This glycoprotein is a cell adhesion factor that can be found in different neoplasms; in SFT its expression is observed in 81-95% of cases.14 As mentioned above, CD99 has been used as an alternative marker for SFT diagnosis, but its sensitivity rate is lower (75%).9 In our case, CD99 was negative, as pointed out in other studies.13 Thus, although CD99 has been described as an important alternative marker for SFT, it cannot be considered a predictor for diagnosis. This evidence concerns the gene CD99 and neoplasm.