Stains & CD markers

Topic Completed: 1 June 2013

Minor changes: 10 September 2021

Copyright: 2003-2021,, Inc.

PubMed Search: FLI1

Lauren N. Stuart, M.D., M.B.A.
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Cite this page: Stuart L. FLI1. website. Accessed September 20th, 2021.
Definition / general
  • Protein is member of ETS family of DNA binding transcription factors; gene is fli-1, on #11q24
  • Also called Friend leukaemia integration-1
  • Involved in cellular proliferation, tumorigenesis and embryologic development of blood vessels
  • Interpretation: call positive if nuclear staining of 10% of tumor cells (usually is > 50%) and positive internal controls of endothelial cells and small lymphocytes (Am J Surg Pathol 2001;25:1061)
  • Note: other vascular tumor markers (CD31, CD34 and von Willebrand factor) are membranous or cytoplasmic stains
  • Note: cytoplasmic staining is present in breast epithelium (benign / malignant) and cutaneous eccrine glands
Uses by pathologists
  • Diagnosis of Ewing sarcoma (sensitive and specific marker)
    • 90% of Ewing sarcoma / primitive neuroectodermal (PNET) tumors have t(11;22)(q24;q12), which results in fusion of EWS to FLI1
    • Distinguish Ewing sarcoma / PNET of kidney (positive) from blastema predominant Wilms tumor (negative)
    • Distinguish Ewing sarcoma / PNET (positive) from small cell osteosarcoma or mesenchymal chondrosarcoma (negative, Appl Immunohistochem Mol Morphol 2011;19:233)
  • Sensitive and specific for vascular tumors versus sarcomas, carcinomas or melanomas (Am J Surg Pathol 2001;25:1061)
Microscopic (histologic) images

Images hosted on other servers:

D: normal kidney

D: normal spleen and lymph node

Ewing sarcoma / PNET

Maxilla: desmoplastic small round cell tumor

Various tumour types

Merkel cell carcinoma (negative)

Positive staining - normal
  • Endothelial cells, T cells and small lymphocytes
Positive staining - disease
Negative staining
  • Muscle, nerve and fibroblasts
  • Blastema predominant Wilms tumor
  • Carcinoma and nonvascular sarcoma
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