Biopsy Techniques and Basic Excisions

Site Selection

Performance of a biopsy that will yield accurate and relevant histologic information depends upon the selection of an appropriate lesion or site within a lesion ( Table 146.1 ).

The anticipated depth of the lesion to be biopsied must also be considered. In the case of a superficial lesion, e.g. an actinic keratosis versus Bowen disease, it can be assessed via a more “superficial” biopsy that extends to the papillary dermis. On the other hand, accurate diagnosis of a subcutaneous nodule, e.g. panniculitis versus polyarteritis nodosa, requires a biopsy that includes subcutaneous tissue. Occasionally, fascia must be obtained, e.g. morphea profunda versus eosinophilic fasciitis. Disorders that primarily affect the collagen and elastic fibers within the dermis may have subtle histologic findings (e.g. atrophoderma of Pasini and Pierini) and longitudinally sectioned wedge biopsies that include both the affected area as well as adjacent normal-appearing skin prove most helpful.

Biopsy Technique Selection

Seven major methods are employed to biopsy skin: curettage, snip or scissors biopsy, shave biopsy, saucerization biopsy, punch biopsy, incisional biopsy, and excision in toto ( Table 146.2 ). Depending upon the type of lesion and its size, several of these procedures are also curative, especially excision in toto. However, these methods do differ with regard to the quality and quantity of skin obtained. Lesional characteristics and operator experience are factors that influence the choice of a particular procedure.

Curettage is frequently used to remove clinically benign epidermal lesions such as verrucae or seborrheic keratoses, actinic keratoses (AKs), and basal cell carcinomas (BCCs), especially the superficial type. The curettings can also be used to confirm the clinical diagnosis, but histologic interpretation may prove more challenging if the tissue specimen is fragmented and its orientation becomes problematic. Snip or scissors biopsy is an efficient technique for assessing pedunculated lesions as well as removing benign growths (e.g. acrochordons, filiform warts).

The shave biopsy usually provides a specimen consisting of epidermis, papillary dermis, and sometimes reticular dermis (particularly in elevated lesions). It is a popular biopsy technique for recontouring papular, clinically benign lesions (e.g. irritated or unwanted compound and dermal melanocytic nevi, fibrous papules of the nose) where histo­logic confirmation is desired. Shave biopsy is also a useful procedure for diagnosing superficial carcinomas, e.g. nodular and superficial BCCs, squamous cell carcinoma (SCC) in situ , and lentigo maligna.

Some authors distinguish a shave biopsy from a saucerization procedure in which the depth of the biopsy specimen is intentionally deeper due to angulation of the blade. This latter technique is often used to biopsy melanocytic nevi with atypical features when the differential diagnosis includes a thin melanoma . Its advantage is that it allows histologic examination of the entire lesion, which increases diagnostic accuracy, especially in the case of larger lesions (as compared to partial punch biopsy). Saucerization is also performed to confirm the clinical diagnosis of minimally invasive SCC or keratoacanthoma and to distinguish the former from a hypertrophic AK.

The punch biopsy supplies a cylindrical to conically shaped specimen consisting of epidermis, dermis and, sometimes, subcutaneous fat. The volume of tissue sampled correlates with the size of the punch biopsy instrument. In general, the diameter of the metal “barrel” varies from 2 to 6 mm, and the wider the diameter, the greater the likelihood of obtaining subcutaneous fat. However, the thickness of the dermis and the amount of subcutaneous fat required to establish the diagnosis must be kept in mind. Punch biopsies are particularly helpful for examining processes within the dermis, e.g. tumors, inflammation (see Table 146.2 ). In the case of tumors, sampling a majority of the lesion is desirable, so that for large-sized tumors, multiple punch biopsies may be required.

The incisional biopsy removes a wedge of tissue from the center or edge of a lesion (see Site selection ) and is the best option for obtaining deep subcutaneous fat or fascia for histologic examination. It is also used to sample a significant portion of large-sized tumors. Excision in toto removes the entire lesion and includes epidermis, dermis and subcutaneous fat. For these reasons, it is often utilized when the leading clinical diagnosis is invasive cutaneous melanoma.

Specimen Handling

Transportation of the biopsy specimen to the laboratory differs according to the processing and type of examination required. Most specimens are placed in formalin, but, occasionally, special carrier media are necessary ( Table 146.3 ). Fresh tissue specimens are sent on saline-moistened gauze and either promptly delivered to the laboratory or packed in ice; the laboratory must be in reasonable proximity and have the capability of processing the tissue immediately. When handling small or thin biopsy specimens, it is important to confirm that they are clearly within the formalin solution and not adhering to the upper portions of the container or lid; this prevents desiccation artifact.

A protocol must be established within the clinician's practice to ensure that specimens and results are appropriately tracked and assigned to the correct patient. Immediately after the biopsy specimen has been obtained, it should be placed in a container prelabeled with the patient's name and other identifying information. If multiple biopsies are to be performed, pre-labeling the containers alphabetically and with the respective sites avoids confusion. A specimen log book ( Table 146.4 ) ensures notification of the results to the patient and disposition of recommended care.

Patient Preparation

A discussion of the reason(s) to do the biopsy, the site to be biopsied, and the technique to be used can be brief and to the point. Informed consent requires a discussion of the major risks, which include bleeding, discomfort, infection, and scarring (see Ch. 151 ). Bleeding can usually be controlled by firm pressure at the site of the wound, but may require more aggressive forms of hemostasis. Discomfort is usually minimal, although some sites such as the forehead, fingers and feet may throb.

Infection is unusual. Except when the area to be biopsied is already infected or the site is mucosal, the skin can be prepared by application of an antiseptic agent and the procedure is then considered to be a clean procedure. For clean procedures of non-mucosal, non-infected sites, preoperative prophylactic antibiotics are currently not recommended, even in patients with artificial valves or joints (with the possible exception of sites at high risk of infection, e.g. groin, during the first 2 years after joint placement) . The overall goal is a reduction in the emergence of antibiotic-resistant bacteria and in one study, for example, preoperative prophylactic antibiotics increased nasal carriage of methicillin-resistant Staphylococcus aureus . Tables 151.2 and 151.3 review the guidelines for antibiotic prophylaxis as well as regimens for both oral and non-oral sites. Preoperative antibiotics are administered within a 2-hour window before the incision; there is debate as to whether or not a second dose is administered 6 hours later and under which circumstances antibiotics should be continued for 48–72 hours . When pretreated with a 5-day regimen of intranasal mupirocin ointment (twice daily) and a total body wash with chlorhexidine soap (daily avoiding the eyes and ears), nasal carriers of S . aureus were observed to have fewer postoperative infections .

Most patients are primarily interested in discussing whether or not there will be visible scarring. This is best predicted by the type of biopsy to be performed and the anatomic site. Generally, patients can be reassured that small biopsies may be done without grossly noticeable permanent “marks”.

Many patients are anxious about the needle sticks required for administration of the local anesthesia and the pain of the procedure. The patient's cooperation is easily obtained in an organized and peaceful environment with a calm and reassuring staff. A well-informed, comfortable patient in a supine position will tolerate the procedure without difficulty.

Site Preparation and Anesthesia

Effective site preparation is most efficient if a standard clinical protocol has been established ( Table 146.5 ). Marking and photographing the site , cleansing the skin ( Table 146.6 ) , and draping are important procedures prior to the instillation of local anesthesia. Local anesthesia is adequate for all skin biopsies and is reviewed in detail in Chapter 143 .

When the local anesthetic agent is instilled into a deep compartment (i.e. subcutaneous fat; Fig. 146.1A ), 5 to 10 minutes is required for anesthesia to develop on the surface of the skin. Gentle massage of the site may assist in spreading the agent subepidermally and achieving good anesthesia. Injection of the agent superficially, creating an edematous wheal, has immediate efficacy but is more painful ( Fig. 146.1B ). Since a punch or shave biopsy requires very little agent and therefore a very short injection time, superficial instillation is the technique often used. In addition, a wheal is helpful prior to a shave biopsy as the lesion is further elevated from the plane of the surrounding skin. Of note, since epinephrine (adrenaline) requires up to 15 minutes to produce maximal vasoconstriction and thereby minimize bleeding , lidocaine without epinephrine is sufficient for an immediate biopsy. Regardless of other considerations, it is critical to have the local anesthesia in the compartment that is to be biopsied, i.e. a superficial wheal may be entirely adequate as anesthesia for a shave biopsy but will not suffice for an incisional wedge biopsy that extends into the subcutaneous fat.