Sorted By Test Name - Mayo Medical Laboratories

83363
fluorescence in situ hybridization (FISH) testing has proven to be useful in identifying the 22q12 EWSR1
gene rearrangement in these tumors.
Useful For: As an aid in the diagnosis of Ewing sarcoma (EWS)/primitive neuroectodermal tumor
(PNET), myxoid chondrosarcoma, desmoplastic small, round cell tumor, clear cell sarcoma, and myxoid
liposarcoma by detecting a neoplastic clone associated with the rearrangement of EWS
Interpretation: A neoplastic clone is detected when the percent of cells with an abnormality exceeds
the normal cutoff for the EWS FISH probe. A positive result is consistent with a diagnosis of Ewing
sarcoma (EWS)/primitive neuroectodermal tumors (PNET). A negative result suggests no rearrangement
of the EWSR1 gene region at 22q12. However, this result does not exclude the diagnosis or EWS/PNET.
Reference Values:
An interpretive report will be provided.
Clinical References: 1. Burchill SA: Ewingâ€s sarcoma: diagnostic, prognostic, and therapeutic
implications of molecular abnormalities. J Clin Pathol 2003 February;56(2):96-102 2. Riley RD, Burchill
SA, Abrams KR, et al: A systematic review of molecular and biological markers in tumors of the
Ewingâ€s sarcoma family. Eur J Cancer 2003 January;39:19-30
Ewing Sarcoma/Primitive Neuroectodermal Tumors (ES/PNET)
by Reverse Transcriptase PCR (RT-PCR), Paraffin
Clinical Information: Ewing sarcoma (ES) and primitive neuroectodermal tumor (PNET), a closely
related tumor, are members of the small-round-cell tumor group that also includes rhabdomyosarcoma,
synovial sarcoma, lymphoma, Wilms tumor, and desmoplastic small round cell tumor. ES is the second
most common malignant tumor of bone in children and young adults. It is an aggressive osteolytic tumor
with a high risk of metastasizing. ES can also present as a soft tissue tumor mass. These tumors are
usually bland and undifferentiated with relatively low mitotic indexes, which is misleading in light of the
rapid growth commonly observed clinically. While treatment and prognosis depend on establishing the
correct diagnosis, the diagnosis of sarcomas that form the small-round-cell tumor group can be very
difficult by light microscopic examination alone, especially true when only small needle biopsy
specimens are available for examination. The use of histochemical and immunohistochemical stains (eg,
MIC2 [CD99], desmin, myogenin, myoD1, WT1) can assist in establishing the correct diagnosis, but
these markers are not entirely specific for ES/PNET. Expertise in soft tissue and bone pathology are often
needed. Studies have shown that some sarcomas have specific recurrent chromosomal translocations.
These translocations produce highly specific gene fusions that help define and characterize subtypes of
sarcomas that are useful in the diagnosis of these lesions.(1-4) The balanced t(11;22)(q24;q12)
chromosomal translocation produces the EWS-FLI-1 fusion transcript and is present in 95% of ES and
PNET. Because the EWS-FLI-1 fusion transcript is a common finding in Ewing sarcoma and PNET, in
soft tissues these 2 lesions are essentially identical. Less common are the t(21;22)(p22;q12) or EWS-ERG
transcript, present in