Applied Evidence

Biopsies for skin cancer detection: Dispelling the myths

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This review debunks 5 myths and provides the information you need to perform rapid, high-quality biopsies to detect skin cancers at their earliest stages.


 

From The Journal of Family Practice | 2018;67(5):270-274.

References

Skin disease accounts for up to 15% of primary care visits,1 with family physicians (FPs) frequently in the important position of determining if a growth requires a biopsy or referral.

Once it’s determined that a growth requires a biopsy, there is often uncertainty about which type of biopsy to perform. Insufficient knowledge of, and/or experience with, the various biopsy modalities may deter FPs from performing skin biopsies when they are indicated. To help fill the knowledge gaps and better position FPs to tackle skin cancer in its earliest stages, this article identifies and dispels 5 of the most common myths surrounding skin biopsies for the detection of basal and squamous cell carcinoma and melanoma.

MYTH #1

A punch biopsy is always preferred for suspected melanoma because it gets full depth.

A deep shave biopsy (saucerization)—not a punch biopsy—is usually the procedure of choice when biopsying a lesion suspected to be melanoma.2 The National Comprehensive Cancer Network (NCCN) "Melanoma Clinical Practice Guidelines in Oncology" state that an excisional biopsy (elliptical, punch, or saucerization) with a 1- to 3-mm margin is the preferred method of biopsy for suspected melanoma.3 However, a punch biopsy should be performed only if a 1- to 3-mm margin all around a suspected melanoma can be obtained. Otherwise, a saucerization or elliptical excision is preferred.3

The saucerization technique generally permits optimal sampling in terms of both the breadth and depth of the growth, providing the pathologist with sufficient tissue from both the epidermis and dermis (FIGURE 1).

Saucerization of a suspected melanoma image

Why are breadth/depth important? Breadth is important because showing the pathologist the epidermis (especially the edge) of a suspected melanocytic tumor allows for detection of pagetoid spread (upward movement through the epidermis) of melanocytes and of single melanocytes at the edge of a tumor. Single melanocytes at the edge of a tumor and pagetoid spread are histologic features of melanoma that help to distinguish these lesions from nevi, which tend to have nested melanocytes.2

Depth is important because it predicts prognosis and impacts management. For tumors 0.8 mm to 1 mm deep, a sentinel lymph node biopsy (SLNB) should be considered.3,4 Although the tumor depth threshold for a SLNB is still debated, most skin cancer experts in the United States agree that a melanoma thicker than 1 mm qualifies for this procedure. Some melanomas with high-risk features (such as ulceration) qualify for an SNLB even if they are <1 mm in depth.5 An SLNB provides prognostic information, and a positive SLNB directly affects staging.

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