Stains
FLI1

Author: Lauren Stuart, M.D. (see Authors page)

Revised: 16 December 2015, last major update June 2013

Copyright: (c) 2003-2015, PathologyOutlines.com, Inc.

PubMed Search: FLI1
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's sarcoma (sensitive and specific marker)
    • 90% of Ewing’s sarcoma / primitive neuroectodermal (PNET) tumors have t(11;22)(q24;q12), which results in fusion of EWS to FLI1
    • Distinguish Ewing’s sarcoma / PNET of kidney (positive) from blastema predominant Wilms’ tumor (negative)
    • Distinguish Ewing's sarcoma / PNET (positive) from small cell osteosarcoma or mesenchymal chondrosarcoma (negative, Appl Immunohistochem Mol Morphol 2011;19:233)
  • Sensitive and specific for vascular tumors vs. sarcomas, carcinomas or melanomas (Am J Surg Pathol 2001;25:1061)
Micro Images

Images hosted on other servers:

D: normal kidney

D: normal spleen & lymph node

Ewing's sarcoma / PNET


Maxilla: desmoplastic small round cell tumor

Various tumour types

Merkel cell carcinoma (negative)



Images hosted on Nature.com:

Pancreas: solid pseudopapillary neoplasm

Ewing's sarcoma / PNET

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 non-vascular sarcoma