Epithelioid sarcoma is associated with a high percentage of SMARCB1 deletions.
SMARCB1 gene alterations were first described in highly malignant rhabdoid tumors of the kidney, brain (atypical teratoid/rhabdoid tumor) and soft tissue. An increasing number of tumors have now shown loss of SMARCB1 protein expression by immunohistochemistry, including the majority of epithelioid sarcomas. However, investigations of SMARCB1 gene alterations in epithelioid sarcoma have produced conflicting results. The aim of this study was to evaluate SMARCB1 status using Sanger sequencing of the coding region and multiplex ligation-dependent probe amplification, a rapid and sensitive method for detecting intragenic deletions and duplications, which has not been used in previous studies. Twenty-one epithelioid sarcomas of both classical and proximal type were selected for SMARCB1 gene testing and SMARCB1 immunohistochemistry. Nineteen of 21 (90%) epithelioid sarcomas were SMARCB1 negative by immunohistochemistry. Twelve of the 19 (63%) had adequate DNA recovery for evaluation. Ten of 12 (83%) tumors showed homozygous deletions of the gene. Two cases showed heterozygous deletions and polymorphisms, but no sequence mutations. These results confirm the high frequency of SMARCB1 deletions in epithelioid sarcoma and show that multiplex ligation-dependent probe amplification is a reliable method for detection of deletions in these cases, which can be performed on formalin-fixed, paraffin-embedded tissue. Given the high percentage of SMARCB1 alterations in epithelioid sarcoma, these findings argue against using SMARCB1 gene deletion as a tool in distinguishing them from malignant rhabdoid tumors.
Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia, Perelman School of Medicine of the University of Pennsylvania, Philadelphia, PA, USA. sullivanl@email.chop.edu
Lisa M
LM
Sullivan
Andrew L
AL
Folpe
Bruce R
BR
Pawel
Alexander R
AR
Judkins
Jaclyn A
JA
Biegel
D000293:Adolescent; D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis / Q000235:genetics*; D002868:Chromosomal Proteins, Non-Histone / Q000032:analysis / Q000235:genetics*; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000032:analysis / Q000235:genetics*; D003937:Diagnosis, Differential; D005091:Exons; D005260:Female; D017353:Gene Deletion; D020022:Genetic Predisposition to Disease; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D008910:Minnesota; D060885:Multiplex Polymerase Chain Reaction; D010641:Phenotype; D015143:Philadelphia; D011110:Polymorphism, Genetic; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D000071796:SMARCB1 Protein; D012509:Sarcoma / Q000737:chemistry / Q000235:genetics* / Q000473:pathology; D012983:Soft Tissue Neoplasms / Q000737:chemistry / Q000235:genetics* / Q000473:pathology; D014157:Transcription Factors / Q000032:analysis / Q000235:genetics*; D055815:Young Adult
D014408:Biomarkers, Tumor; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D000071796:SMARCB1 Protein; C513266:SMARCB1 protein, human; D014157:Transcription Factors