Induction of Cutaneous Melanocytic Tumours by N-Ethyl-N-Nitrosourea in the Mongolian Gerbil (Meriones Unguiculatus)

Abstract

There is an increasing incidence of malignant melanomas in man but the factors involved in the development of this tumour are not well characterized. Two questions are of special interest; the first of which concerns the relationship between melanocytic nevi and melanomas. Most individuals have melanocytic nevi, but only few people develop malignant melanoma. Many patients report the sudden growth of a longstanding mole, but it is not assumed that benign nevi become malignant. More likely, melanomas may exist for years with minimal increase in size, until they show themselves by rapid growth [9]. The other major point of interest focuses on environmental factors possibly involved in the etiology of melanoma in man. Sunlight is considered as the most important single cause [7], although a large proportion of tumours are located at sites not usually exposed to ultraviolet irradiation (e.g. eye, vulva, gastrointestinal mucose, brain). Therefore, a systemic effect of UV-irradiation has been postulated [6], but conclusive evidence for malignant transformation by this mechanism is still lacking. Melanomas have been observed following exposure to chemical carcinogens both in man [1] and experimental animals [3] and the possibility exists that malignant transformation of melanocytes may be due to systemic rather than topical effects of environmental factors.