Watch & Learn
Shave biopsy
Watch & Learn A how-to video series
PRACTICE RECOMMENDATIONS
› Use an excisional biopsy for a melanocytic neoplasm. C
› Choose a punch biopsy over a shave biopsy for rashes. B
› Properly photograph and document the location of all lesions before biopsy. A
› Provide the pathologist with a sufficient history, including the distribution and appearance of the lesion, and how long the patient has had it. A
Strength of recommendation (SOR)
A Good-quality patient-oriented evidence
B Inconsistent or limited-quality patient-oriented evidence
C Consensus, usual practice, opinion, disease-oriented evidence, case series
Most physicians do a satisfactory job in choosing when and how to do a skin biopsy, but there is always room for improvement. The 9 pointers we provide here are based on standard of care practices and literature when available, and also on our collective experiences as a pathologist/dermatologist (JM), dermatopathologist (DZ), primary care physician (BR), and dermatologist/Mohs surgeon (EB).
1. Choose your biopsy type wisely.
Using the appropriate type of biopsy can have the greatest effect on a proper diagnosis. The decision of which biopsy type to use is not always easy. The most common biopsy types are shave, punch, excisional, and curettage. Several reference articles detail each type of biopsy commonly used in primary care and how to perform them.1,2 (For a series of how-to videos that illustrate how to perform some of these biopsies, visit The Journal of Family Practice Multimedia Library at http://www.jfponline.com/multimedia/video.html.)
Each type of biopsy has inherent advantages and disadvantages. In general, the shave biopsy is most commonly used for lesions that are solitary, elevated, and give the impression that a sufficient amount of tissue can be sampled using this technique. The punch biopsy is the biopsy of choice for most “rashes” (inflammatory skin disorders).2 Excisional biopsy is used to remove melanocytic neoplasms or larger lesions. And curettage, while still used by some clinicians for melanocytic lesions because of its speed and simplicity, should almost never be used for diagnostic purposes. Each of these techniques is described in greater detail in the tips that follow.
2. When performing a shave biopsy, avoid obtaining a sample that's too superficial.
The advantage of the shave biopsy is that it is minimally invasive and quick to perform. If kept small while not compromising the amount of sample retrieved, the scars left by shave biopsies have the potential to blend well. The major disadvantage of the shave biopsy is that occasionally, if the shave is not deep enough, an insufficient amount of tissue is obtained, which can make it challenging to establish an accurate diagnosis.
Balancing the need to obtain adequate tissue while minimizing scarring takes skill and experience. Taking a biopsy that is inadequate is a common occurrence. At times, the physician’s clinical impression may be that a biopsy has obtained adequate tissue, but histologically only the superficial part of the skin surface has been sampled. This often is because of thickening of the superficial skin, whether as a manifestation of the anatomic site (eg, acral skin) or the disease process itself.
Unfortunately, this superficial skin often is nondiagnostic when unaccompanied by underlying epidermis and dermis. It is important to keep this in mind when obtaining a skin biopsy, especially when dealing with lesions that are very scaly or keratinized. An equivocal biopsy wastes time, energy, and money, and can negatively impact patient care.3 It can be difficult to balance practical aspects of the biopsy (ie, optimizing cosmetic outcomes, minimizing scarring and wound size) with the need to obtain sufficient tissue sampling (FIGURE 1).
3. Choose punch over shave biopsy for rashes.
In a punch biopsy, a disposable metal cylinder with a sharpened edge is used to “punch” out a piece of skin that can be examined under the microscope. Punch biopsy is the preferred technique for almost all inflammatory skin conditions (rashes) because the pathologist is able to examine both the superficial and deep portions of the dermis4 (FIGURE 2).
Pathologists use the pattern of inflammation, in conjunction with epidermal changes, to distinguish different types of inflammatory processes. For example, lichen planus is typically associated with superficial inflammation, while lupus is known to have prominent superficial and deep inflammation.
An inadequate punch biopsy sample can hinder histological assessment of inflammatory skin disorders that involve both the superficial and deep portions of the dermis and can make arriving at a definitive diagnosis more challenging. The diameter of a punch cylinder ranges from 1 to 8 mm. Smaller punch biopsies often create diagnostic challenges because they provide so little sample. A punch biopsy size of 4 mm is commonly used for rashes.
