What are the other Names for this Test? (Equivalent Terms)
- Gene Mutation Analysis for Turcot Syndrome
- Test for Molecular Diagnosis of Turcot Syndrome
What is Molecular Testing for Turcot Syndrome? (Background Information)
- Molecular Testing for Turcot Syndrome is a genetic test that is helpful in the diagnosis of this disorder. The lab test results may also be subsequently useful in taking appropriate treatment decisions
- Turcot syndrome is a rare genetic disorder that is characterized by non-cancerous growths (or polyps) in the gastrointestinal tract. Even though the polyps may be initially benign, some tumors may transform into cancer over time. Also, the number of polyps in the colon may increase with time
- Primary tumors can also occur in the brain simultaneously. The types of brain tumor commonly observed in Turcot syndrome are glioblastoma and medulloblastoma
- Since the condition is so rare, the diagnosis may often be delayed in an affected individual
Turcot syndrome is caused by genetic mutations.
- Currently, studies indicate that mutations in APC, MLH1 or PMS2 genes cause the syndrome
- In such cases, molecular gene testing may be helpful in confirming the initial diagnosis
A positive or negative test result should always be interpreted in the context of the individual’s overall signs and symptoms.
The molecular testing, in general, can be performed using a variety of methods. Some of these methods include:
- In situ hybridization techniques, such as fluorescence in situ hybridization (FISH)
- Immunohistochemistry (IHC)
- Next-generation sequencing (NGS)
- Polymerase chain reaction (PCR)
- Comparative genomic hybridization (CGH)
- Karyotyping including spectral karyotyping
- mRNA analysis
- Tissue microarrays (TMAs)
- Southern blot test
- Northern blot test
- Western blot test
- Eastern blot test
The methodology used for Turcot syndrome may vary from one laboratory to another.
Note: Molecular testing has limitations due to the molecular method and genetic mutational abnormalities being tested. This can affect the results on a case-by-case basis. Consultation with your healthcare provider will help in determining the right test and right molecular method, based on individual circumstances.
What are the Clinical Indications for performing the Molecular Testing for Turcot Syndrome?
Molecular Testing for Turcot Syndrome is undertaken in the following situations:
- To assist (and in some cases, confirm) the initial diagnosis of Turcot syndrome
- If there is a family history of the disorder
- To distinguish other conditions that have similar features (signs and symptoms)
- To help in determining treatment options
- To confirm recurrence of the tumor: Tumor recurrence can either be at the original tumor site, or at a distant location (away from the initial site)
How is the Specimen Collected for Molecular Testing for Turcot Syndrome?
The type and source and specimen sample requirements will depend on the preference of the individuals and the preference of the testing lab. Thus, it may vary from one individual to another and from one lab to another. Therefore, it is important to contact the testing lab for exact specimen requirements, before initiating the collecting and testing process.
Following is the specimen collection process for Molecular Testing for Turcot Syndrome:
- Sample on which the test is performed may include:
- Peripheral blood in individuals showing signs and symptoms suspected of Turcot syndrome
- Bone marrow biopsy specimen
- For mitochondrial DNA testing, usually a muscle biopsy or a liver biopsy is preferred
- In case of expectant mothers, prenatal testing through amniotic fluid and chorionic villi sampling
- Fetal cord blood
- Fresh tissue from biopsy
- Fresh tissue from autopsy sample
- Fresh tissue from fetal demise
- Buccal brushes: Using the kit that is provided by the testing laboratory, buccal brushes can be used to collect the specimen, by scraping the inner cheek lining (buccal mucosa)
- Oral rinse specimens
- Body fluids such as saliva, tears, and semen
- Dried blood spots: This specimen type is usually requested in situations where the collection and/or shipping of whole blood is not practical
- In some cases, hair samples (with attached roots), finger nails, and buccal swabs, may be acceptable
- Formalin-fixed paraffin-embedded solid tumor tissue (FFPE tumor tissue), often referred to as paraffin block of the tumor
- Products of conception sample from aborted pregnancy
- Process of obtaining the sample: As outlined by the laboratory testing facility
- Preparation required: As outlined by the laboratory testing facility
Limitations of specimen while testing for Turcot syndrome
- For blood specimens: Individuals, who have received platelet transfusions, red blood transfusion, or white blood (leukocyte) transfusion, should wait at least 4 weeks before providing a blood specimen
- The following specimens may not be acceptable in individuals who have received heterologous bone marrow transplant (in the past):
- Peripheral blood samples
- Oral rinse specimens
- Bone marrow biopsy specimens
- Testing for Turcot syndrome should not be performed on a transplanted organ/specimen, since the genetic material belongs to the donor and not to the individual being tested
- Formalin-fixed paraffin-embedded solid tumor tissue: In many cases, FFPE tissue blocks are usually not acceptable. Please contact the testing lab to ascertain, if it is an acceptable sample specime
- In some cases, a different source of specimen may be acceptable to the laboratory performing the test
Occasionally, additional samples may be required to either repeat the test or to perform follow-up testing.
Turnaround time for test results
- Depending on the location of testing, it may take from 2 to 8 weeks from the time of sample collection, to obtain the test results
Sample storage information
- Many hospitals preserve the paraffin blocks for at least 7 years. In general, older paraffin blocks (over 5 years) may affect the detection of specific mutations, due to degradation of the tissue specimen over time
Cost of Molecular Testing for Turcot Syndrome:
- The cost of the test procedure depends on a variety of factors, such as the type of your health insurance, annual deductibles, co-pay requirements, out-of-network and in-network of your healthcare providers and healthcare facilities
- In many cases, an estimate may be provided before the test is conducted. The final amount may depend upon the findings during the test procedure and post-operative care that is necessary (if any)
What is the Significance of the Molecular Testing for Turcot Syndrome Result?
The significance of Molecular Testing for Turcot Syndrome is explained:
- Presence of a positive test result helps aid, and in some cases, confirm the diagnosis of Turcot syndrome
- The result can help exclude other tumors with similar histological features, or help eliminate other conditions presenting similar signs and symptoms
- It can help determine the prognosis of the patient
- Help in management of the condition following birth of the child
- In some cases, the test results may help in taking treatment decisions
- Individuals showing a positive test result during pregnancy may benefit from genetic counseling
- If there is a family history of the condition, then genetic counseling may be required to help assess the risk, before planning for a child
The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.
Additional and Relevant Useful Information:
- Many laboratories may not have the capability to perform this test. Only highly-specialized labs with advanced facilities and testing procedures may perform this test
- Additional mutations are still being discovered in many of these tumors. This may further contribute towards tumor diagnosis and treatment. Please consult with your healthcare provider for any information updates
Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider of the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.
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