Depigmentation: Its significance in patients with melanoma

Abstract

Malignant melanoma is the leading cause of death from tumors of the skin, and its incidence is rising at an alarming rate.1,2 The American Cancer Society estimated that melanomas account for 1–2% of all cancer deaths.3 The prognosis for a malignant melanoma is directly related to the thickness of the tumor as measured by the Breslow or Clark technique.4 Although the incidence of melanoma has increased, fortunately there also has been an improved survival rate. Patients with clinical stage 1 disease (no clinical evidence of tumor in regional lymph nodes) and a tumor depth of less than 0.75 mm have a 95–100% 5-year survival rate5 if the malignancy is properly excised. The improvement in cure rates or longer survivals probably results from earlier diagnosis made possible by public awareness campaigns, rather than from advances in medical or surgical therapy.62,73 Those patients with a deep tumor and/or advanced disease (stage 2, regional lymph node metastases; stage 3, distal metastases) have a dismal prognosis. Treatment of patients with metastatic melanoma is disappointing. Surgical ablation of tumor in regional lymph nodes (clinical stage 2) gives a 20% 5-year survival rate, but even these patients cannot be assured of a cure. Melanomas can recur as long as 20 years after excision.There have been numerous isolated reports of depigmentation occurring in association with cutaneous or ocular melanomas.8–18 This is a rather paradoxical association. Melanoma is an uncontrolled proliferation of malignant melanocytes. In contrast, depigmentation is an abnormal destruction of benign melanocytes. That the two phenomena occur together has attracted attention in recent years.20–23 It has been suggested that patients with metastatic disease who develop a vitiligo-like depigmentation survive for longer periods than might ordinarily be expected. This observation led to speculation that induction of vitiligo might be considered after resection of the primary melanoma to prevent metastases and to enhance survival.24In this chapter, the literature on the subject of melanoma and depigmentation is reviewed. Also, the question of whether their joint occurrence influences the longevity of survival is examined. Various examples of similar observed phenomena within the animal kingdom are reviewed. Lastly, some attempt is made to explain the pathogenesis of this interesting phenomenon.