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Test Code APC S+D/D Familial Adenomatous Polyposis (FAP) APC Gene Sequencing and Del/Dup

Important Note

This test includes concurrent APC sequencing and deletion/duplication testing. Please order a MISC test for sequencing only or deletion/duplication only.

Clinical System Name

APC Gene Sequencing and Del/Dup

Synonyms

Gardner syndrome

Turcot syndrome

Attenuated FAP

FAP

FAP Gene Sequencing and Del/Dup

Description

FAP (familial adenomatous polyposis) is a colon cancer predisposition syndrome in which hundreds to thousands of precancerous colonic polyps develop, beginning, on average, at age 16 years (range 7-36 years). By age 35 years, 95% of individuals with FAP have polyps; without colectomy, colon cancer is inevitable. The mean age of colon cancer diagnosis in untreated individuals is 39 years (range 34-43 years). Extracolonic manifestations are variably present and include: polyps of the gastric fundus and duodenum, osteomas, dental anomalies, congenital hypertrophy of the retinal pigment epithelium (CHRPE), soft tissue tumors, desmoid tumors, and associated cancers.

 

Attenuated FAP is characterized by a significant risk for colon cancer but fewer colonic polyps (average of 30), more proximally located polyps, and diagnosis of colon cancer at a later age; management may be substantially different.

 

Gardner syndrome is characterized by colonic polyposis typical of FAP together with osteomas and soft tissue tumors.

 

Turcot syndrome is the association of colonic polyposis and central nervous system (CNS) tumors.

Differences in phenotype may relate to the location of the pathogenic variant within APC.

Sample Requirements

Specimen: Whole Blood

Container(s): Lavender Top/EDTA, Yellow/ACD

Preferred Vol: 3 - 5 mL

Minimum Vol: 1 mL for small infants

 

Specimen: DNA

Container(s): Sterile plastic tube

Preferred Vol: 10µg -15 µg of purified DNA at a concentration of at least 20 µg/ml for NGS and Sanger tests and at least 5 µg of purified DNA at a concentration of at least 100 µg/ml for gene-centric aCGH, MLPA, and CMA

 

Processing Instructions

Reject due to:

Spin: N

Aliquot: N

Temp: 2-8 C

Storage location: Deliver blood to Sendouts refrigerator rack. Store labels in the clear plastic box on front of the CPA fridge.

 

Off-site collection: Send whole blood refrigerated.

Stability

Specimen Type Temperature Time
Whole blood Room temp 3 d
Whole blood Refrigerated 7 d
Whole blood Frozen N
Extracted DNA Room temp 3-4 d
Extracted DNA Refrigerated 1 y
Extracted DNA Frozen Indefinitely

 

Availability

STAT TAT
N 4 w

 

Performing Laboratory

PreventionGenetics 

Department

Department:     PreventionGenetics, 3800 S. Business Park Ave., Marshfield, Wisconsin 54449

Phone Number:    (715) 387-0484

 

Reference Range

Interpretive report is provided.

Methodology

Method: NextGen sequencing with Sanger sequencing supplemented as needed and deletion/duplication testing via aCGH.

Analytical Volume:

Limitations:

Clinical sensitivity: This test is predicted to detect >90% of causative FAP mutations (Laken et al. PNAS 96:2322-2326, 1999).

Special Instructions

Links to:

 

PreventionGenetics

 

Sample details, PreventionGenetics

 

Clinical Utility

Molecular genetic testing of APC detects pathogenic variants in up to 90% of individuals with typical FAP. Molecular genetic testing is most often used in the early diagnosis of at-risk family members, as well as in confirming the diagnosis of FAP or attenuated FAP in individuals with equivocal findings (e.g., <100 adenomatous polyps).

 

GeneReviews:  APC-Associated Polyposis Conditions

Send Out Instructions

Reference Test Name: Familial Adenomatous Polyposis via APC Gene Sequencing with CNV detection
Test Code: 3115
Instructions: Ship whole blood overnight, ambient temperature. PreventionGenetics accepts Saturday delivery