Pathology/Lab Coding Alert

Question: We received a toenail matrix biopsy for melanoma, which the pathologist examined using S-100 staining on each of two blocks. How should we code the case?

Louisiana Subscriber

Answer: The correct code for the pathology exam of the nail matrix biopsy is 88305 (Level IV - Surgical pathology, gross and microscopic examination … Skin, other than cyst/tag/debridement/plastic repair …). You should additionally report the S-100 special stain as 88342 (Immunohistochemistry or immunocytochemistry, per specimen; initial single antibody stain procedure).

Toenail is an unlisted specimen, and pathologists typically assign it a work level of 88304 (Level III - Surgical pathology, gross and microscopic examination …) if they’re processing the nail for a condition such as fungus. In this case, however, the pathologist examines a biopsy that includes both skin and nail for melanoma, so the 88305 code is more appropriate.

Watch units: Even though you stated that the pathologist stained and examined two blocks from the specimen, you should report just one unit of 88342 for the S-100 immunohistochemistry stain. That’s because the unit of service for the code is “per specimen,” as clearly stated in the code descriptor.