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Immunohistochemistry (IHC)
Test Description

A well-defined subtype of colorectal cancer (CRC) is characterized by deficiencies in the mismatch repair (MMR) pathway. MMR status may impact prognosis and benefit of adjuvant chemotherapy. MLH1, MSH2, MSH6, and PMS2 protein expression (as assessed by IHC) and microsatellite instability analysis (MSI) assessed by PCR are well-established tools to screen for Lynch syndrome (LS), and such testing is recommended for all new colorectal cancer diagnoses. MMR IHC and molecular MSI testing also serve as companion diagnostic tests in a wide range of solid tumors for selection of certain immuno-oncology therapies.

Specimen Requirements
  • A formalin-fixed, paraffin-embedded (FFPE) tissue block is preferred specimen type
  • One (1) unbaked, unstained slide for H&E staining (required) and 4-8 (minimum 4) positively charged unstained slides (all cut at 4-5 microns) for panel, or 2-3 slides/stain for individual stains ordered
  • Block and slide identifiers should be clearly written and match exactly with the specimen ID and specimen labeling as noted on the requisition.
Storage and Transportation

Use cold pack for transport. Make sure cold pack is not in direct contact with specimen.

CPT Code(s)*
88342 x1, 88341 x 3 or 88360 x 4 or 88361 x 4
New York Approved
Level of Service
Stain Only
Turnaround Time

Global: 48 hours, Image Analysis (tech-only): 36 hours, Tech-Only (stain only): 24 hours

*The CPT codes provided with our test descriptions are based on AMA guidelines and are for informational purposes only. Correct CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed.