Comparative genomic hybridization for the diagnosis of melanoma

Despite advancements in protocols, a subset of melanocytic lesions continues to pose diagnostic challenges. This is particularly true in the pediatric population where certain congenital nevi mimic melanoma. Recently, comparative genomic hybridization (CGH) has been utilized to support diagnoses of melanocytic lesions based on DNA copy number changes. Because distinct differences in copy number changes have been shown to occur in malignant melanoma and benign nevi, CGH can be a useful adjunct when diagnosis based on histology alone is indeterminate. The authors discuss the benefits of using CGH to aid in the diagnosis of melanocytic lesions that are difficult to characterize as malignant or benign based on clinical and histologic features alone. This paper presents a brief clinical report and review of the literature. A 13-year-old Caucasian male presented to an academic tertiary care medical center after a shave biopsy unexpectedly revealed malignant melanoma with positive deep margins. Following complete excisional biopsy, the diagnosis of malignant melanoma with depth of 0.92 mm was confirmed, both by the home institution's pathologist and by consultant dermatopathologists at two separate academic tertiary medical centers. Sentinel lymph node biopsy revealed a small focus of metastatic melanoma, this lead to a left-sided modified radical neck dissection. All nodes removed were negative for disease, and surgical and postsurgical care was uncomplicated. Before proceeding with interferon therapy, CGH was performed on the tissue from the primary lesion. Other than a slight amplification of chromosome 16p, no other aberrations were detected favoring a benign lesion. Ultimately, the diagnosis was amended to compound melanocytic nevus of the nose with benign nevus cell rest in the sentinel node. While histopathologic evaluation is the current gold standard for the diagnosis of melanoma, there are many cases where it is inaccurate. The use of CGH in the evaluation of histologically equivocal lesions may allow certain patients to avoid invasive procedures and associated morbidities. The authors propose that, in these select diagnostically challenging cases, tissue analyses by CGH may be beneficial before proceeding to more invasive procedures such as sentinel node biopsy and complete lymphadenectomy.