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GNAS Mutational Analysis

Indication

The GNAS gene is mutated, over-expressed and/or amplified in number of diseases including McCune Albright syndrome, thyroid and parathytoid tumors, adrenocortical lesions, pituitary tumors, renal tumors and, rare cases of tumors arising from autonomic ganglia, large intestine, lung and testis. GNAS mutation hotspots are codon 201 in exon 8 and/or codon 227 in exon 9.

Clinically, GNAS mutations can provide evidence of an oncogenic molecular abnormality in appropriate clinicopathologic settings. Also, GNAS mutation in pituitary neoplasms is implicated in increased octreotide (somatostatin agonist) sensitivity in some studies. Understanding the GNAS mutational status at the individual patient level will enable targeted drug testing and further facilitate the advancement of personalized treatment.

Methodology

Mutations are tested using PCR-based bi-directional DNA sequencing (Sanger sequencing) or available on the Solid Tumor Next Gen Sequencing assay (CMS46).

Test Parameters

For Sanger sequencing assay, Exons 8 and 9 are sequenced in their entirety to detect mutations in codons 201 (exon 8) and 227 (exon 9) of GNAS. The lower limit of detection is approximately one cell bearing the mutation per five cells (20%).  For the CMS46 assay, Exon 8, codon 201 is sequenced.

Turnaround Time

10 days

Sample Requirements

Formalin-fixed, paraffin embedded tissue blocks or 10 unstained slides containing adequate amounts of tumor to be analyzed (see above sensitivity), with areas to be tested clearly indicated on the slides/block. Comparison of normal and tumor, or several different areas of tumor can be done, for an additional charge. Please provide a copy of the corresponding pathology report.

CPT Codes

81479

Additional charges may apply for tissue extraction.

The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.


© 2014 The University of Texas MD Anderson Cancer Center