Fine needle aspiration biopsy of pediatric orbital tumors. An immunocytochemical study.

Specific antibodies against neuron-specific enolase, leukocyte common antigen and desmin were assessed for their usefulness in the cytodiagnosis of 23 cases of pediatric orbital round cell tumors (10 cases of orbital recurrence of retinoblastoma, 11 cases of embryonal rhabdomyosarcoma and 2 cases of inflammatory pseudotumor). Alcohol-fixed, Papanicolaou-stained smears were decolorized and stained with monoclonal antisera using the peroxidase-antiperoxidase procedure. Twenty of 23 aspirates were positively immunostained with antisera against leukocyte common antigen, desmin and neuron-specific enolase. Eight of 10 cases of clinically diagnosed orbital recurrence of retinoblastoma showed strong monotypic staining with anti-neuron-specific enolase antiserum. More than 50% of tumor cells in 9/11 cases of embryonal rhabdomyosarcoma were also immunopositive with this antiserum. Desmin positivity was seen in 10/11 cases of embryonal rhabdomyosarcoma, whereas immunopositivity with leukocyte common antigen was detected in both cases of inflammatory pseudotumor. These results indicate that the use of a panel of monoclonal antibodies on aspirate smears is imperative for establishing the diagnosis and classification of pediatric round cell orbital tumors.