| Interpretive Data: |
Background Information for Familial Adenomatous Polyposis Panel: (APC) Sequencing and Deletion/Duplication, (MUTYH) 2 Mutations:
Characteristics of APC-associated Polyposis: Familial Adenomatous Polyposis (FAP): Development of hundreds to thousands of adenomatous colonic polyps beginning in early adolescence; lifetime risk for cancer is 100 percent. Additional findings may include dental anomalies, polyps of the gastric fundus and duodenum, and congenital hypertrophy of the retinal pigment epithelium (CHRPE).
Attenuated FAP: Fewer colonic adenomatous polyps (average of 30), which are more proximally located and cancer generally occurs at a later age; lifetime risk for cancer is 70 percent.
Gardner syndrome: Multiple colonic adenomatous polyps along with osteomas, desmoid tumors, and soft tissue tumors.
Incidence: Less than 1 percent of colorectal cancer cases.
Inheritance: Autosomal dominant.
Penetrance: Greater than 99 percent in untreated individuals.
Causes: Pathogenic APC gene mutations.
Clinical Sensitivity: Approximately 95 percent for classic FAP and less than 30 percent for attenuated FAP.
Methodology: Bidirectional sequencing of the APC coding region and intron-exon boundaries. Multiplex ligation-dependent probe amplification (MLPA) to detect large APC coding region deletions or duplications.
Analytical Sensitivity and Specificity: 99 percent.
Limitations: Rare diagnostic errors can occur due to primer or probe site mutations. APC regulatory region and deep intronic mutations will not be detected. Deletion/duplication breakpoints will not be determined.
Characteristics of MUTYH-associated Polyposis (MAP): Development of colonic polyps (10-100) with the age of diagnosis occurring in the third decade or older.
Incidence: Less than 1 percent of colorectal cancer cases.
Inheritance: Autosomal recessive.
Penetrance: Greater than 99 percent in untreated individuals.
Causes: Pathogenic biallelic MUTYH gene mutations.
Clinical Sensitivity: 85 percent of MUTYH mutations in Caucasians.
Methodology: Targeted testing for the MUTYH mutations c.494A>G(Y165C) and c.1145G>A (G382D) by PCR and bidirectional sequencing.
Analytical Sensitivity and Specificity: 99 percent.
Limitations: Rare diagnostic errors can occur due to primer site mutations. Mutations in the MUTYH gene, other than Y165C and G382D, are not evaluated.
Counseling and informed consent are recommended for genetic testing. Consent forms are available online at www.aruplab.com.
Refer to Statement C under Testing Information at http://www.aruplab.com.
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| CPT Code(s): |
Sequencing (APC and MUTYH): 83891 Isolation; 83898 x42 Amplification; 83904 x42 Sequencing; 83909 Capillary electrophoresis. Del/Dup: 83896 x17 Nucleic acid probes; 83898 x17 Amplification; 83914 x17 Extension; 83909 Capillary electrophoresis; 83912 Interpretation and report - Additional CPT code modifiers may be required for procedures performed to test for oncologic or inherited disorders.
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Cross References: |
APC-Associated Polyposis (Familial Adenomatous Polyposis Panel: APC Sequencing, APC Deletion/Duplication, and MYH 2 Mutations)
, Attenuated FAP (Familial Adenomatous Polyposis Panel: APC Sequencing, APC Deletion/Duplication, and MYH 2 Mutations)
, Gardner Syndrome (Familial Adenomatous Polyposis Panel: APC Sequencing, APC Deletion/Duplication, and MYH 2 Mutations)
, Turcot Syndrome (Familial Adenomatous Polyposis Panel: APC Sequencing, APC Deletion/Duplication, and MYH 2 Mutations)
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