Shave biopsy of pediatric melanocytic tumors compromises staging and therapy planning

e21576 Background: Melanoma is the dominant skin cancer of pediatric patients, and accounts for 1-3% of pediatric malignancies. The prognosis for both adults and children with melanoma correlates with stage at diagnosis, and initial Breslow depth is a critical determinant. Kaplan-Meier melanoma-specific survival curves show survival rates ranging from 98% (T1a) to 75% (T4b) at 10 years for adult patients with stage I and II disease at diagnosis. Pediatric patients are known to present with thicker primary melanomas as compared to their adult counterparts. The preferred biopsy method of the American Academy is Dermatology for melanoma is excisional, however partial shave biopsy is most frequently performed in children, given its simplicity, efficiency, and often low clinical suspicion for cutaneous malignancy. Despite the ease of this biopsy technique, shave biopsy has a high rate of base transection, reducing accuracy of microstaging, which is crucial for therapy planning. Methods: Retrospective chart review evaluation of the potential effects of biopsy method on staging, surgical recommendations, and treatment approach for pediatric patients with melanocytic tumors. Results: Data was available for 91 pediatric patients with a spectrum of melanocytic tumors ranging from atypical with unknown malignant potential, to melanoma. Patient characteristics including gender, age at biopsy, biopsy method, status of biopsy margins, recommendations for re-excision, sentinel lymph node biopsy, and treatment plan were collected and analyzed. There were 48 females and 43 males with age range 1—22 years (mean 10 years). Sixty-eight of 91 (75%) tumors had a positive margin (deep, peripheral, or both) on diagnostic biopsy, 52/68 (76.5%) were obtained using shave method. Evaluating the deep margin specifically, 50/91 (55%) tumors had a positive deep margin, 46/50 (92%) of which were obtained using shave method. No tumor evaluated by punch had a positive deep margin (0/18). Of all shave biopsies, 77% had positive deep margin as opposed to only 13% using alternative biopsy methods. In 10/91 (11%) patients, surgical recommendations were changed based on inaccurate microstaging and positive deep biopsy margins, 9/10 (90%) of these patients had undergone shave biopsy. Most (8/10) patients had melanoma, the remaining 2/10 had highly atypical spitzoid tumors in which melanoma could not be ruled out. Conclusions: Pediatric patients with melanocytic tumors most commonly underwent shave biopsy as the initial diagnostic biopsy method. This method of biopsy was associated with higher incidence of positive margins at diagnosis and more aggressive definitive surgical management. These findings suggest that more routine use of excisional biopsy in pediatric patients with lesions being evaluated for malignancy could decrease the incidence of inaccurate microstaging and reduce the need for more aggressive definitive surgical management.