Desmoplastic small round cell tumour

Desmoplastic small round cell tumour
Diagnosis in short
DSRCT. H&E stain.
LM	small (round) cells in nests with an undulating sharp border, road bands of paucicellular fibrous stroma
LM DDx	Embryonal RMS, other small round cell tumours
IHC	AE1/AE3 +ve, desmin +ve, EMA +ve, actin -ve, WT1 (N-terminal) -ve, WT1 (C-terminal) +ve, CD57 +ve.
Molecular	t(11;22)
Site	soft tissue lesions - typically retroperitoneum
Clinical history	usu. young adults
Prevalence	very rare
Prognosis	poor
Clin. DDx	(metastatic) germ cell tumour, lymphoma

Desmoplastic small round cell tumour, abbreviated DSRCT, is a rare malignant soft tissue lesion that tends to afflict young adults.

General

• Males > females.
• Usu. affects young adults.
• Typically retroperitoneal.
• Poor prognosis.

Microscopic

Features:

1. Broad bands of paucicellular fibrous stroma with:
2. Small round cells in nests with an undulating sharp border.
   • The small round cells lack distinct nucleoli and have scant cytoplasm; they are small round cell tumour cells.

Notes:

• Usu. abundant mitoses.
• +/-Necrosis.

DDx:

• Metastatic germ cell tumour (DDx of location and age).
• Embryonal RMS.
  • It should be noted that DSRCT, like embryonal RMS, is +ve for desmin!
• Solid variant of alveolar RMS.
  • Nests in alveolar RMS have round edges.

Images

• 
  DSRCT - intermed. mag. (WC/Nephron)
• 
  DSRCT - high mag. (WC/Nephron)
• 
  DSRCT - very high mag. (WC/Nephron)

IHC

Features:

• AE1/AE3 +ve.
• Desmin +ve.
• EMA +ve.
• Actin -ve.
• WT1 (N-terminal) -ve.
• WT1 (C-terminal) +ve.
• CD57 +ve.

Molecular

• t(11;22)(p13;q12).

See also

• Soft tissue lesions.