11 - IHC Approach to the differential diagnosis of small blue round cell tumors - Dr. Armen Mkhitary

Small, blue, round cell tumors (SBRCT) is a group of highly heterogeneous malignant and aggressive tumors, which can occur at any age.Tumors in this group are sharing similar morphological appearance, and characterized by small, round nuclei and a narrow cytoplasm, thus gaining more blue color in H&E stained slides.The tumors of this group, which more commonly encountered in children include lymphoblastic lymphoma, Ewing’s sarcoma, rhabdomyosarcoma, nephroblastoma, neuroblastoma, medulloblastoma, retinoblastoma, and hepatoblastoma.Other tumors, such as small cell carcinoma, Merkel cell carcinoma, non-Hodgkin lymphoma, synovial sarcoma, desmoplastic round cell tumor, mesenchymal chondrosarcoma, small cell osteosarcoma and olfactory neuroblastoma are traditionally accepted to be more common in adults.Differential diagnosis of these tumors is difficult and sometimes challenging for pediatric pathologists. Despite the similar immunohistochemical expression patterns of some antigens (CD56, CD99), we discuss and present our insight of this problem.