Pathology/Lab Coding Alert

Question: The pathologist evaluated a breast biopsy specimen and used immunohistochemistry to determine the specimen is ER positive and PR negative. The pathologist also evaluated slides for the Ki67 marker and reported the findings as 36 percent Ki67 index. How should we report the case?

Montana Subscriber

Answer: You should report the pathology exam as 88305 (Level IV - Surgical pathology, gross and microscopic examination … Breast, biopsy, not requiring microscopic evaluation of surgical margins …). For the estrogen receptor (ER) and progesterone receptor (PR) stains, report 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)). You should also report 88360 (Morphometric analysis, tumor immunohistochemistry (eg, Her-2/neu, estrogen receptor/progesterone receptor), quantitative or semiquantitative, per specimen, each single antibody stain procedure; manual) for the Ki67 evaluation.

Although CPT^® lists multiple pathology exam levels for breast tissue, the report specifies that the tissue is a biopsy specimen, indicating that 88305 is the correct code. The higher pathology exam levels generally require more work, such as examining whether the surgical margins are clear.

Because the report simply identifies ER/PR status as positive or negative, not indicating a measure of the receptor level, you know that the pathologist’s evaluation is qualitative, not quantitative. That’s why you should use the immunohistochemistry (IHC) stain codes for the ER/PR evaluation

On the other hand, the report identifies Ki67 as a quantitative measure. Pathologists often use Ki67 as a marker for cellular proliferation, which may indicate the likelihood that the cancer is invasive. Because the report lists the findings as a 36 percent index, that means the procedure involved counting the number of Ki67 positive cells compared to the total number of cells to create the ratio. That procedure is quantitative, not qualitative. The report also indicates that the pathologist performed this evaluation, as opposed to an automated evaluation of the slide. For those reasons, the appropriate code for the work is 88360.