Malignant rhabdoid tumour

Definition

A highly aggressive malignant tumour, most commonly found in the kidney abut also at extra-renal sites, usually arising in infancy but also to be found in adults, characterised by the presence of rhabdoid cells.

Atypical teratoid/rhabdoid tumour occurs in the CNS in infancy. It is usually infratentorial. Most cases show admixture of rhabdoid cells with areas of typical PNET2.

Histopathology

A solid pattern is most common, but the architecture may be trabecular, pseudo-alveolar or myxoid.

The characteristic rhabdoid cells are large and polygonal, with globular juxtanuclear eosinophilic cytoplasmic inclusions, vesicular nuclei and often a single large nucleolus.

Immunohistochemistry

The immunophenotype is variable.

	Vimentin	positive
	EMA	positive
	Cytokeratins	positive
	NSE	variable
	S-100	variable
	CD57 (Leu7)	variable
	CD99	sporadic
	Desmin	sporadic
	INI1	negative: most other tumours are positive

Cytogenetics

There is commonly a deletion of chromosome 22q11.2, the site of the INI1 tumour suppressor gene. There is usually homozygous inactivation of this gene: some patients have a germline mutation. CNS rhabdoid tumours tend to show monosomy for chromosome 222.

Differential diagnosis

Epithelioid sarcoma
Rhabdomyosarcoma with rhabdoid-like inclusions

CNS atypical teratoid/rhabdoid tumour:

PNET
choroid plexus carcinoma

Prognosis

These are aggressive tumours with a poor prognosis.

References

1Hoot, A. C., P. Russo, et al. (2004). "Immunohistochemical analysis of hSNF5/INI1 distinguishes renal and extra-renal malignant rhabdoid tumors from other pediatric soft tissue tumors." Am J Surg Pathol 28(11): 1485-91.

2Judkins, A. R., J. Mauger, et al. (2004). "Immunohistochemical analysis of hSNF5/INI1 in pediatric CNS neoplasms." Am J Surg Pathol 28(5): 644-50.

This page last revised 4.1.2005.