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/PNET
- Synovial Sarcoma
- Carcinoid tumor
- 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.
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- aved Khan1, Jun Wei1, Lao Saal1, Ladanyi Marc2, Ringnér Markus3, Carsten Peterson3, Yidong Chen1 & Paul Meltzer1. "Development of a molecular taxonomy of small blue round-cell tumors using cDNA microarrays - Nature Genetics".
- Chen QR, Vansant G, Oades K et al. (February 2007). "Diagnosis of the small round blue cell tumors using multiplex polymerase chain reaction". J Mol Diagn 9 (1): 80–8. doi:10.2353/jmoldx.2007.060111. PMC 1867426. PMID 17251339.
- Gray W, Kocjan G. Diagnostic Cytopathology; . p.307