Sarcoma with CIC-rearrangement

Sarcoma with CIC-rearrangement
Diagnosis in short
Synonyms	CIC-DUX sarcoma
LM	small round blue cell tumour with focal cytoplasmic clearing +/-zonal necrosis
LM DDx	Ewing sarcoma, other Ewing-like tumours, DSRCT, other small round cell tumours
IHC	WT-1 +ve, CD99 +ve/-ve (not strong membranous), ERG +ve, FLI-1 +ve
Molecular	t(4;19)(q35;q13.1) present, EWSR1 abnormality absent
Site	soft tissue
Prevalence	very rare
Prognosis	poor
Clin. DDx	other soft tissue tumours
Treatment	wide excision (?)

Undifferentiated small blue round cell sarcoma with t(4;19), is a rare malignant small round cell tumour.

It is also known as CIC-DUX sarcoma. CIC-DUX is pronounced "six ducks"

General

• Rare.
• Young - typically 20s.
• Female>male.
• Aggressive course.

Microscopic

Features:

• Small round cell tumour.
  • Patchy cytoplasmic clearing.
  • Necrosis.

DDx:

• Ewing sarcoma.
• Other Ewing-like tumours.
• Desmoplastic small round cell tumour.
• Other small round cell tumours.

IHC

• CD99 +ve/-ve
  • Not strong and membranous.
• WT-1 +ve.
• S-100 -ve.
• Desmin -ve.
• Myogenin -ve.
• ERG +ve.
• FLI-1 +ve.

Molecular

• t(4;19)(q35;q13.1).
  • CIC-DUX4 fusion.
• EWSR1 FISH negative.

See also

• Small round cell tumour.