Peripheral Primitive Neuroectodermal Tumor
Supplemental Studies
Immunohistology
| CD99 |
>90% membrane |
| Keratin |
5-15% scattered cells |
| NSE |
40-90% |
| Synaptophysin |
40-50% |
| Chromogranin |
0-25% |
| CD57 |
15-40% |
Histochemical stains
- PAS with and without diastase reveals abundant glygogen in 90% of cases
Genetic study
- Five chromosomal translocations may be seen, all involving EWS gene at 22q12
- t(11;22)(q24;q12) Most common (>80% of cases)
- t(21;22)(q22;q12) Most of the remaining cases
- t(7;22)(p22;q12) Rare
- t(17;22)(q12;q12) Rare
- t(2;22)(q33;q12) Rare
- Under 5% of PPNET / Ewing sarcoma lack detectable translocations involving the EWS gene
