=====Small round blue cell tumor===== Pediatric primary [[small round blue cell tumor]]s in the CNS represent several entities, some more common than others. In histopathology, a small-, round-, blue-cell tumor (abbreviated SRBCT), also known as a small-blue-round-cell tumour (SBRCT) or a small-round-cell tumour (SRCT), is any one of a group of malignant neoplasms that have a characteristic appearance under the microscope, i.e. consisting of small round cells that stain blue on routine H&E stained sections. These tumors are seen more often in children than in adults. They typically represent undifferentiated cells. The predominance of blue staining is due to the fact that the cells consist predominantly of nucleus, thus they have scant cytoplasm. Tumors that belong to this group are: Desmoplastic small-round-cell tumour [[Ewing's Sarcoma peripheral primitive neuroectodermal tumor]] Neuroblastoma [[Medulloblastoma]] Rhabdomyosarcoma Synovial Sarcoma Carcinoid tumor Mesotelioma Variante cromófoba do tumor de células renais Leiomiossarcoma Small cell lung cancer Wilms' tumour Retinoblastoma Small-cell lymphoma Hepatoblastoma- only the anaplastic form has round blue cells, the more common fetal and embryonal types do not Merkel cell carcinoma Endometrial stromal condensation may mimic a small-blue-round-cell tumour.