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	solid variant of alveolar rhabdomyosarcoma, embryonal rhabdomyosarcoma, 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.

Clinics

• Rare cases in the CNS reported.

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.
• Other small round cell tumours.

Images

• 

  DSRCT - intermed. mag. (WC/Nephron)

• 

  DSRCT - high mag. (WC/Nephron)

• 

  DSRCT - very high mag. (WC/Nephron)

IHC

Features:

• AE1/AE3 +ve.
• CAM5.2 usu -ve.
• Desmin +ve (strongly).
• EMA +ve.
• Actin -ve.
• WT-1 (N-terminal) -ve.
• WT-1 (C-terminal) +ve (nuclear staining).
• CD57 +ve.
• Synaptophysin focal, patchy +ve.

Molecular

• t(11;22)(p13;q12).

See also

• Soft tissue lesions.
• Small round cell tumours.
• Stromal desmoplasia.