ABSTRACT
BACKGROUND: Diffuse melanosis cutis (DMC) is a rare presentation of metastatic melanoma characterized by a progressive blue-gray discoloration of the skin and mucous membranes. OBJECTIVE: To foster a better understanding of the clinical presentation, histological findings, and pathophysiology underlying DMC. METHODS: A systematic review of the literature was completed utilizing MEDLINE, CINAHL, Embase, and Google. Data were extracted using a protocol-driven spread sheet with all statistical analyses completed using SPSS. RESULTS: The review identified 68 original cases of DMC. The mean time from diagnosis of melanoma until development of DMC was 11.48 months (95% confidence interval [CI]: 0-48.16). The mean time to death following the onset of DMC was 4.43 months (95% CI: 0.00-11.11). Histological findings were relatively consistent demonstrating intracellular and extracellular melanin deposition in the dermis, with a pronounced perivascular distribution. The pathophysiological mechanisms underlying DMC could not be definitively elucidated; however, it is hypothesized that the melanin precursors, melanin, and melanosomes liberated by cytolytic metastatic melanoma deposits are phagocytosed by dermal histiocytes, manifesting clinically as diffuse melanosis. LIMITATIONS: The cross-sectional nature of case reports, paucity of cases of DMC, and heterogeneity in reporting limit any conclusions being drawn regarding the pathophysiology of DMC definitively. CONCLUSION: DMC heralds a poor prognosis for patients with metastatic melanoma and affected patients should be made aware of the implications of this condition on survival.