Pediatric primary small round blue cell tumors 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.