Small round cell tumours

Small round cell tumours (SRCT), also small round blue cell tumours (SRBCT), are a group of tumours that have a similar histologic appearance.

It is a group of tumours that is seen more often in childhood than adulthood.

DDx:

• Neuroblastoma.
• Wilms tumour (AKA nephroblastoma).
• Alveolar rhabdomyosarcoma.
• Ewing sarcoma/PNET - this entity is dealt with in the bone tumours article.
• Lymphoma - large cell lymphomas, e.g. diffuse large B cell lymphoma, anaplastic large cell lymphoma.
• Retinoblastoma.
• Hepatoblastoma.
• Desmoplastic small round cell tumour (DSRCT).

Memory device: 4 -blastoma (hepato-, neuro-, nephro-, retino-), PNET/Ewing sarcoma (medulloblastoma), DSRCT, lymphoma, alveolar rhabdomyosarcoma.

Microscopic

Features:

• Sheets of cells, very cellular.
• Small cells ~ 2X RBC diameter.
• Scant cytoplasm.
• Coarse chromatin.
• +/-Nucleolus. (???)
• +/-Vascular.

Tabular comparison

Tumour	Key histologic features	History	Key IHC
Hepatoblastoma		liver	AFP (?)
Neuroblastoma		adrenal gland, sympathetic chain	NB-84
Nephroblastoma (Wilms tumour)	triphasic - (1) blue cells (blastema), (2) spindle cells (stroma), (3) tubular structures (epithelial)	kidney	WT-1
Retinoblastoma		eye
Medulloblastoma
Ewing sarcoma/PNET
Rhabdomyosarcoma			"DAM" = desmin, actin, myogenin
Desmoplastic small round cell tumour (DSRCT)
Small cell carcinoma	stippled chromatin, nuclear moulding		synaptophysin, chromogranin, CD56, keratins
Lymphoma	dyscohesive		CD45

See also

• Soft tissue lesions.