Clinical Review
4. CHOOSE AN EXCISIONAL BIOPSY FOR A MELANOCYTIC NEOPLASM, WHEN POSSIBLE
The purpose of an excisional biopsy (which typically includes a 1- to 3-mm rim of normal skin around the lesion) is to completely remove a lesion. Excisional biopsy generally is the preferred technique for clinically atypical melanocytic neoplasms (ie, lesions that are not definitively benign).4-8
When suspicion for melanoma is high, excisional biopsies should be performed with minimal undermining to preserve the accuracy of any future sentinel lymph node biopsy surgeries. Excisional biopsy is the most involved type of biopsy and has the largest potential for cosmetic disfigurement if not properly planned and performed. While guidelines from the American Academy of Dermatology state that “narrow excisional biopsy that encompasses [the] entire breadth of lesion with clinically negative margins to ensure that the lesion is not transected” is preferred, they also acknowledge that partial sampling (incisional biopsy) is acceptable in select clinical circumstances,9 such as when a lesion is large or on a cosmetically sensitive site (eg, the face).10
While a larger punch biopsy (6 or 8 mm) or even deep shave/saucerization may function as an excisional biopsy for very small lesions, this approach can be problematic. For one thing, these techniques are more likely than an excisional biopsy to leave a portion of the lesion in situ. Another concern is that a shave biopsy of a melanocytic lesion can lead to error or difficulty in obtaining the correct diagnosis on later biopsy.11 For pathologists, small or incomplete samples make it challenging to establish an accurate diagnosis.12 Among melanomas seen at a tertiary referral center, histopathologic misdiagnosis was more common with a punch or shave biopsy than with an excisional biopsy.9
It has been shown that partial biopsy for melanoma results in more residual disease at wide local excision and makes it more challenging to properly stage the lesion.13,14 If a shave biopsy is used to sample a suspected melanocytic neoplasm, it is imperative to document the specific site of the biopsy, indicate the size of the melanocytic lesion on the pathology requisition form, and ensure that all (or nearly all) of the clinically evident lesion is sampled. Detailing the location of the lesion in the chart is not only essential in evaluating the present lesion, but it will serve you well in the future. Without knowing the patient’s clinical history, benign nevi that recur after a prior biopsy can be difficult to histologically distinguish from melanoma (see Figure 3). For more on this, see tip #7.
5. BE CAREFUL WITH CURETTAGE
Curettage is a biopsy technique in which a curette—a surgical tool with a scoop, ring, or loop at the tip—is used in a scraping motion to retrieve tissue from the patient. This type of biopsy often produces a fragmented tissue sample. Its continued use reflects the speed and simplicity with which it can be done. However, curettage destroys the architecture of the tissue of the lesion, which can make it difficult to establish a proper diagnosis, and therefore it is best avoided when performing a biopsy of a melanocytic lesion (see Figure 4).
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