IMMUNOHISTOCHEMISTRY: FLI-1

FLI-1 NUCLEAR TRANSCRIPTION FACTOR HAS BEEN PROPOSED AS A USEFUL TOOL IN THE DIFFERENTIAL DIAGNOSIS OF SMALL ROUND CELL TUMORS. FLI-1 AIDS IN PHENOTYPING ENDOTHELIAL-DERIVED TUMORS, EWING SARCOMA, MERKEL CELL CARCINOMA, LUNG ADENOCARCINOMA, MELANOMA AND ERYTHROLEUKEMIA. A CHROMOSOMAL TRANSLOCATION BETWEEN THE FLI-1 GENE AND THE EWS GENE IS FOUND IN MOST EWING SARCOMAS. IN NORMAL TISSUES, NUCLEAR STAINING FOR FLI-1 IS SEEN IN ENDOTHELIAL CELLS, A SUBSET OF T CELLS, MEGAKARYOCYTES AND NORMAL BREAST EPITHELIUM. LACK OF EXPRESSION IS SEEN IN RHABDOMYOSARCOMA, DESMOPLASTIC ROUND CELL TUMORS AND ADENOCARCINOMA COLON.