Solid alveolar rhabdomyosarcoma of the thorax in a child.
OBJECTIVE
This case illustrates the difficulties and pitfalls of diagnosis of alveolar rhabdomyosarcoma in its solid variant and in an unusual primary location, the mediastinum.


METHODS
A 9-year-old boy presented with a primary thoracic tumour associated with metastasis in the left sacroiliac joint. Bronchial and mediastinal biopsies showed a malignant neoplasm with a solid sheet-like pattern of small round cells with a high nuclear to cytoplasmic ratio associated with little or no fibrosis usually evocative of a peripheral neuroectodermal tumour (PNET) at this age. Immunohistochemical positive staining with vimentin (80% of tumour cells), desmin (20%) and titin (30%) antibodies was suggestive of a rhabdomyosarcoma. In addition, all neural cell adhesion molecule (NCAM) markers tested were positive as well as MIC2, a marker for the Ewing family of sarcomas. There was no rhabdomyoid differentiation at ultrastructural examination. Molecular analysis with RT-PCR amplification of RNA isolated from the tumour demonstrated the presence of a PAX3/FKHR fusion transcript, product of a t(2;13) reciprocal translocation, a genetic marker specific for alveolar rhabdomyosarcoma.


CONCLUSIONS
The diagnostic methodology of a small round cell tumour of the child must now include immunohistochemical study and molecular biology to confirm the diagnosis of alveolar rhabdomyosarcoma, in a solid and undifferentiated variant.
Sartelet
H
H
Laboratoire de Pathologie Cellulaire, CHRU Grenoble, France.
Lantuejoul
S
S
Armari-Alla
C
C
Pin
I
I
Delattre
O
O
Brambilla
E
E
D001984:Bronchial Neoplasms / Q000235:genetics / Q000276:immunology / Q000473:pathology*; D002648:Child; D005819:Genetic Markers; D006801:Humans; D007150:Immunohistochemistry; D016130:Immunophenotyping; D008297:Male; D008479:Mediastinal Neoplasms / Q000235:genetics / Q000276:immunology / Q000473:pathology*; D016133:Polymerase Chain Reaction; D018232:Rhabdomyosarcoma, Alveolar / Q000235:genetics / Q000276:immunology / Q000473:pathology*
D005819:Genetic Markers