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 tumors 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%), neuroblastoma (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.