FLI1 and neoplasm: Immunohistochemical examination of the tumor with anti-cluster of differentiation (CD)99 and Friend leukemia integration 1 transcription factor (FLI-1) antibodies yielded strongly positive results (Fig. 2c, d), but results for CD34, leukocyte common antigen, terminal deoxynucleotidyl transferase, chromogranin A, and desmin were negative (data not shown).