A Guide To Biopsy Techniques For Skin Neoplasms

General guidelines for obtaining biopsies of skin lesions are few and far between. These techniques are also often underutilized in podiatric practice. Accordingly, this author offers a helpful primer on when and how to perform punch, incisional and excisional biopsies.

   Why does a physician perform a skin biopsy? Often skin neoplasms and inflammatory conditions look alike and are clinically confusing. In these cases, a biopsy can facilitate a histopathologic diagnosis, which helps to support the treatment plan.1

   Obtaining a skin biopsy can also help to clarify the skin disorder when a treatment plan is not yielding the appropriate results. For example, perhaps a topical antifungal is not yielding effective results in treating the inflammatory disorder.

   Lastly, a biopsy can be curative or even lifesaving if one excises the lesion in toto or when the biopsy helps identify a treatable malignant diagnosis. Ultimately, a biopsy can both complement and confirm the diagnosis.2

   In order to have the best biopsy result, physicians must ensure all three layers of skin (epidermis, dermis and subcutaneous tissue) are present.

   A “scraping” of the skin, in which one sends the scales of the lesion to pathology, is not appropriate to diagnose any inflammatory skin disorder or neoplasm. Physicians should only use this “scraping” technique when doing a potassium hydroxide (KOH) test to determine the presence of a dermatophyte.

   Podiatrists should also avoid superficial shave biopsies as they do not involve the deep dermis or subcutaneous tissue, which is needed for many histopathologic diagnoses and staging of the neoplastic disease.

   Both the “scrape” and superficial shave ultimately delay a true diagnosis and create a lot of frustration for the patient. Additionally, physicians should never perform the scrape and superficial shave if they suspect a malignant lesion.

   When it comes to biopsies in the podiatric physician’s office, one should be familiar with the punch biopsy, the incisional biopsy and the excisional biopsy.

   In addition to performing the appropriate procedure, giving the pathologist sufficient clinical information is important in order to receive a helpful diagnosis.3 When you are filling out the pathology form, provide sufficient detail on the evolution of the lesion or dermatitis, the clinical description, the specific anatomic location of the biopsy site, and the differential diagnosis.

   What should the podiatric physician biopsy? Ideally, you should biopsy any inflammatory lower extremity disorder with a questionable diagnosis, any blistering “rash” and any suspicious neoplasm.2

   Podiatrists should always obtain consent and forewarn the patient about the possible need for further surgery. For example, a second excision may be necessary for an atypical or malignant lesion. One should also counsel the patient about the possibility of a painful scar, especially when the lesion in question involves the plantar foot.

   To reiterate, the location of biopsy and use of the proper fixative medium are also imperative for optimum results.

   What should one avoid? When it comes to sites of active infection, physicians should not biopsy these unless they need more information about them (i.e. cutaneous larva migrans). One should also refrain from biopsies for areas that are excoriated or crusted, or when there are older stages of dermatitis as a biopsy in these clinical scenarios will give a vague diagnosis.

Essential Insights On The Punch Biopsy

   The punch biopsy can offer a useful and simple way of supporting a clinical diagnosis. One can perform this biopsy in minutes with little discomfort to the patient. Podiatrists should reserve the punch biopsy for neoplasms, vesicles and inflammatory skin disorders.

   After obtaining consent and prepping the site, one can perform a local infiltrative intradermal injection of local anesthetic. Using a 30-gauge, ½ 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.

   Prior to infiltration, you can gently pinch the skin in order to find the relaxed skin tension lines.1 One can subsequently use these lines as a guide to direct the biopsy in order to give the best scar.

   After obtaining anesthesia for the patient, apply a 4 or 6 mm disposable punch 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 edge of the punch. Once you have performed 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.

   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 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 if one places the specimen in formalin. By preparing for this medium difference, the physician can spare the patient another biopsy.

   Punch biopsy is generally the best biopsy technique for diagnosing dermatitis. However, one can use it for multiple skin disorders and neoplasms. In regard to optimum time, location and possible indications for the use of the punch biopsy, see “A Salient Overview To Performing The Punch Biopsy” on page 54.

Pertinent Points On Incisional And Excisional Biopsies

   When one can completely excise a lesion with a margin of unaffected skin, an excisional biopsy is warranted. In circumstances in which just a part of the lesion is required, an incisional elliptical biopsy is warranted.

   With both incisional and excisional biopsies, one often draws an ellipse with the 3:1 parameters (with the length being three times the width) and a 2 mm border around the lesion.

   As with the punch biopsy, it is important to consider relaxed skin tension lines in order to facilitate the best scar outcome and complete the biopsy down to subcutaneous tissue. Once you have obtained consent and prepared the surgical site, use the aforementioned intradermal anesthesia technique. If the lesion is larger than 4 mm, one can also use a diamond block to create anesthesia around the area of the ellipse.

   The elliptical incision should be parallel to the relaxed skin tension lines for the best scar. After the first pass of the 15 blade, deepen the incision to include the subcutaneous tissue. Proceed to dissect the ellipse of skin carefully in one plane and send the specimen in formalin (or another media if a vesicle). One may employ simple interrupted or running sutures to close the defect.

   The technique for incisional biopsy is the same as the excisional biopsy. The only exception is the incisional biopsy does not remove the lesion completely.

   If a lesion is too large to remove completely in the office, the thickest portion of the lesion with a margin of normal skin is the ideal place for biopsy.

   The incisional biopsy is also best for ulcers. For example, if a podiatric physician suspects a venous stasis ulcer has elements of squamous cell carcinoma, an incisional biopsy of the fungating granulation tissue with a margin of the peri-wound skin is an ideal place to start when it comes to confirming the diagnosis.4,5

   In regard to possible indications for incisional and excisional biopsies, see “When Should You Consider Incisional And Excisional Biopsies?” on page 56.

When You Should Opt For Curettage And Electrodesiccation

   When it comes to verruca or previously biopsied basal cell carcinomas that are superficial in nature, physicians may use curettage and electrodesiccation.

   One can prep the area without an alcohol wipe and use the aforementioned infiltration technique. With firm strokes, the physician should apply the curette over the lesion. Only send the first pass with the curette in formalin to pathology.

   Following curettage, apply topical hemostasis with a handheld electrocautery device. Perform curettage and electrodesiccation twice more to complete the procedure. Bear in mind that sending the curetted material after electrodesiccation will not aid in the diagnosis at all.

   Curettage provides a fragmented specimen to the pathologist and does not aid in diagnosing inflammatory skin disorders, neoplasms and other diseases.1 One should only use curettage for the two aforementioned indications above. Also be aware that the affected area will heal by secondary intention and leave a minimal scar.

When Nails Require A Biopsy

   The nail biopsy is underutilized in podiatric medicine. When it comes to biopsy of the nail, physicians generally use the punch biopsy or incisional/ excisional biopsies.

   When a patient presents with a dark brown to black longitudinal line (longitudinal melanonychia) in the nail, the physician must use his or her best judgment on whether to do a punch biopsy. These lines are present in every toenail and fingernail in 100 percent of African-American patients by the age of 50.6

   However, if the longitudinal melanonychia changes in these patients or if the patient is Caucasian, one should obtain a punch biopsy. The podiatric physician should not wait for the pigmentation to spill out onto either the distal or proximal digit. This pigmentation, or Hutchinson’s sign, signals extensive disease and usually yields a poor prognosis.

   Generally, longitudinal melanonychia presents for the entire length of the nail. When it comes to planning of a punch biopsy of that lesion, the physician should always involve the most proximal part of pigmented area due to the pigmentation originating from melanocytes in the matrix portion of the nail unit. Therefore, one should dissect the proximal nail fold back carefully to expose the nail matrix.

   Direct a 4 mm punch (or smaller/larger depending on the size of the lesion) to the most proximal part of the pigmented area. Using a gentle motion, excise a small circular area.7 Remember that there is no subcutaneous tissue deep to the nail unit. The punch instrument will most likely touch the distal phalanx. One can fill the circular defect with Gelfoam or another hemostatic agent, and close the proximal nail fold with appropriate suture technique.

   In regard to the small button of nail plate and nail bed, do not tease them apart and be sure to send the specimen in formalin for processing. Due to the disturbance of the matrix during this procedure, it is imperative to discuss with the patient during the informed consent process that permanent dystrophy may occur as the nail grows distal. However, if a neoplasm is uncovered, it is unlikely that the patient will be disturbed by this fact.

   If a patient presents with a nail bed neoplasm, one may obtain an incisional or excisional biopsy depending on the size of the lesion. Surgical planning involves first removing the nail plate in order to gain access to the nail bed.7

   In regard to excising a neoplasm from the nail bed, this is unlikely to cause permanent nail dystrophy due to the distance from the matrix. After excising the lesion, place it in formalin and send it for histopathologic processing. The physician may also send the nail plate if he or she feels it would aid in the diagnosis.

When The Pathology Results Return

   If podiatric physicians have any questions regarding the histopathologic diagnosis, they should not hesitate to speak with the pathologist for clarification. Proper and prompt communication will only benefit the patient.

   If the lesion is malignant with Clark’s level, Breslow’s depth and affected margins noted, the podiatric physician may choose to send the patient to an oncological surgeon, a Mohs surgeon or a plastic surgeon for further care.

   If the lesion returns as in situ (superficial epidermis), the physician may choose to re-excise the lesion using the excisional biopsy method in order to have a pathology report return with “margins clear” of neoplasm. One should also refer the patient to a dermatologist for a full body skin check to determine if there are any similar lesions to those on the lower extremity.

Final Notes

   Skin biopsies are simple procedures to do but they can yield a great result. More often than not, a biopsy will prevent a delayed or incorrect diagnosis. Overall, the punch, incisional and excisional biopsies should become part of the podiatric armamentarium, and not be underutilized any longer.

Dr. Vlahovic is an Associate Professor at the Temple University School of Podiatric Medicine in Philadelphia. She is a Fellow of the American Professional Wound Care Association (APWCA).

For further reading, see “How To Differentiate Soft Tissue Neoplasms” in the January 2008 issue, “Expert Insights On Diagnosing Pigmented Skin Lesions” in the April 2005 issue, “Soft Tissue Masses: When To Treat, When To Refer” in the May 2006 issue and “Identifying Skin Malignancies On The Distal Lower Extremity” in the September 2003 issue.

To check out the archives or get information on reprints, visit www.podiatrytoday.com.

References:

1. Olbricht S. Biopsy techniques and basic excisions. In: Bolognia JL, Rapini RP, et al. (eds) Dermatology (1st Edition) Mosby, London, pp 2269-2286, 2003. 2. Sina B, Kao G, Deng A, Gaspari A. Skin biopsy for inflammatory and common neoplastic skin diseases: optimum time, best location, and preferred techniques. A critical review. J Cutan Pathol 2009; 36(5):505-10. 3. Mehregan D, Dooley V. How to get the most out of your skin biopsies. Int J Dermatol 2007; 46(7):727-33. 4. Jankovic A, Binic I, Ljubenovic M. Basal cell carcinoma is not granulation tissue in the venous leg ulcer. Int J Low Extrem Wounds 2008; 7(3):182-4. 5. Spear M. Pyoderma gangrenosum: an overview. Plastic Surg Nurs 2008; 28(3):154-7. 6. Dawber RP, Baran R, Berker D. Science of the nail apparatus. In: Baran R, Dawber RP, eds. Diseases of the Nails and their Management (2nd edition). Blackwell Scientific Publications, Oxford, England; pp 1-34, 1994. 7. Rich P. Nail Surgery. In: Bolognia JL, Rapini RP, et al. (eds) Dermatology (1st Edition) Mosby, London, pp 2321-2230, 2003.