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Test Code MTAP Methylthioadenosine Phosphorylase (MTAP) Immunostain, Tech Only


Ordering Guidance


This test includes only technical performance of the stain (no pathologist interpretation is performed). If diagnostic consultation by a pathologist is required order PATHC / Pathology Consultation.



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

Preferred:

-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

Acceptable: None


Forms

If not ordering electronically, complete, print, and send an Immunohistochemical (IHC)/In Situ Hybridization (ISH) Stains Request (T763) with the specimen.

Secondary ID

605177

Useful For

Aiding in the diagnosis of malignant mesothelioma

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 Only

Specimen Type

TECHONLY

Specimen Stability Information

Specimen Type Temperature Time Special Container
TECHONLY Ambient (preferred)
  Refrigerated 

Reject Due To

Wet/frozen tissue 
Cytology smears 
Nonformalin fixed tissue 
Nonparaffin embedded tissue 
Noncharged slides 
ProbeOn slides 
Snowcoat slides 		 Reject 

Clinical Information

Methylthioadenosine phosphorylase (MTAP) is a 9p21.3 related protein involved in purine metabolism that plays a role in salvage of adenosine and methionine and is expressed in mesothelial cells. Deletion of the 9p21.3 chromosome region and loss of MTAP (or BCRA1 associated protein 1: BAP1) protein expression is a reliable marker for malignant mesothelioma diagnosis.

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. If a control tissue is not included on the slide, a scanned image of the relevant quality control tissue is available upon request; call 855-516-8404.

 

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 methylthiodenosine 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

Method Description

Immunohistochemistry on sections of paraffin-embedded tissue.(Unpublished Mayo method)

Day(s) Performed

Monday through Friday 

Report Available

1 to 3 days

Specimen Retention Time

Until staining is completed

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

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

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).