Also known as:NTRK3 FISH, ETV6-NTRK3 FISH, Secretory Breast Carcinoma FISH, Secretory Breast Cancer FISH
Oncology - Breast cancer
Use of test
Secretory carcinoma of the breast is a rare subtype of breast carcinoma, characterised by gene fusions involving NTRK3, particularly with the partner gene ETV6. .
This test has diagnostic, prognostic and potential therapeutic implications. Detection of a gene fusion event involving NTRK3 helps to confirm a potential diagnosis of secretory breast carcinoma, which has a generally favourable prognosis compared with other breast cancers. In addition, TRK inhibitors such as larotrectinib and entrectinib have shown efficacy against tumours with NTRK gene rearrangements. These agents are TGA-listed in Australia, although they are not PBS-funded at the time of writing. (Feb 2021)
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.
Fluorescent in situ hybridisation (FISH) analysis, using a break-apart probe to detect rearrangements involving NTRK3. Note that this does not identify the specific fusion partner, but would be expected to detect ETV6-NTRK3 fusions. 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 of the 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.
Formalin-fixed, paraffin embedded tissue (FFPE) - 15 sections of 4 uM thickness, dried overnight at 37°C onto charged/coated slides.
Please stain the first section with H&E, and label each slide with patient and block identifiers. Label the unstained sections sequentially (slides 2-15). The request should be accompanied by the somatic mutation request form (above) and a copy of the original histopathology report.
Up to 4 weeks.
If more information is required, the requesting clinician can call our laboratory on (07) 3377 8573.
An MBS rebate is available if criteria are met (item number 73379).