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HelpTest Code MTAP Methylthioadenosine Phosphorylase (MTAP), Diagnostic, Immunostain, Tech Only
Ordering Guidance
This test includes only technical performance of the stain (no pathologist interpretation is performed).
This test is for qualitative immunohistochemistry testing of methylthioadenosine phosphorylase for diagnostic purposes without interpretation.
For predictive immunostain detection of methylthioadenosine phosphorylase expression in solid tumors with interpretation, order MTAPS / Methylthioadenosine Phosphorylase, Solid Tumor, Immunohistochemistry.
For interpretation and diagnosis of submitted pathology specimens with appropriate additional stains and other ancillary testing, order PATHC / Pathology Consultation.
Additional material may be needed if alternative testing is requested. See the specific specimen requirements for any alternative requested testing.
Shipping Instructions
Attach the green "Attention Pathology" address label (T498) and the pink Immunostain Technical Only label included in the kit to the outside of the transport container.
Specimen Required
Specimen Type: Tissue
Supplies: Immunostain Technical Only Envelope (T693)
Container/Tube: Immunostain Technical Only Envelope
Submit:
Formalin-fixed, paraffin-embedded tissue block
OR
2 Unstained, positively charged glass slides (25- x 75- x 1-mm) per test ordered; sections 4-microns thick
Forms
If not ordering electronically, complete, print, and send an Immunohistochemical (IHC)/In Situ Hybridization (ISH) Stains Request (T763) with the specimen.
Useful For
Qualitative detection of methylthioadenosine phosphorylase (MTAP) in a diagnostic setting
Aiding in the diagnosis of mesothelioma
This test should not be used to predict response to treatment.
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| IHTOI | IHC Initial, Tech Only | No | No |
| IHTOA | IHC Additional, Tech Only | No | No |
Method Name
Immunohistochemistry (IHC)
Reporting Name
MTAP IHC, Tech OnlySpecimen Type
TECHONLYSpecimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| TECHONLY | Ambient (preferred) | |
| Refrigerated | ||
Reject Due To
| Wet/frozen tissue | Reject |
| Cytology smears | Reject |
| Nonformalin fixed tissue | Reject |
| Nonparaffin embedded tissue | Reject |
| Noncharged slides | Reject |
| ProbeOn slides | Reject |
| Snowcoat slides | Reject |
Clinical Information
Methylthioadenosine phosphorylase (MTAP) is a chromosome 9p21.3 related protein involved in purine metabolism that plays a role in salvage of adenosine and methionine and is expressed in mesothelial cells. Loss of expression of MTAP protein is a reliable marker for malignancy in mesothelial proliferations and may also occur in a subset of carcinomas.
Interpretation
This test does not include pathologist interpretation, only technical performance of the stain. If interpretation is required, order PATHC / Pathology Consultation for a full diagnostic evaluation or second opinion of the case.
The positive and negative controls are verified as showing appropriate immunoreactivity.
Interpretation of this test should be performed in the context of the patient's clinical history and other diagnostic tests by a qualified pathologist.
Cautions
Age of a cut paraffin section can affect immunoreactivity. Stability thresholds vary widely among published literature and are antigen dependent. Best practice is for paraffin sections to be cut within 6 weeks.
Recommended fixation time is between 6 and 48 hours.
This assay has not been validated on tissues subjected to the decalcification process or use of alternative fixatives for bone and bone marrow specimens or cell blocks.
The charge of glass slides can be affected by environmental factors and subsequently may alter slide staining. Sending unsuitable glass slides can result in inconsistent staining due to poor slide surface chemistry.
Best practices for storage of positively charged slides:
-Minimize time slides are stored after being unpackaged
-Limit exposure to high humidity and heat
-Minimize exposure to plastics
Clinical Reference
1. Berg K, Dacic S, Miller C, et al. Utility of methylthioadenosine phosphorylase compared With BAP1 immunohistochemistry, and CDKN2A and NF2 fluorescence in situ hybridization in separating reactive mesothelian proliferations from epithelioid malignant mesotheliomas. Arch Pathol Lab Med. 2018;1-5
2. Hida T, Hamasaki M, Matsumoto S, et al. Immunohistochemical detection of MTAP and BAP1 protein loss for mesothelioma diagnosis: Comparison with 9p21 FISH and BAP1 immunohistochemistry. Lung Cancer. 2017;104(12):98-105
3. Su C, Chang Y, Chan Y, et al. MTAP is an independent prognosis marker and the concordant loss of MTAP and p16 expression predicts short survival in non-small cell lung cancer patients. EJSO. 2014;40(6):1143-1150
4. Watanabe F, Takao M, Inoue K, et al: Immunohistochemical diagnosis of methylthioadenosine phosphorylase (MTAP) deficiency in non-small cell lung carcinoma. Lung Cancer. 2009;63(4):39-44
5. Magaki S, Hojat SA, Wei B, So A, Yong WH. An Introduction to the Performance of Immunohistochemistry. Methods Mol Biol. 2019;1897:289-298. doi:10.1007/978-1-4939-8935-5_25
Day(s) Performed
Monday through Friday
Report Available
1 to 3 daysSpecimen Retention Time
Until staining is completedPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.CPT Code Information
88342-TC, primary
88341-TC, if additional IHC
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| MTAP | MTAP IHC, Tech Only | Order only;no result |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 605178 | MTAP IHC, Tech Only | Bill only; no result |
Testing Algorithm
For the initial technical component only immunohistochemical (IHC) stain performed, the appropriate bill-only test ID will be reflexed and charged (IHTOI). For each additional technical component only IHC stain performed, an additional bill-only test ID will be reflexed and charged (IHTOA).