Pathology/Lab Coding Alert

Ensure that you’re up-to-date on IHC rules.

Your pathologist receives two sentinel lymph nodes for “lymphatic mapping” to help the oncologist with staging the patient’s malignant melanoma.

Read the following case to make sure you know how to capture all the pay your pathologist deserves for the sentinel lymph node evaluation.

Decode the Pathology Procedures

The pathologist receives two separate lymph nodes that the surgeon identifies by anatomic site based on radioactive tracer and isosulfan blue dye. The surgeon’s study indicates that these two nodes are the first to “drain” the site of the cutaneous melanoma.

Although the pathologist might perform a frozen section procedure for some sentinel lymph node biopsies, “that’s not common for most melanoma cases because of the higher risk of false-negatives for this type of cancer,” says R.M. Stainton Jr., MD, president of Doctors Anatomic Pathology Services in Jonesboro, Ark.

Instead, the pathologist opts for permanent section tissue preparation and evaluation for each distinct sentinel lymph node. The histotechnician processes the first sentinel node in four paraffin blocks labeled A1-A4, and the second sentinel node in five paraffin blocks labeled B1-B5, for a total of nine blocks.

Serial sections: For each block A1-A4 and B1-B5, the histotech cuts serial sections and removes five slides at three predetermined intervals for staining with Hematoxylin and Eosin (H&E). The pathologist examines these two specimens, evaluating 135 slides from the nine blocks for signs of metastasis.

First charge: Regardless of the number of blocks and slides, you should report 88307 (Level V - Surgical pathology, gross and microscopic examination … Sentinel lymph node …) for each sentinel node specimen — 88307x2 in this case. If you wrongly bundled the two distinct sentinel nodes into a single specimen, you’d stand to lose $312.21 (Medicare Physician Fee Schedule non-facility amount, conversion factor 35.8043) of legitimate pay for your pathology practice.

Watch for Special Stains

During the serial sectioning, the histotech also pulls four slides at the same three predetermined intervals for each block of each specimen and stains them with melanoma-associated tumor markers (108 slides). Specifically, the histotech stains half the slides with S100, which is very sensitive for melanoma micrometastases, and MART-1, which is highly specific for the same.

Understand IHC: S100 and MART-1 are both immunohistochemistry (IHC) markers that the pathologist looks for in the serial-sectioned slides to observe any micro-metastatic melanoma cells, if present. In this way, the pathologist can identify if the melanoma has begun to spread beyond the initial skin site. Pathologists perform this type of analysis because a significant portion of sentinel nodes may be negative for metastasis based on H&E slide examination, but demonstrate micrometastasis on closer examination with the tumor-specific melanoma markers.

Code this: For specimen A, you should report the S100 and MART-1 stained-slides as 88342 (Immunohistochemistry or immunocytochemistry, per specimen; initial single antibody stain procedure) and +88341 (…each additional single antibody stain procedure [List separately in addition to code for primary procedure]). Note that the unit of service is the “single antibody stain procedure” for a single specimen. Regardless of the number or blocks or slides, you should bill per specimen for each unique antibody stain. You should code specimen B the same way: 88342 and +88341.

Stay up-to-date: If you haven’t been paying attention recently, you might make an error in coding IHC stains. That’s because the CPT^® codes, CMS coverage rules, and even some temporary HCPCS Level II codes have been changing repeatedly the past couple of years. If you think you’re just sure you can code IHC stains per block, for instance, you might be remembering some past rules.

Old rules: You used to bill 88342 times the number of antibody stains, because you didn’t have an add-on code for the second and subsequent stains. Then in 2014, you were allowed to report IHC stains per block, not per specimen, and +88343 was an IHC code (now deleted). That is, you could bill per block unless you were billing Medicare in 2014, in which case you had to use some “G” codes, also now deleted. CPT^® 2015 changed the codes to the current configuration, and CMS payers now recognize those codes.

Bottom line: The correct codes for this case are 88307x2, 88342x2, and +88341x2.