I don't feel you necessarily have to use different Dx codes per CPT in this case. If the biopsy or excision was planned, then yes, the office visit could only be billed if it was "significant, separately identifiable," from the other procedure (related to different diagnoses).
However, lets look at a new patient visit. The patient comes in, full workup is done, and the decision is made to remove a suspisious lesion on the thigh. Since modifier 57 is only appropriate for 90-day global surgies, we would use a modifier 25. The full workup is more than enough to support the office visit charge. The visit was not only focused on this one lesion or one body area.
~Melanie, CPC~