Histopathological findings showed neuroblastoma and immunohistochemical results were as follows: actin(-), CD34(-), CD99(-), CK(-), CgA(+), desmin(-), EMA(-), Ki-67(+, approximately 1%), NSE(+), S-100(+), Syn(+), and vimentin(-).
It is one of the pediatric small round blue cell tumors, characterized by strong membrane expression of CD99 in a chain-mail pattern and negativity for lymphoid (CD45), rhabdomyosarcoma (myogenin, desmin, actin) and neuroblastoma (neurofilament protein) markers.
Differentiation from neuroblastoma may be made based on immunoreactivity for beta 2 microglobulin and HBA71 and lack of immunoreactivity for chromogranin in PPNET and MSCT.