MDM2 Amplification by FISH

Performing Lab:

UCSF Clinical Cancer Genomics Lab

CPT Code:

88377

Specimen Type
Formalin-fixed, paraffin-embedded tissue on six (6) unstained slides (5 microns thick) on charged glass. One adjacent hematoxylin and eosin stained (H&E) slide should also be included. Slides should be labeled with pathology case number and block identification. Cytology smears may also be used for testing if there is sufficient tumor present. Contact the laboratory at 415.502.3252 or [email protected] if testing on a cytology smear is desired.

Methodology: Fluorescence in-situ hybridization (FISH)
Turnaround Time: 7-14 days

TEST INDICATIONS:

MDM2 amplification by FISH is designed to detect amplification of the MDM2 gene to aid in patient diagnosis of soft tissue and bone tumors.

In soft tissue tumors, MDM2 amplification is a frequent and specific finding in well differentiated liposarcoma/atypical lipomatous tumor (ref. 1), and its presence in high grade sarcomas supports dedifferentiated liposarcoma (2).

In bone tumors, MDM2 amplification in a low grade fibrous/fibro-osseous tumor supports low grade osteosarcoma (3), and its presence in high grade osteosarcoma supports progression from a low grade tumor (4).

References:

1. Weaver J et al. Fluorescence in situ hybridization for MDM2 gene amplification as a diagnostic tool in lipomatous neoplasms. Mod Pathol. 2008 Aug;21(8):943-9.

2. Song MJ et al. Application of MDM2 Fluorescence In Situ Hybridization and Immunohistochemistry in Distinguishing Dedifferentiated Liposarcoma From Other High-grade Sarcomas. Appl Immunohistochem Mol Morphol. 2017 Nov/Dec;25(10):712-719.

3. Dujardin F et al. MDM2 and CDK4 immunohistochemistry is a valuable tool in the differential diagnosis of low-grade osteosarcomas and other primary fibro-osseous lesions of the bone. Mod Pathol. 2011 May;24(5):624-37.

4. Yoshida A et al. MDM2 and CDK4 immunohistochemical coexpression in high-grade osteosarcoma: correlation with a dedifferentiated subtype. Am J Surg Pathol. 2012 Mar;36(3):423-31.

HOW THE TEST WORKS:

The MDM2 amplification by FISH assay is designed to identify amplification of the MDM2 locus at 12q15. It utilizes a Vysis(TM) dual-color DNA probe set. The probe set includes the loci-specific identifier (LSI) MDM2 probe that hybridizes to the MDM2 target on chromosome 12q15, producing an orange signal while CEP12 (chromosome 12 centromere probe) serves as a reference probe, producing a green signal. Formalin-fixed, paraffin-embedded tissue on a glass slide is de-paraffinized and then treated with pepsin to digest tissue proteins and allow for probes to reach target DNA. The DNA is then heat denatured and subsequently allowed to hybridize with the probe set. After hybridization, the slide is washed to remove any of the excess unbound probes and the nuclei are counterstained with DAPI (4,6 diamidino-2-phenylidole). Enumeration of the MDM2 and CEP12 signals is conducted by microscopic examination of cell nuclei using a fluorescence microscope equipped with appropriate excitation and emission filters. An H&E slide is reviewed prior to testing.

LIMITATIONS OF THE TEST:

The clinical interpretation of this test should be evaluated within the context of the patient's medical history, other diagnostic tests, and the histologic and immunohistochemical features of the tumor.

MDM2 amplification by FISH was validated by the UCSF Clinical Cancer Genomics Laboratory to confirm performance characteristics, in compliance with current guidelines for clinical implementation. The laboratory is CLIA certified to perform high complexity testing.

SPECIMEN REQUIREMENTS FOR A SUCCESSFUL TEST:

Blocks selected for MDM2 amplification testing must contain tumor tissue. The assay is optimized for formalin-fixed tissue; tissue processed with other fixatives will not be rejected, but may not provide interpretable results. Decalcified specimens are usually unsuitable for FISH testing but an attempt at hybridization will be performed. An adjacent H&E-stained slide must be included. Contact the laboratory at 415.502.3252 or [email protected] if the specimen suitability is uncertain. Label slides with pathology case number and block identification.

Specimen rejection criteria include: All required slides not included. Insufficient tumor tissue present on slide as determined by pathologist. Outside slides not labeled or not accompanied by printed copy of test order.

HOW TO ORDER THE TEST:

UCSF Clinicians — this test can be ordered through Pathology
Outside Physicians — this test can be ordered with the CCGL Requisition Form

For all specimens, an interpretation of this test by a laboratory physician will automatically be performed and billed for separately.