Punch (Trephine) Biopsies
 An un-bisected punch or trephine biopsy. |
The punch or trephine biopsy is one of the most popular methods of sampling for diagnosis of inflammatory skin conditions. A special instrument is used to cut out a cylindrical shaped piece of skin. The skin core contains the full skin thickness with the main skin layers (epidermis, dermis, and subcutaneous) usually being present. The punch biopsy must be embedded so that sections are taken perpendicular to the epidermis. This typically means that the specimen will be laid on its side (it is rounded and has no clear edges), with the epidermis disc being clearly visible on one side. If the punch biopsy is larger than 0.4 cm in diameter, it may be bisected. In bisected punch biopsies, each half will be laid on its side (cut surface) into the block face.
