Background: 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.
Methods: 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.
Results: 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 <or=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.
Conclusions: 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.