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Synovial sarcoma FISH

Also known as: t(X;18) FISH, SS18 FISH

Test category:

Oncology - Sarcoma

Use of test

Purpose:

The t(X;18) translocation results in fusion of the SS18 gene on chromosome 18 with one of three related genes on the short arm of the X. The probe determines breakage of SS18. This test has diagnostic implications.

Utility:

The rearrangement is specific for synovial sarcoma, and occurs in around 80% of these tumours.

Ethical considerations:

This is an assay for non-heritable mutations. It does not raise issues of ethics or consent that are different from most other investigations ordered in the routine care of a patient.

Methodology:

Fluorescent in situ hybridisation (FISH) analysis, using probes to detect gene fusions involving the SS18 gene. This test is performed on thin sections of tissue, so some cells in the section may be sliced by the process, and only contain some regions of interest. Sections may contain bony, fatty or necrotic material, which may interfere with processing and/or analysis. Dense tissue also makes identification of individual cells difficult. The accuracy of the results is dependent on the correct identification of tumour on the sections provided, and the assumption that positive results will be identified by a large proportion of cells within the tumour having a rearrangement.

Requesting the test

Ordering:

This test is usually requested by an oncologist.

Request form:

Download the solid tumour somatic mutation request form.

Sample required:

Formalin-fixed, paraffin embedded tissue (FFPE) - 15 sections of 4 uM thickness, dried overnight at 37°C onto charged/coated slides.

Special instructions:

Please label each slide with patient and block identifiers plus number them sequentially 1-15. Stain slides 1 and 15 with H&E and leave slides 2-14 unstained. The request should be accompanied by the somatic mutation request form (above) and a copy of the original histopathology report.

Turnaround time:

Up to 4 weeks.

Price:

This test has a Medicare rebate which, subject to the requirements of the Medicare descriptor being met, may cover all or part of the cost. If the patient is not eligible for rebated testing, please contact your local Sonic pathology practice for pricing.

Rebate:

The Medicare details, including descriptor and schedule fee, are listed under MBS item 73374.

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