Atypical teratoid/rhabdoid tumour

Atypical teratoid/rhabdoid tumour, abbreviated AT/RT, is malignant tumour usually found supratentorially.

It may be written atypical teratoid rhabdoid tumour, i.e. without the forward slash (abbreviated ATRT, or atypical teratoid-rhabdoid tumour (abbreviated AT-RT).

It should not be confused with the extrarenal malignant rhabdoid tumour.

General

• Usually supratentorial, occasionally in posterior fossa, case reports of spinal cord.

Microscopic

Features:

• Cellular.
• Small round cells usu. with a prominent nucleolus.
• Rhabdoid cells.
  • Cells with eosinophilic granular cytoplasm + eccentric nucleus.
• Mitoses.
• +/-Necrosis (common).

DDx:

• Primitive neuroectodermal tumour (PNET).
• Medulloblastoma.
• Diffuse astrocytoma.
• Choroid plexus carcinoma.
• Embryonal carcinoma.

Images

• 

  Rhabdoid tumour cell. (WC)

• 

  AT/RT. (WC)

• 

  AT/RT -ve for INI1. (WC)

www:

• AR/RT (upmc.edu).

IHC

• BAF-47 -ve (AKA INI1, AKA SMARCB1 - the HGNC symbol) - virtually diagnostic.
  • Endothelial cells +ve control.
• S-100 +ve.
  • Few other brain tumours express it.
• Vimentin +ve (perinuclear condensation).

Others:

• GFAP +ve (focal - in tumour cells).
• EMA +ve (patchy cytoplasmic).
• Smooth muscle actin +ve.

See also

• Neuropathology tumours.