proper usage of 88342 Prosate Biopsy

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Our practice has our own "in house" pathology lab. We perform a prostate biopsy, we take multiple cores from the prostate. Then our in house pathologist performs (cpt: 88305) Level IV - Surgical pathology, gross and microscopic examination with multiple units.
Also, performs (cpt: 88342) Immunohistochemistry (including tissue immunoperoxidase), each antibody- we do multiple slides of different parts of the actual prostate.
Now, as of 2012- we were informed by Medicare that the cpt: 88342, we can only bill for one unit however we do multiple slides. What is the correct way for the billing/compliance for this specific code?