Small round blue cell tumor: a group of childhood tumors that is characterized by a similar appearance under the microscope. The appearance is that of small, round, primitive cells that stain blue with conventional staining techniques for biopsy analysis. The small round blue cell tumors include neuroblastoma, rhabdomyosarcoma, non-Hodgkin's lymphoma, and the Ewing's family of tumors. Sometimes other tumor types are included in this group. In any case, small round blue cell tumors are malignant tumors that are hard to distinguish from each other using conventional microscopic analysis. Specialized laboratory testing, including molecular diagnostic tests, are used to differentiate one type of these tumors from another. It is essential to determine the exact type of tumor, because the treatments for these tumors are different based on their type.
Lewis, TB. et al. "Differentiating Ewing's sarcoma from other round blue cell tumors using a RT-PCR translocation panel on formalin-fixed paraffin-embedded tissues." Modern Pathology (2007) 20, 397–404.