Pathology/Lab Coding Alert

Question: Our lab is performing a method new to us, which uses a dual-color in situ hybridization stain on paraffin embedded slides to identify Kappa/Lambda in assessing B cell clonality. The pathologist reviews the slides and identifies the tissue as Kappa/Lambda positive or negative, rather than reporting a quantitative measure. How should we report this?

California Subscriber

Answer: The correct coding for the procedure you describe is 88366 (In situ hybridization [e.g., FISH), per specimen; each multiplex probe stain procedure).

This is a qualitative ISH stain, because the pathologist is not enumerating the findings, so you should use the 88365 code family rather than a code for morphometric ISH analysis.

CISH included: Although the code definition gives the example of FISH (fluorescence ISH), it’s just an example. The procedure you describe is chromogenic ISH, which reports to the same code.

Multiplex: You’ve described a stain procedure that has two ISH probes. This is a single procedure in which the pathologist simultaneously evaluates the various color signals while observing the slide through the microscope and reaches a single evaluation of clinical significance. That means you should not code this as two separate ISH stain procedures using the following codes:

• 88365 — In situ hybridization (e.g., FISH), per specimen; initial single probe stain procedure 
• +88364 — …each additional single probe stain procedure (List separately in addition to code for primary procedure).