A Guide To Biopsy Techniques

When is it appropriate to use punch or shave biopsies for dermatologic conditions? This author takes a closer look at the utility of these biopsy methods and more, offering pearls on technique, preparation and biopsying pigmented lesions.

In your practice, how often do you biopsy skin or nail lesions? Which skin biopsy technique(s) do you typically use: punch, shave or incisional/excisional? When you visit a dermatologist for your own yearly skin check, what type of biopsy have you received on your skin?

With much certainty, I can say you probably have performed biopsies for your patients and have had shave biopsies done on your own skin. Have you considered a variation on the shave biopsy technique? You might think, what is the difference and why should I consider doing a punch biopsy versus a shave biopsy? Accordingly, let us take a closer look at the similarities and differences between these procedures.  

First, one has to consider the reason for performing a skin biopsy. The histopathologic results of a biopsy may confirm or deny the differential diagnoses the practitioner had in mind. Often, I use a skin biopsy in my own practice to determine if I am dealing with an unusual skin condition when it has not responded to the typical therapies for the symptoms presented. This ultimately assists me in directing treatment and supports my diagnosis to the insurance company if necessary for prior authorization purposes.

In many cases, a skin biopsy can save a life by establishing a diagnosis of either a non-melanoma skin cancer (basal cell or squamous cell) or a melanoma. When a patient has a recently changed wound or a wound that has been present for 20 years, a skin biopsy can assist the practitioner to rule out the ulcer’s transformation into a squamous cell carcinoma.

With so many reasons to utilize a biopsy in practice, why do practitioners shy away from it in their practice? Cost of the equipment, time spent doing the procedure and fear of “what comes next?” after the results return are some of the anecdotal reasons podiatric practitioners have cited for not performing these procedures in the office. The reality is, if one misses a skin cancer diagnosis or diagnoses every rash as a fungal infection and treats that rash with the inappropriate medications, the time spent dealing with the repercussions of these situations will be greater than the time it takes to perform a skin biopsy in the first place.  

The various types of skin biopsies (shave, punch, excisional/incisional, electrodessication and curettage) play roles in providing that histopathologic diagnosis for the practitioner. That said, there are advantages and disadvantages to using each technique. For this article, we will focus specifically on the shave and punch skin biopsy techniques.  

Essential Tips For Biopsy Preparation

The equipment needed for both the punch and shave biopsies is simple, and the staff can prepare it each morning so there is no delay when a potential patient is in the treatment room.

It is useful to have labeled and preloaded 1 cc syringes of lidocaine 1% or 2% (with or without epinephrine) with a 27 gauge or 30 gauge half-inch needle available. For a shave biopsy, a #15 blade and a topical hemostatic agent are the other tools the clinician will need. For a punch biopsy, a range of 3 or 4 mm (6 mm for larger areas) skin punch tools along with suturing material and its associated instruments (if you choose to suture) are required. Proper fixative medium for the pathology lab appropriate for the patient’s insurance should be in the treatment room prior to the clinician obtaining the specimen.     

After having obtained consent and prepped the site, one can perform an infiltrative intradermal injection of local anesthetic. Using a 30-gauge, half-inch needle (with the bevel facing up), I prefer to inject 1 cc of lidocaine with epinephrine. There is a blanching effect of the area and minimal pain. Ultimately, however, the intradermal technique offers immediate anesthesia by raising a small wheal, which enables one to perform the biopsy without delay.  

Key Insights On Performing A Punch Biopsy

The punch biopsy can offer a useful and simple way of supporting a clinical diagnosis. Punch biopsy is generally the best biopsy technique for diagnosing dermatitis since it delivers a full-thickness cylindrical specimen. Podiatrists should reserve the punch biopsy for neoplasms, vesicles and inflammatory skin disorders. A punch biopsy can be incisional (it removes a part of the lesion) or excisional (removing a small nevi in toto, for example).

One can perform this biopsy in minutes with little discomfort to the patient. Prior to infiltration, gently pinch the skin in order to find the relaxed skin tension lines.¹ These lines can subsequently serve as a guide to suture the biopsy site to minimize scarring.  

After obtaining anesthesia for the patient, apply a disposable punch (3, 4 or 6 mm depending on the size of the lesion) to the skin. Use the dominant hand to hold the punch instrument while using the other hand to place a gentle perpendicular force to the relaxed skin tension lines away from the lesion. This enables you to avoid “dog ears” when closing the defect.  

When it comes to the dorsum of the foot, be careful about controlling the depth of the biopsy to avoid important structures deep to the lesion. On the plantar foot, use the entire cutting depth of the punch. After performing the punch, gently lift the circular button of skin and subcutaneous tissue. Using an iris scissor, cut the fatty attachment as deeply as possible in order to give all three levels of skin to pathology. Do this gently so as not to crush the specimen. Proceed to suture the defect. Have the patient return in 10 to 14 days for both suture removal and diagnosis review.  

For most skin lesions, one can send the specimen in formalin. However, if you have performed a punch biopsy of a vesicle (perilesional biopsies especially) or vasculitic lesion, you should consult the lab for the best medium for transport. Those lesions are usually subject to immunofluorescence studies of certain proteins that can be affected negatively when one places the specimen in formalin. By preparing for this medium difference, the physician can spare the patient another biopsy.  

Many practitioners do not utilize the punch biopsy as frequently as the shave biopsy as it takes more time and has more overhead cost (if one sutures the defect). Also, the patient may feel inconvenienced to return in a specified time for suture removal.

As a podiatric practitioner, I utilize the punch biopsy the most out of all the techniques. I prefer to give a consistent full thickness specimen (epidermis, dermis and some subcutaneous tissue) to the pathologist to achieve the best histopathologic diagnosis for the wounds, inflammatory skin conditions, and blistering diseases I treat. As a personal preference, I suture all of my punch biopsies as I am concerned about wound healing and infection once the patient bears full weight and places the foot in shoe gear.

Studies have shown that post-punch biopsy healing by secondary intention versus suturing for 1 to 4 mm lesions have similar cosmetic outcomes.² However, these studies did not take into account a weightbearing surface or an enclosed anatomic area such as the foot. In that study, patients who had punch biopsies larger than the 4 mm tool preferred the visual appearance of a primarily closed defect.  

Relevant Pearls For Obtaining A Shave Biopsy

Due to the quickness of the technique and low cost, shave biopsies are the most commonly performed technique by dermatologists and non-dermatologists alike.⁴ The shave biopsy is the best technique for exophytic lesions such as a filiform wart (not an endophytic plantar wart), skin tag and seborrheic keratoses. A simple, superficial shave is not recommended for a suspicious pigmented lesion due to its inability to give a full-thickness specimen.⁵  

As with the punch biopsy, once local anesthetic infiltration has occurred, using a #15 blade or an autoclaved double- edged razor, the practitioner places the device parallel to the skin and generates a thin piece of tissue that encompasses the epidermis and an aspect of the dermis. This technique will help the area heal by secondary intention and does not require sutures. Send the thin, flat specimen to the pathology lab in a formalin-filled container. One can achieve topical hemostasis with a hyfrecator or by applying topical aluminum chloride 20% solution. Apply an appropriate dressing and review patient home care. The patient may return in 10 to 14 days for review of the pathology report and incision site check.  

One of the drawbacks of the simple shave biopsy is it generates a specimen of varying depth that is not truly full thickness. A variation on the shave technique is the saucerization biopsy.³ By curving the double-edged razor or using the #15 blade to take a deeper, thicker specimen under the plane of the suspected lesion, one can generate a deeper shave specimen that encompasses the epidermis, most of the dermis and possibly some subcutaneous tissue. Swanson and coworkers noted the saucerized shave biopsy leaves a more appealing scar than an elliptical excision.^{6 The} saucerization technique is what I prefer when there are pigmented streaks or longitudinal melanonychia on the nail unit. I appreciate the ability of the saucerized shave biopsy to produce a thicker specimen that has a smaller chance than a punch biopsy in the nail unit at causing long-term nail dystrophy in the nail matrix.  

What You Should Know About Biopsies For Pigmented Lesions

When examining a possible melanoma or other pigmented lesion, there is controversy among practitioners as to which biopsy type to choose. Even among dermatologists, there is variation in clinical practice when facing a suspicious pigmented lesion.

Farberg and Rigel polled the biopsy preferences of United States dermatologists when dealing with cutaneous malignant melanoma.⁷ They found the most common utilized techniques for initial evaluation of a pigmented lesion were shave (35 percent), small excisional biopsy (31 percent), saucerization (12 percent), punch (11 percent) and wide excision (3 percent).

Farberg and Rigel also compared these results to the current recommendations set forth by the American Academy of Dermatology and the National Comprehensive Cancer Network.⁷ These institutions show a preference of a narrow excisional biopsy with a margin of 1 to 3 mm as the initial management of a suspicious pigmented lesion. This “narrow excisional” biopsy is defined as a punch with sutures, elliptical excision or saucerization (performed to have a depth below the plane of the lesion and when the suspicion of melanoma is low) in which one removes the entire lesion, leaving clinically negative margins. Follow-up surgical excision for a diagnosed melanoma involves planning a margin ranging from 0.5 to 2 cm, depending on the depth of the lesion.

Ultimately, the initial biopsy should have a specimen depth conducive for staging of the melanoma. A simple shave biopsy is inadequate to do this and would impede a diagnosis of malignant melanoma whereas an elliptical excision or punch biopsy would better achieve the depth the pathologists require for this calculation. Keep in mind that a lackluster specimen that doesn’t encompass the depth needed may lead to a misdiagnosis (i.e., a lesser-staged melanoma or another diagnosis entirely), which can have challenging consequences for both you and the patient.  

In Conclusion

For an initial biopsy of a skin or nail lesion, there are several techniques from which to choose (see the table “A Guide To Indications For Biopsy Types” above at right). For wounds, blistering rashes or inflammatory dermatoses, a punch biopsy will be the most helpful in diagnosing. With exophytic lesions like skin tags, seborrheic keratoses and other papular lesions, a simple shave will suffice.  

However, when it comes to a pigmented streak in the nail unit, utilize a deeper saucerization shave or punch biopsy. For pigmented lesions in which the suspicion of melanoma is low, one may use a saucerization shave biopsy. However, for any suspicious lesion, a biopsy technique that will give adequate depth for melanoma staging is key. In certain situations, a punch biopsy or elliptical excision will be the best techniques for achieving the depth required for staging of a malignant melanoma.

Ultimately, with either technique, it is about providing a specimen that will give the pathologist the most information in order to assist in diagnosis and the patient achieving peace of mind. 

Dr. Vlahovic is a Clinical Associate Professor in the Department of Podiatric Medicine at the Temple University School of Podiatric Medicine.

References

1.     Olbricht S. Biopsy techniques and basic excisions. In: Bolognia JL, Rapini RP, et al. (eds): Dermatology, First Edition, Mosby, London, 2003, pp. 2269-2286.
2.     Christenson LJ, Phillips PK, Weaver AL, Otley CC. Primary closure vs second-intention treatment of skin punch biopsy sites: a randomized trial. Arch Dermatol. 2005;141(9):1093–1099
3.     Pickett H. Shave and punch biopsy for skin lesions. Am Fam Physician. 2011;84(9):995-1002.
4.     Tran KT, Wright NA, Cockerell CJ. Biopsy of the pigmented lesion—when and how. J Am Acad Dermatol. 2008;59(5):852–871.
5.     Tadiparthi S, Panchani S, Iqbal A. Biopsy for malignant melanoma—are we following the guidelines? Ann R Coll Surg Engl. 2008;90(4):322–325.
6.     Swanson NA, Lee KK, Gorman A, Lee HN. Biopsy techniques. Diagnosis of melanoma. Dermatol Clin. 2002;20(4):677–680.
7.     Farberg AS, Rigel DS. A comparison of current practice patterns of US dermatologists versus published guidelines for the biopsy, initial management, and follow up of patients with primary cutaneous melanoma. J Am Acad Dermatol. 2016;75(6):1193-7.

For further reading, see “When Should You Biopsy?” in the June 2013 issue of Podiatry Today, “A Guide To Biopsy Techniques For Skin Neoplasms” in the May 2009 issue or the June 2009 DPM Blog “Should We Biopsy Everything?” by William Fishco, DPM, at https://tinyurl.com/kjmlltr .