As you know, coverage by insurance companies varies greatly. A majority of dental insurance companies cover these fees. However, it would be prudent to verify with the company before submitting your sample.
General practitioners:
One only has to add the lab fees for the histopathological examination to the biopsy cost on the insurance form similar to lab fees for dentures or crowns (exemple).
Dental specialists:
One only has to add the lab fees for the histopathological examination under the code 04335 (histopathologic examination of a tissue biopsy).