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Test ID: APCZ APC Gene, Full Gene Analysis

Useful For

Confirmation of familial adenomatous polyposis (FAP) diagnosis for patients with clinical features

Additional Tests

Test ID Reporting Name Available Separately Always Performed
COLAB Hereditary Colon Cancer CGH Array Yes, (order FMTT) Yes

Testing Algorithm

When this test is ordered, comparative genomic hybridization will always be performed at an additional charge.

 

This test should be ordered only for individuals with symptoms suggestive of familial adenomatous polyposis (FAP). Asymptomatic patients with a family history of FAP should not be tested until a mutation has been identified in an affected family member.

 

See Colonic Polyposis Syndromes Testing Algorithm in Special Instructions.

Method Name

Custom Sequence Capture and Targeted Next-Generation Sequencing

Array comparative genomic hybridization (aCGH) is used to test for the presence of large deletions and duplications.

Reporting Name

APC Gene, Full Gene Analysis

Specimen Type

Varies


Shipping Instructions


Specimen preferred to arrive within 96 hours of draw.



Specimen Required


Specimen Type: Whole blood

Container/Tube:

Preferred: Lavender top (EDTA) or yellow top (ACD)

Acceptable: Any anticoagulant

Specimen Volume: 3 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send specimen in original tube.


Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time
Varies Ambient (preferred)
  Frozen 
  Refrigerated 

Clinical Information

Familial adenomatous polyposis (FAP) is an autosomal dominant condition caused by mutations in the APC gene located on the long arm of chromosome 5 (5q21). Classic FAP is characterized by progressive development of hundreds to thousands of adenomatous colon polyps. Polyps may develop during the first decade of life and the majority of untreated FAP patients will develop colon cancer by age 40. Typically, there is a predominance of polyps on the left side of the colon, however, other areas of the colon may also be affected. The presence of extracolonic manifestations is variable and includes gastric and duodenal polyps, ampullary polyps, osteomas, dental abnormalities (unerupted teeth), congenital hypertrophy of the retinal pigment epithelium (CHRPE), benign cutaneous lesions, desmoids tumors, hepatoblastoma, and extracolonic cancers. Common constellations of colonic and extracolonic manifestations have resulted in the designation of 3 clinical variants: Gardner syndrome, Turcot syndrome, and hereditary desmoid disease.

 

Gardner syndrome is characterized by colonic polyps of classic FAP with epidermoid skin cysts and benign osteoid tumors of the mandible and long bones.

 

Turcot syndrome is characterized by multiple colonic polyps and central nervous system (CNS) tumors. Turcot syndrome is an unusual clinical variant of FAP, as it is also considered a clinical variant of hereditary nonpolyposis colorectal cancer (HNPCC). Individuals with Turcot syndrome have CNS tumors in addition to adenomatous polyps. The types of CNS tumor observed helps to distinguish Turcot-FAP variant patients from Turcot-HNPCC variant patients. The predominant CNS tumor associated with the Turcot-FAP variant is medulloblastoma, while glioblastoma is the predominant CNS tumor associated with Turcot-HNPCC.

 

Hereditary desmoid disease (HDD) is a variant of FAP with multiple desmoids tumors as the predominant feature. Many patients with HDD may not even show colonic manifestations of FAP. APC germline testing may assist clinicians in distinguishing a sporadic desmoid tumor from that associated with FAP.

 

Attenuated FAP (AFAP) is characterized by later onset of disease and a milder phenotype (typically <100 adenomatous polyps and fewer extracolonic manifestations) than classic FAP. Typically individuals with AFAP develop symptoms of the disease at least 10 to 20 years later than classically affected individuals. Individuals with AFAP often lack a family history of colon cancer and/or multiple adenomatous polyps. Of note, clinical overlap is observed between AFAP and MYH-associated polyposis (MAP), an autosomal recessive polyposis syndrome typically associated with fewer than 100 polyps. Although the clinical phenotype of MAP remains somewhat undefined, extracolonic manifestations, including CHRPE have been described in affected patients. Given the phenotypic overlap of AFAP and MAP, these tests are commonly ordered together or in a reflex fashion.

 

See Colonic Polyposis Syndromes Testing Algorithm in Special Instructions for additional information. Also see Hereditary Colorectal Cancer: Adenomatous Polyposis Syndromes (September 2004 Communique) in publications for additional information.

Reference Values

An interpretive report will be provided.

Interpretation

All detected alterations are evaluated according to American College of Medical Genetics recommendations.(1) Variants are classified based on known, predicted, or possible pathogenicity and reported with interpretive comments detailing their potential or known significance.

Clinical Reference

1. Richards S, Aziz N, Bale S, et al: Standards and guidelines for the interpretation of sequence variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology. Genet Med 2015 May;17(5):405-424

2. American Society of Clinical Oncology. American Society of Clinical Oncology policy statement update: genetic testing for cancer susceptibility Clin Oncol. 2003;21:2397-2406

3. Half E, Bercovich D, Rozen P: Familial adenomatous polyposis. Orphanet J Rare Dis. 2009 Oct 12;4:22

4. Croner RS, Brueckl WM, Reingruber B, et al: Age and manifestation related symptoms in familial adenomatous polyposis. BMC Cancer 2005 Mar 2;5:24

Day(s) and Time(s) Performed

Performed weekly; Varies

Analytic Time

14 days

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

81201-APC (adenomatous polyposis coli) (eg, familial adenomatosis polyposis [FAP], attenuated FAP) gene analysis; full gene sequence

81228-Cytogenomic constitutional (genome-wide) microarray analysis; interrogation of genomic regions for copy number variants (eg, bacterial artificial chromosome [BAC] or oligo-based comparative genomic hybridization [CGH] microarray analysis)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
APCZ APC Gene, Full Gene Analysis In Process

 

Result ID Test Result Name Result LOINC Value
53568 Result Summary 50397-9
53569 Result In Process
53570 Interpretation In Process
53571 Additional Information 48767-8
53572 Specimen In Process
53573 Source 31208-2
53574 Array Billed? No LOINC Needed
53575 Released By No LOINC Needed

Forms

1. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (T576) is available in Special Instructions.

2. Molecular Genetics: Inherited Cancer Syndromes Patient Information (T519) in Special Instructions

3. If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:

Oncology Test Request Form (T729) (http://www.mayomedicallaboratories.com/it-mmfiles/oncology-request-form.pdf)

Gastroenterology and Hepatology Test Request Form (T728) (http://www.mayomedicallaboratories.com/it-mmfiles/gastroenterology-and-hepatology-test-request.pdf)

Mayo Medical Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

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