Method of Biopsy and Incidence of Positive Margins in Primary Melanoma

Abstract

The staging of patients with primary melanoma is dependent on adequate sampling of the tumor thickness. Initial biopsies with a positive deep margin suggest inadequate sampling, potentially limiting accurate staging and affecting treatment decisions. To determine the efficacy of shave biopsy to adequately sample the tumor, we retrospectively reviewed our pathology database for original pathology reports of primary melanomas accessioned between 01/01/04 and 6/30/05. The biopsies were evaluated by technique, the presence of tumor at the margins of the specimen, and specimen thickness. We identified 240 cases of primary melanoma; 223/240 were analyzable. The specimens were divided by biopsy technique (excisional, n = 51; punch, n = 44; and shave, n = 128). Shave and punch specimens had a significantly higher percentage of positive margins than excisional specimens (50, 68, and 16%, respectively; P < 0.0001). Shave specimens had a significantly higher percentage of positive deep margins than punch or excisional specimens (22, 7, and 2%, respectively; P = 0.0009). For melanomas ≤1 mm, shave specimens had a significantly higher percentage of positive deep margins than punch or excisional specimens (17, 0, and 0%, respectively; P = 0.0014). There was a significant difference in specimen thickness (P = 0.0005), with shave specimens being the thinnest. The presence of tumor at the lateral margin of punch biopsies is an expected result, since this method is often used to diagnose lesions with a large diameter. The presence of positive deep margins in 22% of shave biopsy specimens compromises the ability of this technique to properly stage patients.