ARUP's Laboratory Test Directory
| 0051740: HNPCC/Lynch Syndrome, Microsatellite Instability by PCR |
| Test Mnemonic: MSI PCR | |
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Methodology: Polymerase Chain Reaction/Fragment Analysis
Performed: Mon-Fri Reported: Within 14 days |
| Specimen Required: | |
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Collect: Tumor and normal tissue from colon. Note: Surgical resections are usually the best source for this material. Individuals with rectal cancer often receive chemoradiation before surgical resection, often resulting in minimal residual tumor. In such cases, the pre-treatment biopsy is usually a better source for tumor tissue. The post-treatment resection can still be used for the normal specimen. Transport: Paraffin-embedded, formalin-fixed two to three tumor and one normal tissue blocks at 20-25°C. Ship in cooled container during summer months. Include surgical pathology report. Unacceptable Conditions: Paraffin block with no tumor tissue remaining; specimens fixed in formalin substitute. Stability: Ambient: Indefinitely; Refrigerated: Indefinitely; Frozen: Unacceptable |
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| Interpretive Data: | |
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Samples from a tumor specimen and normal tissue are amplified by PCR for the five microsatellite markers: BAT-25, BAT-26, MONO-27, NR-21, and NR-24. Fluorescently labeled products are detected and sized by capillary electrophoresis. Patterns of normal and tumor genotypes are compared for each marker and scored as stable or unstable. Microsatellite instability (MSI)-High indicates a tumor with instability in two or more mononucleotide microsatellite repeats. MSI-High occurs in approximately 90% of colorectal cancers from individuals with Lynch syndrome, also known as hereditary nonpolyposis colorectal cancer (HNPCC), and in 10-15% of sporadic colon cancer. MSI-Indeterminate indicates a tumor with instability in one of five mononucleotide microsatellite repeats. Since instability in even a single mononucleotide marker can be indicative of a mismatch repeat deficient tumor, we recommend that these results be analyzed in concert with immunohistochemical (IHC) staining for mismatch repair genes (test 0049302). MSI-Stable indicates a lack of microsatellite instability in a tumor. A lack of microsatellite instability would be unusual in colorectal cancers from individuals with Lynch syndrome (HNPCC), although it does not completely exclude this possibility Evaluation of microsatellite instability with Microsatellite Instability/HNPCC by Immunohistochemical Stain (0049302) may be helpful in this determination. This interpretation may not apply to tumors other than colon cancers. The lack of microsatellite instability does not rule out the possibility of other colon cancer-associated genetic disorders. Please correlate with clinical findings. Genetic counseling is recommended. This test is performed pursuant to an agreement with Roche Molecular Systems, Inc. Please refer to Statement B in the Compliance Statements section in the front of the Laboratory Test Directory. |
| CPT Code(s): | |
| 83907 x2 Lysis; 83890 x2 Isolation; 83898 x7 Amplification; 83909 Capillary electrophoresis; 83912 Interpretation and report - Additional CPT code modifiers may be required for procedures performed to test for oncologic or inherited disorders. |