GNAQ Mutation Testing

Performing Lab:

UCSF Clinical Cancer Genomics Lab

CPT Code:

81403, 88381

Specimen Type: Formalin-fixed, paraffin-embedded tissue. Tissue block or unstained slides. If sending unstained slides, we require five (5) 10-micron tissue sections on uncharged glass slides. One adjacent H&E stained slide should be included. 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: Sanger sequencing
Turnaround Time: 7-14 days

TEST INDICATIONS:

A variety of benign and malignant melanocytic neoplasms have been described to harbor mutations in either codon 183 or 209 of GNAQ including uveal nevi and melanoma, blue nevi, and primary CNS melanocytomas and melanomas. GNAQ mutations at codon 209 are found in 46% of primary uveal melanoma and 22% of uveal melanoma metastases.

HOW THE TEST WORKS:

A histologic section of formalin-fixed, paraffin-embedded tissue is examined by a pathologist to identify areas of tumor. DNA is extracted from these areas and regions of GNAQ exons 4 and 5 including codons 183 and 209 are captured and sequenced by next generation sequencing.

LIMITATIONS OF THE TEST:

Results of this test should be correlated with the patient’s other clinical and laboratory information. This assay only detects mutations in exons 4 and 5 of GNAQ (including codons 183 and 209).

This test was validated by the UCSF Clinical Cancer Genomics Laboratory to confirm performance characteristics, in compliance with current guidelines for clinical implementation.

SPECIMEN REQUIREMENTS FOR A SUCCESSFUL TEST:

In general, the tumor should be a minimum of 0.4 cm in size. Blocks selected for GNAQ Mutation Testing must contain tumor tissue. Areas of tumor must contain at least 50% tumor cells. The lab can remove adjacent non-tumor tissue, so the entire slide does not need 50% tumor cells, just the area with tumor. 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 APeX
Outside Physicians — this test can be ordered using the CCGL Requisition Form

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