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Test ID CTSK Cathepsin K Immunostain, Technical Component 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 pathology address label and the pink Immunostain Technical Only label included in the kit to the outside of the transport container.

Specimen Required

Supplies: Immunostain Technical Only Envelope (T693)

Specimen Type: Tissue

Container/Tube: Immunostain Technical Only Envelope

Preferred: 2 Unstained positively charged glass slide (25- x 75- x 1-mm) per test ordered; sections 4-microns thick

Acceptable: Formalin-fixed, paraffin-embedded (FFPE) tissue block

Useful For

A marker of myeloid lineage

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
IHTOI IHC Initial, Tech Only No No
IHTOA IHC Additional, Tech Only No No

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).

Method Name

Immunohistochemistry (IHC)

Reporting Name

CTSK IHC, Tech Only

Specimen Type


Specimen Stability Information

Specimen Type Temperature Time Special Container
TECHONLY Ambient (preferred)

Clinical Information

·        Cathepsin K is a protease whose expression is driven by microphthalmia transcription factor (MITF) in osteoclasts. Cathepsin K is also expressed in renal perivascular epithelioid cell neoplasms (PEComas), alveolar soft part sarcoma, and most MiT family translocation -renal cell carcinomas. This includes most transcription factor EB- (TFEB) rearranged renal cell carcinomas, those with amplifications of TFEB, and renal cell carcinomas that harbor various TFE3 gene fusions.


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 and documentation is retained at Mayo Clinic Rochester. If a control tissue is not included on the slide, a scanned image of the relevant quality control tissue is available upon request. Contact 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.

Clinical Reference

1. Martignoni G, Bonetti F, Chilosi M, et al: Cathepsin K expression in the spectrum of perivascular epithelioid cell (PEC) lesions of the kidney. Mod Pathol. 2012;25(1):100-111. doi: 10.1038/modpathol.2011.136

2. Rao Q, Cheng L, Xia QY, et al: Cathepsin K expression in a wide spectrum of pervascular epithelioid cell neoplasms (PEComas): a clinicopathological study emphasizing external PEComas. Histol. 2013;62(4):642-650. doi: 10.1111/his.12059

3. Martignoni G, Gobbo S, Camparo P, et al: Differential expression of cathepsin K in neoplasms harboring TFE3 gene fusions. Mod Pathol. 2011;24(10):1313-1319. doi: 10.1038/modpathol.2011.93

4. Rao Q, Wang Y, Xia Q, et al: Cathepsin K in the immunohistochemical diagnosis of melanocytic lesions. Int J Clin Exp Pathol. 2014;7(3):1132-1139

Day(s) Performed

Monday through Friday

Report Available

1 to 3 days

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
CTSK CTSK IHC, Tech Only Order only;no result


Result ID Test Result Name Result LOINC Value
607888 CTSK IHC, Tech Only Bill only; no result


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

Mayo Clinic Laboratories | IHC Catalog Additional Information: