hospital Tuebingen, Eberhard-Karls-University, Tuebingen, Germany.
Ulrich
U
Vogel
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002813:Chondrosarcoma / Q000175:diagnosis / Q000235:genetics / Q000473:pathology; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D018204:Neoplasms, Connective and Soft Tissue / Q000175:diagnosis / Q000235:genetics / Q000473:pathology; D018317:Nerve Sheath Neoplasms / Q000175:diagnosis / Q000235:genetics / Q000473:pathology; D015203:Reproducibility of Results; D018335:Rhabdoid Tumor / Q000175:diagnosis / Q000235:genetics / Q000473:pathology; D000071796:SMARCB1 Protein; D012509:Sarcoma / Q000175:diagnosis / Q000235:genetics / Q000473:pathology; D013584:Sarcoma, Synovial / Q000175:diagnosis* / Q000235:genetics* / Q000473:pathology; D012680:Sensitivity and Specificity; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D055815:Young Adult
D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D000071796:SMARCB1 Protein; C513266:SMARCB1 protein, human; D014157:Transcription Factors
22q11.2; INI1/SMARCB1/BAF47; immunohistochemistry of soft tissue sarcomas; synovial sarcoma