The frequency of p53, Ki67, CD99 and Fli-1 protein expression in paraffin-embedded tissue blocks in Ewing's sarcoma

Ewing sarcoma family tumors (ESFTs) are among the most malignant tumors in children and young adults. ESFTs include Ewing sarcoma (ES) and peripheral primitive neuroectodermal tumors (pPNETs). As there seemed to be few studies on the molecular biology of ESFTs, we investigated the frequency of CD99, Ki67, p53 and Fli-1 protein expression in 15 Iranian patients with ESFTs. In addition, the correlation between expression rate of these proteins and various clinical factors, including age, sex and survival was computed.

The expression of the aforesaid proteins was studied by immunohisto-chemistry in formalin-fixed and paraffin-embedded blocks of 15 ESFTs specimens. Stained sections were classified according to the percentage of stained tumor cells.

The results showed the membrane expression of CD99 protein in all of the specimens. The nuclear expression of Fli-1 protein was observed in 86.7% and the over-expression of p53 nuclear protein was seen in 53.3% of the specimens. The expression rate of Ki67 protein was 60%. Although a significant correlation was not shown between the expression levels of Ki67, p53 or Fli-1 proteins with age, sex or survival of the patients, there was a significant correlation between expression levels of p53 and Ki67 proteins (P=0.003).

The results underline the role of p53 and Ki67 proteins in the development and progression of ESFTs and suggest the simultaneous immunohistochemical staining of Fli-1 and CD99 proteins for the diagnosis of ESFTs.