Extrarenal rhabdoid tumours, also known as rhabdoid tumours of soft tissue or malignant rhabdoid tumours are highly malignant neoplasms of uncertain differentiation mainly seen in infants and children.
On this page:
Epidemiology
Extrarenal rhabdoid tumours are very rare and most are found in infants and children 1-3.
Diagnosis
Extrarenal rhabdoid tumours are diagnosed by typical histological features.
Diagnostic criteria
Diagnostic criteria according to the WHO classification of soft tissue tumours (blue book) 1:
cell morphology: rhabdoid or primitive undifferentiated cells
loss of SMARCB1/INI1 expression
Clinical presentation
Clinically the tumours commonly manifest as fast-growing soft tissue masses and symptoms usually depend on the location or organ where they are found, in some cases, they occur as disseminated tumours 1.
Pathology
Extrarenal rhabdoid tumours are highly malignant and have morphologically and genetically identical counterparts in the kidney and brain 1.
Aetiology
About 13% are inherited 1.
Location
Extrarenal rhabdoid tumours are can be found in the deep axial soft tissue locations like the neck, paraspinal and perineal regions the retroperitoneum or the abdominal cavity, they have been also found in the extremities and the skin as well as visceral organs including the liver, thymus, gastrointestinal tract and those of the genitourinary system 1-3.
Macroscopic appearance
Macroscopically extrarenal rhabdoid tumours are unencapsulated soft and of grey to tannish colour 1.
Microscopic appearance
Histologically extrarenal rhabdoid tumours are characterised by the following features 1:
rhabdoid cells with large vesicular nuclei and glassy eosinophilic cytoplasm
intracytoplasmatic hyaline-like inclusion bodies
Immunophenotype
On immunohistochemistry stains, extrarenal rhabdoid tumours often express cytokeratins and epithelial membrane antigen (EMA) as well as synaptophysin and CD99 1.
Genetics
Extrarenal rhabdoid tumours are associated with deletions in chromosome 22q11 or germline mutations of the SMARCB1/INI1 gene 1-3.
Radiographic features
Radiologically extrarenal rhabdoid tumours have been described as lobulated bulky non-specific soft tissue masses that show aggressive features such as bone erosions 2,3.
CT
On CT rhabdoid tumours have been described as consistently hypodense 3.
MRI
On MRI rhabdoid tumours have been shown as lobulated heterogeneous irregular non-specific masses 2-4.
Signal characteristics
T1: heterogeneously iso to hypointense
T2: heterogeneously iso to hyperintense
T1C+ (Gd): heterogeneous enhancement
Radiology report
The radiological report should include a description of the following:
form, location and size
tumour margins and transition zone
relations to the muscular fascia
relation to adjacent neurovascular structures
relations to bones and other organs
Treatment and prognosis
Extrarenal rhabdoid tumours have a grim prognosis with a 5-year survival of < 15% 1.
History and etymology
Malignant rhabdoid tumours were first described in 1978 by the American pathologists John Bruce Beckwith and his colleague Nigel F. Palmer as a rhabdomyosarcomatoid variant of a Wilms tumour and specified as a distinct entity by the Mexican paediatric pathologist Francisco Gonzalez-Crussi and his colleagues in 1982 3,5,6.
Differential diagnosis
Tumours that can mimic the presentation and/or appearance of extrarenal rhabdoid tumours include 2,3:
undifferentiated teratoma
Unable to process the form. Check for errors and try again.