Tissue and Fluids: Sampling Techniques

Abstract

Full-thickness samples of skin are usually obtained surgically with a scalpel. Trephines or “punches” are often used for small samples of skin. They are made in different sizes (1–8 mm diameter). Distortion from rotational movement can be minimised by using a high speed punch which also allows critical back reference of constituents or activity to surface area (Black et al. 1970). If the tissue to be removed is localised and raised it may be removed by curettage and pendulous tissue may also be removed by diathermy. If small pieces of skin consisting mostly of epidermis with little upper dermis are required, e.g. for study of epidermal proliferation, these can be obtained by raising the skin with a hypodermic needle, clamping with fine forceps and slicing the tissue off with a scalpel. A variety of specially designed knives are available for obtaining broad sheets of skin consisting of epidermis and a thin layer of dermis. The electrokeratotomes all rely on the reciprocating action of a sharp surgical blade driven by an electric motor. With the Castroviejo electrokeratotome sample thickness can be set by adjusting the blade. Other instruments include the Davis and the Davol keratotomes. The latter has a disposable head, but the thickness of the specimen to be removed cannot be varied. Of the many manual devices the most useful for small samples (e.g. 2 cm²) is Silver’s knife which uses a safety razor blade, thickness of sample being set by adjusting the distance between the blade and the skin contact bar.