Clinical Impact and Accuracy of Shave Biopsy for Initial Diagnosis of Cutaneous Melanoma

Abstract

Introduction: Effective treatment of malignant melanomas is dependent upon accurate histopathological staging of preoperative biopsy specimens. While narrow excision is the gold standard for melanoma diagnosis, superficial shave biopsies have become the preferred method by dermatologists but may transect the lesion and result in inaccurate Breslow thickness assessment. This is a retrospective cohort study evaluating an initial method of biopsy for diagnosis of cutaneous melanoma and indication for reoperation based on inaccurate initial T-staging.

Methods: We retrospectively analyzed consecutive patients referred to the Medical College of Wisconsin, a tertiary cancer center, with a diagnosis of primary cutaneous melanoma. Adult patients seen between 2015 and 2018 were included. Fisher's exact test was used to assess the association between method of initial biopsy and need for unplanned reoperation.

Results: Three hundred twenty three patients with cutaneous melanoma from the head and neck (H&N, n = 101, 31%), trunk (n = 90, 15%), upper extremity (n = 84, 26%), and lower extremity (n = 48, 28%) were analyzed. Median Breslow thickness was 0.54 mm (interquartile range = 0.65). Shave biopsy was the method of initial biopsy in 244 (76%), excision in 23 (7%), and punch biopsy in 56 (17%). Thirty nine (33%) shave biopsies had a positive deep margin, as did seven (23%) punch biopsies and 0 excisional biopsies. Residual melanoma at definitive excision was found in 131 (42.5%) of all surgical specimens: 95 (40.6%) shave biopsy patients, 32 (60.4%) punch biopsy patients, and four (19.0%) excision biopsy patients. Recommendations for excision margin or sentinel lymph node biopsy changed in 15 (6%) shave biopsy patients and five (9%) punch biopsy patients.

Conclusions: Shave biopsy is the most frequent method of diagnosis of cutaneous melanoma in the modern era. While shave and punch biopsies may underestimate true T-stage, there was no difference in need for reoperation due to T-upstaging based on initial biopsy type, supporting current diagnostic practices. Partial biopsies can thus be used to guide appropriate treatment and definitive wide local excision when adjusting for understaging.

Keywords: Melanoma; Partial biopsy; Shave biopsy.