Immunohistochemical evaluation of small round cell tumors of childhood

Objective: This study was done to evaluate the pediatric undifferentiated small round cell tumors with immunohistochemical staining. Setting: The present study included consecutive cases of small round cell rumors which were diagnosed in children (<15 years) in the section of Histopathology at the Aga Khan University Hospital, Karachi during the period of two years. Methods: The group of undifferentiated small round cell tumors were evaluated immunohistochemically by using a panel of antibodies on sections from routinely processed, formalin fixed, paraffin embedded tissue blocks. Results: The category of undifferentiated small round cell tumors included rhabdomyosarcoma (23.2%), primitive neuroectodermal tumor (17.9%) , non-Hodgkin's lymphoma (16.1%), neuroblasloma (14.2%), Ewing's sarcoma (10.7%) in order of frequency. Osteosarcoma (Small cell variant), retinoblastoma and medulloblastoma comprised 1.8% each. In seven cases (12.5%), the immunohistochemical analysis was inconclusive. Conclusion: Immunohistochemistry is a very valuable diagnostic tool which helps in distinguishing the undifferentiated tumors especially small round cell tumors. The immunohistochemical staining needs to be performed routinely for undifferentiated tumors in diagnostic histopathology.