Pathology/Lab Coding Alert

Question: When we process a sentinel lymph node biopsy, we typically prepare four or five paraffin blocks. Each block is serially sectioned, and we use an S100 stain on three sections from each block. Is it appropriate to report each stain individually, or should we report the stain once for each block?

Colorado Subscriber

Answer: The evaluation of the sentinel lymph node biopsy is reported with 88307 (Level V Surgical pathology, gross and microscopic examination, sentinel lymph node). Special staining involved in the evaluation of a sentinel lymph node biopsy is separately reportable.

The S100 is a histochemical stain, which is reported using 88342 (Immunocytochemistry [including tissue immunoperoxidase], each antibody). The unit of service for this stain is the specimen, which in this case is the sentinel lymph node. Regardless of how many paraffin blocks are made from the specimen, or how many slides are stained from each block, only one unit of 88342 may be reported for the S100 staining of a single sentinel lymph node. If a separate histochemical stain were used, that stain would be separately reportable because the 88342 code definition states, "each antibody."