to the editor: As a family physician turned dermatologist, I always read with interest the articles in American Family Physician that deal with the diagnosis and management of skin diseases. I enjoyed reading “Punch Biopsy of the Skin,”1 for its discussion of punch biopsy indication and techniques. I found the article to be informative and well presented, with the exception of the described use of punch biopsy in the diagnosis of melanoma. The pitfalls related to the interpretation of a punch biopsy, with the limited length of skin available to examine, have been previously discussed in American Family Physician.2 Recent data show that, of the three basic techniques of suspected melanoma biopsy—excision, scoop shave, and punch—punch biopsy is the most likely to yield an uncertain result.3 This applies to determining the depth of melanoma, on which prognosis and definitive therapy is based, and correctly diagnosing the lesion. The only exception is the punch biopsy of a lesion that fits entirely within the punch.
“Doing the math” explains the difficulty. A suspicious lesion 1 cm in diameter has an area of 0.79 cm2. A “representative” 4-mm punch will sample 0.13 cm2, which is only 16 percent of the surface of the lesion. Three 2-mm punches, sometimes advocated for large facial lesions, sample less than 0.1 cm2 combined. Furthermore, the advice that one can sample the most suspicious part of the lesion is flawed because the most papular component of a melanoma may indeed represent the thickest part of the cancer or may, instead, be the benign melanocytic lesion out of which the melanoma arose. Since melanoma is diagnosed more by histologic appearance of what the melanocytes are doing than by what any individual melanocyte looks like, the most diagnostic portion of a lesion may be the darkest part, the lightest part, the amelanotic part, or the regressing part. Incorrectly determining the true depth and thickness of the melanoma may lead to inadequate therapy, but the real hazard is completely missing the diagnosis and allowing a life-threatening cancer to remain while the patient has been reassured that “everything is okay.”
Prognosis and definitive therapy are determined by tumor depth and thickness, and the best way to get this information remains a conservative excision of the entirety of the suspicious lesion. If the lesion is in a cosmetically sensitive area or is too large to do this, the largest incisional biopsy possible should be performed. The risk of incomplete information still exists with this technique, but at least much more tissue is available to examine than is obtained with a standard punch. Incomplete excision of a melanoma does not encourage metastatic spread or more aggressive biologic behavior. Thin lesions of limited size may be scoop-shaved by an experienced operator, but even this procedure is not recommended if a melanoma appears deeply invasive or ulcerated.
in reply: Dr. Meffert raises several important issues concerning the shortcomings of punch biopsy. When dealing with suspicious melanocytic lesions, excisional biopsy is generally preferable. For situations in which excisional biopsy cannot be performed, incisional biopsy is a good second choice.
The chapter1 and subsequent article2 on punch biopsy listed one of the indications for the procedure as establishing the diagnosis of melanoma. While punch biopsy is usually not the procedure of choice, it continues to be used by many physicians. Diagnosis of melanocytic lesions in certain sites (nailbed) may be best accomplished by punch technique in many primary care practices. Punch biopsy technique using larger (6-mm) trephines can actually achieve complete excision of a lesion. National guidelines3,4 have recognized the use of punch technique in diagnosing melanoma. Other specialties have also recognized punch biopsy as a method to diagnose cutaneous malignancy.5
Many family physicians receive instruction from their community subspecialists not to touch melanocytic lesions; they are warned that biopsy within a lesion (incisional or punch) could cause spread of a melanoma. Dr. Meffert correctly notes that biopsy does not promote the spread of a lesion.6 Family physicians were also warned not to touch lesions so that sentinel lymph node testing could be accomplished. We now know that sentinel lymph node procedures can be accurately performed as a secondary procedure. Family physicians should not be discouraged from participating in diagnosing melanoma.
The incidence of melanoma is increasing rapidly in the United States. Biopsy should be performed on suspicious lesions as soon as possible. If the family physician is not comfortable or skilled in biopsy of larger excisions, referral is appropriate; however, this may cause significant delay. Punch biopsy or multiple punch biopsies could possibly facilitate rapid diagnosis for some patients.
Punch biopsy for large melanocytic lesions does have pitfalls. False-negative results can occur using small area biopsies (2-mm or 3-mm punches). Trying to select the most significant area within a large lesion to biopsy can also lead to clinical inaccuracies. A referred patient recently had an acral lentiginous melanoma whose initial single punch biopsy was read as negative. While multiple biopsies could overcome some of the limitations associated with a single punch biopsy, multiple biopsies also have shortcomings. Further intervention or referral should be considered when a negative interpretation is provided for a punch biopsy specimen.
I urge physicians to perform an excisional or incisional biopsy whenever possible. However, I cannot agree with the conclusion that punch biopsies should never be performed on melanocytic lesions. In some practices, punch biopsy remains the only diagnostic option for a physician. Dr. Meffert correctly identifies the limitations of the punch technique and the problems with relying on a negative punch histologic interpretation; however, early biopsy is clearly what is needed, and family physicians must be involved if we are to reverse the increasing tide of melanoma deaths in the United States. We should not create additional barriers for family physicians that keep them from participating in this important public health problem.