Assessment of lipid and pigment content in suspicious melanocytic lesions to improve melanoma detection.

Melanoma is a highly aggressive form of skin cancer and the most frequent lethal malignancy diagnosed by dermatologists. Although there have been advances for predicting melanoma prognosis, there are few highly sensitive and specific diagnostic tools for clinically evaluating suspicious melanocytic lesions prior to biopsy. We have recently determined that alterations in cellular lipid and pigment content are associated with tumor progression and melanoma metastasis. Here, we seek to determine if lipid droplet and pigment content assessments near the skin's surface are able to distinguish benign from malignant melanocytic lesions. We obtained 14 benign melanocytic lesions, classified as Melanocytic Pathology Assessment Tool and Hierarchy for Diagnosis (MPATH-Dx) class 1, and 22 malignant melanomas, classified as MPATH-Dx class 4 or 5, from Boston Medical Center. The malignant melanomas had an average greatest thickness of 1.8 ± 2.1 mm with 7/22 biopsies showing the presence of ulceration. Tissues were stained with the Fontana Masson stain to detect pigment or immunohistochemically stained for adipophilin, the main protein component of lipid droplets, to detect lipid droplets. Pigment and lipid droplets were quantified using ImageJ and CellProfiler, respectively. We found no significant difference in total pigment area between benign melanocytic lesions and malignant melanoma, and a 66% decrease in lipid content and 68% reduction in lipid/pigment content between benign melanocytic lesions and malignant melanoma (P < 0.05). Our results suggest that lipid content and lipid/pigment content ratios may distinguish benign and malignant melanocytic lesions, which may be useful as a diagnostic tool for histopathologically challenging pigmented lesions.